Our sun is a single star system, but using new technology, scientists are discovering double – and even triple! – star systems

The planets of the sun revolve around a single star, just like the planets in many systems. Revolving around a single star is the general principle, but scientists have recently discovered planets that revolve around two stars, without causing any irregularities. Planets that revolve around two stars are accepted as a new class of planets and according to calculations their numbers in the Milky Way galaxy are estimated to reach at least ten million.

How can this be possible? A planet traveling around two stars enters the gravitational field of each star during its motion, and its velocity and orbit constantly changes.

If stars can shade (eclipse) each other, it is possible for one planet to shade one or two stars. When this event takes place, the planet and stars orbit on the same plane. This intersection on the same orbital plane means that the planet and star have passed in front of each other; we can measure this due to a reduction in the amount of light emitted by the star. If the distance between the two stars is too long, these stars act as if they are isolated from each other. In that moment, the planet that is moving on one of the star’s orbits does not feel the effect of the other star. These are called S-type planets and dozens of them have been discovered in the last decade.

Interesting events take place when stars get close to each other. In such cases, the time required for stars to make a complete revolution around each other is described in days or weeks. The ability of a planet to move in “braided pathways”^[1] that will allow a stable orbit around two stars that are so close to each other cannot be a coincidental event without fine adjustments.

S-type systems are only one type of double-star systems. In P-type systems, the planet revolves around the two stars simultaneously. For this type of planet to travel in a stable orbit, the orbital distance from the stars must be longer than a critical distance. If it is closer than this critical distance, the planet’s orbit becomes progressively unstable, and it is either pulled towards one of the two stars and collides, or gets thrown into outer space. This critical distance is 2/3 of the star’s magnitude.

In a system of a single star and planet, the transit of the planet occurs as if the light makes a periodic movement, such as when a light house rotates around itself. These passes allow us to detect stars. Double-star planet systems are another example of this. It is not easy to estimate the movement of an object consisting of three elements. In a single-star system, the star’s movements are stable; thus, it is easy to estimate the movement of a planet. Yet in a double-star system, the distance between the two stars is much shorter than their distances to the planet; for this reason, these stars revolve at a higher speed around each other than the planet revolves around them. This means that the planet’s rotation is difficult to predict.

As a result, the planetary movement of a double-star system will not be periodical; different than that of a single-star system, the time of transit passes will vary according to the relative motion of the planet to the star. If the planet and the star it revolves around are moving in the same direction, the transit pass time will be longer; but if the star is located at the other half portion of the orbit and traveling in the opposite direction, the transit passing time will be much shorter.

The Kepler spacecraft and telescope that NASA launched in March 2009 is designed for detecting planets that cause reductions in the light of stars when they are passing in front of them. Today, more than two thousand twin star systems that display eclipses have been discovered. Two planets that revolve around stars eclipsing each other every 7.5 days were discovered and called the Kepler-47 system. Along with these double star systems, a triple-star system has been discovered through the Kepler telescope; the properties of this system are extraordinary.

Among these, planet Kepler-47b of the inner region completes its voyage around its stars in less than 50 days. In addition, this planet, which is not visible directly, is predicted to be a very hot planet. Since a foggy layer inhibiting its visualization is found to have formed as the result of methane gas combusting in its hot atmosphere. Kepler-47b, which is three times bigger than the Earth’s radius, is the smallest planet among those that have been discovered in two-star systems.

The planet Kepler-47c of the outer region completes its one full tour around its twin stars in 303 days and it moves in a region that is described as the habitable zone in the Milky Way galaxy. There can be liquid water present on the surface of a planet in the habitable zone. However, just being in this zone does not totally mean that the place is suitable for life. Kepler-47c is predicted to be slightly bigger than Neptune and to have an atmosphere composed of thin and bright water-vapor cloud.

Reference

William F. Welsh, Laurance R. Doyle, “Worlds with Two Suns,” Scientific American, October 2013, pp. 40-47.

S- And P- type planets traveling around two stars

Kepler-47c exists in the habitable zone and liquid water is predicted to be present on its surface.

A representative image of the Kepler 16a/b based on acquired data.

^[1] The Qur’anic verse “By the heaven full of braided pathways, surely you are in contradicting views”(Adh-Dhariyat, 51:7-8) sounds like pointing to this phenomenon.

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In order to find answers to these questions, let’s consider ourselves sitting at home after a long, tiring day. Are we aware that we are moving very fast even at a moment when we seem to be resting? When we travel by bus, we are motionless from the standpoint of a sitting passenger, yet have a velocity compared to an outsider standing on the sidewalk. The trees lining the road seem to be going backwards, but they are fixed to the ground with no speed. Therefore, velocity is relative and we in fact move at different speeds while sitting at home depending on the objects of reference. We have a zero velocity relative to our guests sitting with us on the couch, but have various speeds compared to the center of Earth, the moon, the sun and the center of the Milky Way galaxy. Not only us, but all existence in the universe has a movement, or oscillation. This movement is usually in the form of a revolution for objects of important mass and as a vibration for particles with smaller masses.

The shining celestial bodies of the cosmos rotate around themselves like whirling dervishes. They revolve around other heavenly bodies or around their common center of gravities, such as pilgrims revolving around Ka’ba in Mecca. The gravitational force set in the universe pulls all objects towards each other. This gravitational force indeed pulls all masses together; however, it is counterbalanced by the motion of revolution given to grand heavenly bodies. As a matter of fact, everything is moving: a solar system with its planets, moons, and comets; the Milky Way galaxy, along with billions of stars, nebulas, galaxies, interstellar dust, gas clouds, and other celestial objects… all are moving in a giant rotating motion like a carousel. In this article, you are going to find some of the scientific findings of our revolving planet, the sun, and the universe, and how some verses in the Qur’an sound miraculously relevant to them.

The Earth’s motion

First of all, we have a velocity stemming from the Earth’s rotation. People living on the equator travel approximately a thousand miles per hour in reference to the center of the globe due to this rotation. While people on the poles never gain any distance over 24 hours, people on the equator travel nearly 23,800 miles! Inside a plane, because we move at the same rate as the plane, we cannot feel its speed. In a similar way, since we move at the same rate as Earth, we cannot feel the globe’s movement.

There are many benefits associated with the Earth’s rotation. The delineation of day and night, atmospheric jet streams, oceanic currents, and similar events rise from the rotation of Earth around its axis. For instance, it causes the warm water currents of the Gulf Stream to reach England, generating a warm and rainy climate.

There are verses in the Qur’an that point to the globular shape of the Earth and its rotation around its axis and revolution around the sun:

“He has created the heavens and the Earth with truth. He wraps the night around the day, and He wraps the day around the night. And He has made the sun and the moon subservient (to His command), each running its course for a term appointed (by Him). Be aware! He is the All-Glorious with irresistible might, the All-Forgiving.” (Az-Zumar 5)

Yet another verse furthers this point:

“It is He Who has created the night and the day and the sun and the moon. Every one (of such celestial bodies) floats in its orbit.” (Al-Anbiya 33)

The verb “wrap” is usually used for round objects, and the perpetual arrival of day and night are only possible with a circular planet. The Earth’s rotation leads to different days, on the micro level, and different seasons, on the macro level. The Qur’an concisely summarizes all these physical events with the simple phrase, “wrap the night around the day.”

The Earth’s primary motion is around the sun. We are roughly 93 million miles away from the sun and we make this orbit, which is nearly 584 million miles, every 365 days. According to the center of the sun, our average velocity on this orbit is approximately 66 thousand miles per hour.
In addition, other planets travel around the sun via different orbits and speeds, each moving on a separate plane. For a moment, it is significant to visualize the sun, which is more than a million times larger than Earth, with its planets and other viscera revolving around it via no visible bond between them.

The movement of the sun

As stated earlier, when we travel on a bus, we observe the trees and buildings near the road going backwards even though we are the ones moving. In a similar way, we see the sun as revolving around us, though in fact the Earth is the one moving. In the Qur’an, the chapter of Al-Anbiya, the verse reading, “each running its course,” is about the creation of the sun and moon, clearly pointing to their movements. Unfortunately, the verse that reads, “A(nother) clear sign for them; And the sun runs the course appointed for it for a term to its resting-place, for the stability of it(s system)…” (Ya Sin 38) was misunderstood as the sun revolving around the Earth. However, we know today that our sun is one of a couple hundred billion stars in the Milky Way galaxy. As such, it both rotates around itself and revolves around the center of the Milky Way galaxy, and confirms the miraculous declaration of the truth in the verse.

In addition, the sun also has a secondary movement inside the local star cluster towards a certain direction. We can explain this with an example: the atmosphere is in motion along with the Earth. Each particle and particle set that makes up the atmosphere not only moves right and left, but also has a total revolution around the Earth. The sun behaves in a similar way within the star cluster and around the center of the Milky Way.

How are we going to define the velocity of the sun? We can determine the sun’s speed by referencing a constant point depending on the average velocity of stars in the section of the galaxy that we inhabit. The sun, according to a local constant point, travels towards the shiny Vega star in the Lyra constellation with an average speed of 43 thousand miles per hour.

Apart from their individual movements, the stars in our galaxy also revolve around the galactic center. The velocity of this movement depends on the star’s mass and its distance to the galaxy’s center. The sun completes one loop inside the Milky Way galaxy every 225 million years. It has completed a total of 20 tours around the galaxy’s center since the Earth’s creation. Our Earth, which moves along with the Sun, travels around the galaxy’s center at nearly 492 thousand miles per hour.

The motion of the Milky Way galaxy

Our galaxy is one of the billions of galaxies in known space. Galaxies are the biggest known structures. The universe expands and galaxies move away from each other, conforming to the meaning of the verse, “And the heaven, We have constructed it mightily; and it is surely We Who have vast power, and keep expanding it” (Adh-Dhariyat 47). Our galaxy, along with nearby galaxies, is pulled towards the Leo and Virgo constellations. The cause of this attraction is not understood yet.

Since all galaxies are moving, how can we determine the velocity of the Milky Way galaxy? As is known, the entire universe is filled with cosmic radiation as a remnant of the Big Bang. When this radiation is taken as a reference, the Milky Way travels at around 1.3 million miles per hour.

At the moment, when we think we are sitting in place, we are actually moving around the center of the Earth, sun, our local star cluster, the center of the Milky Way galaxy, and also moving away from other galaxies. We have velocity in relation to all of these movements. The revolution of the universe is also a fact verified by the Divine word: “I swear by the heaven ever-revolving” (At-Tariq 11).

Astronomers have discovered a planet with the longest known orbital period. Exoplanet Kepler-421b has been identified through the Kepler observatory, a space-based telescope. It circles its star once every 704 days. More than 1800 exoplanets have been discovered so far, but compared to Kepler-421b, those had much shorter orbital periods, like a few weeks or even a few days. The host star for Kepler-421b is much like the sun, but it is little bit smaller and relatively cooler. With an orbital distance of 177 million kilometers, Kepler-421b gets about one-fourth the light from the host star as the Earth receives from the sun, which makes the exoplanet as cold as -100 °C. The unusual orbit places Kepler-421b beyond the “snow line,” which is accepted as the dividing line between rocky and gaseous planets. Outside of the snow line, water condenses into ice grains that stick together to build planets known as “gas giants.” Since gas giant planets are very close to their stars, theorists believe that many exoplanets migrate inward early in their history. However, Kepler-421b is the first example of why such migration may not be necessary.

Sunflowers’ internal clock

Plants are known to grow toward the sun to maximize the amount of energy they absorb. Sunflowers (Helianthus annuus) show the most fascinating behavior during summer, when they follow the sun as it rises in the east every morning and sets in the west every evening. In a recent study, scientists challenged the obvious explanation for this plant’s behavior: are flowers solely responding to sunlight or are there other unknown mechanisms at work? They designed a clever yet simple experiment where they grew sunflowers in chambers with a fixed overhead light that was continuously on. Surprisingly, for several days, the sunflowers under constant light kept moving as if the sun were rising in the east and setting in the west. This unexpected result suggests that sunflowers were not responding only to the direction of the light but also to an internal biological clock. Furthermore, they discovered that sunflowers bend when one side of the stem grows faster than the other. For example, the west side of the stem seems to grow faster to bend the plant towards the east in the morning. Scientists now hope to understand how an internal biological clock in sunflowers has the opposite effects on opposite sides of the stem. Sunflowers are not the only plants performing this diurnal dance; other agriculturally important crops such as soybeans and cotton exhibit the very same behavior. Solar tracking is known to boost plant yield and discovering the mechanisms of how plants track the sunlight might have important implications for improving global agricultural yields.

Friends linked by genes

It is a common observation that close friends look alike. Even centuries ago, Plato noted the tendency that good friends usually have similar appearances. Recently, a group of geneticists took this idea even further and suggest that people on average tend to choose friends who are genetically similar. The study provided convincing evidence that we have more DNA sequences in common with the people we pick as friends than we do with strangers in the same population. Researchers performed a genome-wide analysis of approximately 1.5 million markers of gene variations from 1,932 subjects of the Framingham Heart Study, which is one of the most comprehensive genetic databases. They identified 1300 pairs of non-relative friends and compared their genetic information to each other. The analyses showed that friends share similar genetic variations (around 1% genomewide), to the degree that it is as if they have the same great-great-great-grandparent – in other words, as if they were fourth cousins. Notably, friend pairs seem to have the greatest similarity in the genes that are responsible for a sense of smell and they show the most difference in immunity-related genes. Friendship entails spending a lot of time together and looking out for each other. Odors are strong behavioral cues in human psychology and people with similar olfactory preferences might like to prefer living or hanging out in similar environments. Likewise, it is potentially a big advantage that friends don’t get infected from the same microbes at the same times, so that one of them can take care of the other. As much as these anthropological implications are merely speculations with many caveats – and despite there being many obvious social, ethnical, and cultural factors that help determine friendships – the genetic basis of friendship and other social interactions may hold answers to at least some of the mysteries of human behavior.

Meinecke et al. Turbulent amplification of magnetic fields in laboratory laser-produced shock waves, June 2014, Nature Physics.

A supernova is the explosion of a massive star which releases a burst of radiation that can be as bright as 10 billion suns. Such a massive amount of radiation can shine throughout the entire universe for several light-years. Supernovas are triggered either when the fuel within a star ignites or when a star’s core collapses under extreme gravitational forces. Supernovas have already taught us very important lessons about the history of the universe. For example, these explosions have provided solid evidence that the universe is expanding. Supernovas can also tell us a lot about how old stars die and how new stars are born. When a star goes through a supernova explosion, it leaves behind a skeleton made of expanding dust and gas that scientists call a remnant. These star-remnants spread around space. They might end up on earth or other planets, or they could form the energy source of a new star. Since the best way to understand supernovas is to actually explode a star, researchers recently developed a technique to simulate small-scale supernovas in a lab environment. To do this, scientists used lasers that are 60,000 billion times more powerful than a laser pointer. They focused the laser beams on a thin carbon rod inside a gas-filled chamber. The lasers heated the chamber to over 1 million degrees Celsius, which caused the carbon rod to explode and expand out through the low density gas – just like how exploding stars speed through space. The experiment revealed that as the blast passes through the grid, it becomes irregular and turbulent. They also noticed that the magnetic field was dramatically higher within the grid than without, suggesting that the magnetic field was amplified by the generated turbulence. The supernova system developed in this study holds the possibility of helping us better understand how the universe was formed and evolved, and could provide some insight into how magnetic fields were first created.

Young blood: The fountain of youth?

Villeda SA et al. Young blood reverses age-related impairments in cognitive function and synaptic plasticity in mice. June 2014, Nature Medicine.
Sinha M. et al. Restoring systemic GDF11 levels reverses age-related dysfunction in mouse skeletal muscle. June 2014, Science.

Two recent studies of lab mice showed that transfusions of blood from younger individuals reverse the effects of aging in their elders. One research group showed that neural damage of mice with age-related cognitive impairments could be reversed by such transfusions. Alternatively, injecting the younger plasma into the brain was also very effective at repairing neural damage. Another research group showed that blood from younger mice repaired age-related heart defects in older mice. Researchers further discovered that high levels of the protein GDF11, present in the blood of younger mice, were the key for rejuvenation. Researchers proposed that blood from younger mice contains molecules with anti-aging properties that awaken the stem cells of the brain and heart muscles and thus initiate the rejuvenation. These studies are incredibly encouraging for combating Alzheimer’s disease, heart disease, and many other age-related diseases; however, a comprehensive set of clinical tests needs to be conducted before testing the effects in humans.

“Chameleon” plant discovered

Gianoli E. and Carrasco-Urra F. Leaf mimicry in a climbing plant Protects against herbivory. May 2014, Current Biology.

Scientists thought for many years that camouflage and mimicry were only observed in the animal kingdom. A newly discovered wood vine in Chile, Boquila trifoliolata, has been found to transform its leaves to mimic a variety of host trees. B. trifoliolata is the first plant ever shown to imitate multiple hosts. This is a rare trait called “mimetic polymorphism” and it was only previously observed in butterflies. As B. trifoliolata climbs onto a tree’s branches, it changes the color, size, shape, orientation, and even the vein patterns of its leaves to match the surrounding flora. When the same vine crosses over to a second tree, the size of its leaves can even increase 10 times  to match the second host plant. According to scientists, mimicry may protect the vine from plant-eating herbivores such as weevils and leaf beetles. It is perplexing how a plant can distinguish between individual trees and keep changing its physical characteristics. Odors, chemicals, or microbes that are released form host plants are potential candidate mechanisms for this intriguing plant behavior.

A planet that revolves around another star outside our solar system is called an Exoplanet or Extra solar planet. Ongoing studies involving this field are carried out via simultaneous ground and space based missions and observations. Scientists are searching a small portion of the Milky Way galaxy, approximately 3000 light years away, by using ground and space telescopes, along with various other astronomic methods (1). Despite all this technology, the observation area is too big when compared to the size of the object of interest.

It has been calculated that the Milky Way, a disc shaped galaxy, consists of 200 billion stars spread over a diameter of nearly 100,000 light years and a thickness of 1000 light years. When we consider the amount of stars in a single galaxy, and the fact that there are between a hundred billion and one trillion galaxies in the universe, the number of possible exoplanets is likely much larger than those we currently know of.

Classification of exoplanets

Exoplanets are classified according to their physical, chemical, and other characteristics, along with their diameter and mass: Jupiter like; greater than Jupiter; Earth like; greater than Earth

Classifications according to surface and atmospheric temperatures are as follows: Hotter than Jupiter; colder than Neptune; colder than Jupiter; small blue dots or twin Earths.

The presences of free-floating planets which have lost their parent stars because of different formation processes or other factors have also been discovered.

One of the common features of the exoplanets currently discovered is their short distance to the star they revolve around, which is usually less than half the distance between the Earth and the Sun. The known exoplanets are also defined by their faster revolutions in much shorter periods. Therefore, larger planets that are closer to their stars can be observed easily. When these planets are passing in front of their stars, a decrease in the brightness of the star is detected via spectrometers (Figure 1).

Figure 1. Passing of a planet in front of a star and a spectrum of this event.

Radial velocity, one of the methods used to discover exoplanets, relies on the observations of a star’s kinetic fluctuations. The proximity and size of a revolving planet leads to slight changes in location and velocity of a host star. As a result of this, the star gets closer to earth and then becomes more distant, which is observed as the Doppler shift of spectral line color waves. 75 % of all known planets have been discovered using this method (Figure 2).

Figure 2. Doppler shift – radial velocity

Earth-like planets or habitable places

In an official NASA report in December 2011, the discovery of an Earth-like planet was announced for the first time. This planet, named Kepler 22b, is 600 light years away and remains the most similar one to Earth among the known heavenly bodies. The distance of Kepler 22b to its star shows a high possibility for the presence of a habitable zone.

So what does this mean?

Earth is such a special home for us humans that everything here has been assigned to serve us with delicate calculations. Factors such as the Earth’s mass, gravity, distance to the Sun, rotational and revolution velocity, chemistry, thickness of the atmosphere, magnetic shield, hydrosphere/land ratio, ecological balances, and average temperature are all perfect for biological life.

Earth revolves in such a region and position that a majority of the planetary water is in a liquid state and is not ice or vapor.Thedistance of the habitable zone to our Sun is between 135,000,000 – 225,000,000 km. Earth revolves at a 150,000,000 km distance to the Sun. The value of a habitable zone for each planet depends on the diameter, mass, heat and radiation strength of the host star. In other words, aside from the similarity of an exoplanet to Earth, a classification of its host star with in terms of size and age is also important.

Kepler 22b owns the title as the first planet to match the criteria above with its following features:

• Has a radius 2.4 times bigger than Earth
• Revolution time is 290 days (365 for Earth)
• 15% closer to its star compared to the Earth-Sun distance
• The size and surface temperature of Kepler 22b’s host star is very similar to that of the Sun’s
• The surface temperature of the planet is 22 C
• The size of the habitable zone for Kepler 22bis 133,500,000 – 240,000,000 km (Figure 3).

Figure 3. Comparison of the solar systems of Kepler 22b and Earth.

Aside from these similarities, it is noteworthy to report the problems that scientists encountered regarding Kepler 22b:

• The unknown presence of water on the surface
• No information on the gaseous contents of the atmosphere.
• The gravitational force is 2.5 times greater than on Earth.
• Rocks constitute the surface instead of soil.

The hardest part is that Kepler 22bremains 600 light years away from us. This means it would take us 11 billions years to get there with today’s fastest spacecrafts. Who knows when we will be able to decrease this time with the advent of superior technology.

What do religious scholar say about life in outer space?

Among His manifest signs is the creation of the heavens and the earth, and that He has dispersed in both of them living creatures. And He has full power to gather them together when He wills. (Ash-Shura 42:29)

While interpreting the Qur’anic verse above, Fethullah Gülen notes the following:

“Since the earliest times, this verse has been taken as a proof for the view that there are living creatures, whether resembling human beings or not, in the places other than the earth. This view may be true. The second part of the verse, ‘He has full power to gather them together when He wills,’ has been understood that these creatures and human beings will possibly come together either in this world or in that of the other creatures. … there may be earth-like globes in the heaven where creatures resembling earthly ones live.” (Gülen 2012, 272-273)

“Perhaps people will not be able to reach those places individually or as a whole generation, but this can be achieved by mankind as a species. In other words, when the Divine Will manifests itself in that direction, humans here can encounter those other life forms.” (Gülen 2007, 232)

This commentary reflects what Bediuzzaman Said Nursi had said decades ago:

“The earth, although much smaller than other heavenly bodies, is so densely inhabited by living creatures that even its grossest and most rotten parts are full of living things, such as micro-organisms. This shows that those infinite firmaments, with their numerous stars and constellations, are inhabited by conscious, living beings …” (Nursi 2010, 530-531) 29th Word, First Aim, First Fundamental)

Nebiyev is a professor of physics in Azerbaijan.

References

• http://kepler.nasa.gov/
• http://planetquest.jpl.nasa.gov/
• http://en.wikipedia.org/wiki/Habitable_zone
• Gülen, M. Fethullah. 2007. Kendi iklimimiz, Istanbul, Nil Yayinlari.
• Gülen. M. Fethullah. 2012. Reflections on the Qur’an: Commentaries on Selected Verses, NJ: Tughra Books.
• Nursi, Bediuzzaman Said. 2010. The Words, (29th Word) NJ: The Light, Inc.
• Chris Kitchin Exoplanets: Finding, Exploring, and Understanding Alien Worlds- (www.springer.com/series/6960)-2012
• Mercy, G., P. Butler et al. 2005. “Observed Properties of Exoplanets: Masses, Orbits, and Metallicitie”.. Progress of Theoretical Physics Supplement, Vol. 158, No. 24-42.

The life of a star is affected by two main factors: while gravitational forces pull the gas contained in the star towards the center, pressure that is generated by the nuclear fusion which takes place in the center pushes the gas outwards. When a star runs out of fuel, gravitational forces take over and it results in the sudden collapse of the star. As a result of this sudden collapse, oversized stars get dispersed into space through a massive explosion. These explosions are called supernovas.

It may be a hard task to predict beforehand whether a particular star will be dispersed in the shape of a supernova. When explosion takes place, dispersal of the supernova happens so fast (within 2-3 minutes) that it is almost impossible for astronomers to capture the exact moment of the explosion. After the initial explosion, there is extreme brightness and this lasts for a couple of weeks. This event when observed from a distance is taken as if the birth of a new star. Later on, the brightness gets dimmer and eventually disappears. Astronomers only have to investigate the remnants of the supernova from this point on. In some supernovas, stars get completely destroyed by dispersal into space (Type 1), but in some, a neutron star is left behind (Type 2).

Type 1 supernovas

Even though supernovas are known to be explosions of oversized stars, smaller ones can also explode and still be considered as a supernova. Interestingly, supernovas of smaller stars are even brighter. Stars with a mass less than the total mass of eight suns turn into a red giant at the end of their lives. After the red giant stage, exterior layers of the star get blown into space and it turns into a white dwarf with a mass equal to 0.6 times the mass of the sun. If a hydrogen rich material from a large star nearby flows over this white dwarf, it turns the white dwarf into an explosive composition. The white dwarf reaches the brightness of a million stars by exploding. These types of explosions are called novas.

Even though we see stars in the sky as individual bodies, 60% of them are found in pairs. An amazing star bomb is generated when the two white dwarfs in a star duo join one another. These massive explosions of White Dwarfs as a result of their complete dispersal into space by thermonuclear chain reactions can even be observed from distant galaxies. They always explode at the same mass threshold and since the amount of released energy is the same, they are used as standard light sources by astronomers. When the resulting star (formed after the two dwarfs unite) exceeds the critical size of 1.4 times the mass of the sun, it starts to collapse on its own with gravitational forces. Central pressure increases during this collapse and with the start of thermonuclear reactions, it eventually builds up internal pressure.

Since the outer layer of the star is hardened, it completely disperses into space with an enormous explosion. Remnants left behind by the explosion begin to expand very rapidly (at a speed of 30,000 km/s). Brightness more powerful than a billion stars is generated during the energy release of Type 1 supernova. In other words, the energy supernova released for a couple weeks is much greater than the total lifetime energy released by the sun. The initial strength of the supernova diminishes after a few weeks. As the supernova expands, its brightness decreases proportionately.

Ultimately it becomes a gas and a dust cloud known as a nebula.

Supernovas may be observed in different levels of brightness depending on the distance of the star to the earth. Closer supernovas can be seen as big and bright as the moon however distant ones can be observed like a bright, dimmed star, or may not be visible at all.

Type 2 supernovas

Stars with a mass between 8 and 50 times the mass of the Sun go through a series of changes a lot faster than smaller stars, eventually turning into a neutron star. During these kinds of changes, all stages of nuclear fusion takes place, as first hydrogen, then in order, helium, carbon, nitrogen, oxygen, silicon, and iron are synthesized in the stars. Iron is found in the center and other elements surround it in layers. When such a star runs out of fuel, nuclear fusion ends. The finale of nuclear fusion reactions at this stage is characterized especially with iron representing a stable nuclear structure.

When the reactions are over in the center, the iron core collapses on its own with gravitational forces. Because of the intense pressure on iron, protons of this atom unite with its electrons forming neutrons. This event takes place very fast and also particles called neutrinos are emitted. These particles apply an outward pressure on the exterior layer of this star which has already turned into a super red giant, causing burst of external layers into space. This event is described as being a Type 2 supernova.

Remnants of supernovas

Supernova remnants are radioactive. In fact, a major portion of the light emitted by a supernova is derived from radioactivity. Furthermore, supernova remnants are very powerful sources of cosmic radiation. These remnants can be observed in two forms: the first form is directly observable gamma rays when high energy particles including protons and electrons interact with interstellar gasses; and the second form is indirectly observable radio waves when high speed electrons emitted via explosion get accelerated at the interstellar magnetic fields. Gases rich in heavy elements that constantly expand are left behind after supernovas. Because of abundant neutrons in the environment, elements heavier than iron are also synthesized. This richness is entirely thrown into the interstellar place. All of the heavy metals including iron are thought to have joined the solar system through a supernova explosion. “We have sent down iron” in Chapter 57 of the Holy Qur’an may refer to the dispersal of iron and other elements into the space through supernova explosions.1

Sun rising from the West

What happens when a star nearby our system explodes as a supernova? A second sun appears in the sky. Does such a supernova explosion disrupt the conditions on the earth via causing a similar or bigger impact than the sun on the planet in terms of light and heat? If such an exploding star happens to be in the west, can we consider it as the sun rising from the west? Considering that supernovas are strong light sources, a second sun appearing in the near sky for a couple of weeks will have significant impacts on planet earth.

At first, day and night would disappear. Planetary temperatures would rise to lethal degrees. Evaporation of seas and oceans may cause worldwide flooding. Local temperature rise caused by the two suns may generate severe storms. Remnants of the star as it loses brightness after a couple of weeks can color the sky blood red as described in the verse: “And finally when the heaven is rent asunder, and it becomes rosy like red hide!” (Rahman 55:37). Events pointing to doomsday as described in apocalyptic verses can take place. Surely God knows the best of everything.

Notes

1 For a similar discussion on a possible connection of this phenomenon with this Qur’anic verse, you may refer to a previously published article titled “Supernova Explosion and a Miracle of the Qur’an” by Nuh Gedik (The Fountain #54, 2006).

References

Silk, Joseph. 1997. A Short History of the Universe, W. H. Freeman.

Zeilik, Michael. 1994. Astronomy: The Evolving Universe, New York: John Wiley & Sons Inc.

]]> https://fountainmagazine.com/all-issues/2013/issue-92-march-april-2013/rising-and-collapsing-worlds-in-galaxies-march-april-2013/ Fri, 01 Mar 2013 00:00:00 +0000 http://107.21.79.195/all-issues/2013/issue-92-march-april-2013/rising-and-collapsing-worlds-in-galaxies-march-april-2013/

By the time you finish reading this sentence, you will have been carried over the earth, passed the sun, and moved through actual space of 1000 kms! In the time it takes you to ponder upon this, you will have moved another 1000 km through real space. Fast isn’t it? This is the speed at which one arm of our galaxy moves through space every second, and we don’t even feel a thing!

The motion of stars in their dedicated orbits, black holes, nebulas, and infinite number of other phenomena in the outer space display spectacular and equally thoughtful exhibitions thanks to Hubble and other new technologies. An increasing number of studies are thus devoted to stars, supernovas and interstellar space in recent years. Our contemplation of the universe deepens as we accrue more knowledge about it. Just as a cell is the functional building unit of the body, the main building blocks of the universe are galaxies. Just like every other living thing, galaxies will not be around for eternity; they form, develop, and cease within the cosmic laws that are put in place by their Creator.

According latest findings, it is estimated that around 100 billion galaxies exist in the observable universe and that there are galaxies 100,000 light years in size. A year has 31,536,000 seconds. Light travels 300,000 kilometers per second, therefore one light year equals to 946,080,000,000,000,000 (quadrillion) kilometers. Apart from the dispersal of stars, intergalactic distances of galaxies are not much bigger than their own galactic size. For example, the big Andromeda galaxy (the galaxy which is the closest to us) appear from the earth as wide as the sun or moon in the sky and can even be noticed with the naked eye. Latest research in astrophysics revealed that stars are not dispersed equally but rather found together in galaxies as an open system that exchanges energy and matter with its surroundings. A big portion of the galactic space is filled with gas and dust clouds which enable such exchanges to take place. This interstellar stage in which stars are born and die bears vital importance in sustaining and maintaining a galactic presence.

Some amazing characteristics of galaxies

Stars with different masses exist in a galaxy. Smallest one can be one tenth of the Sun’s mass whereas the biggest can be 100 times bigger than the sun. The most important feature of a star in a galaxy is its mass. Brightness of stars increase with their mass and this relation is three dimensional (cubic mass). Therefore if a star is twice as big, it is eight times brighter. Another feature is the relation between the age and mass of a star. The bigger the star, the shorter its life. These big stars live shorter compared to smaller ones despite their giant fuel reserves because they consume it very fast. Similar relations can be observed in the human body, which is an index of the universe, such that overweight people who consume more calories than people with less calorie intake eventually consumes more energy and become subject to deterioration in health and faster aging. The lifespan of a star is inversely proportional with its square mass (1/m2). For example, if a star is twice as massive, it lives only for one fourth of the time. Calculations show that our sun has a lifespan of 10 billion years. Compared to this, if a star is 30 times bigger than sun, it will only live for 10 million years.

The timescale of events that are occurring in galaxies can vary from thousands of years up to millions of years. Time required for the creation of a star is perhaps like a day in a galactic scale. This long time frame is considered short when compared with the age of galaxies. Furthermore, verses in the Qur’an (Al-Ma’arij 70:4) open new horizons in this matter and point out to the fact that time can change depending on different ratios and scales; so a day can indeed vary in length from being 1000 years or 50,000 years.

The movement and behavior of galaxies are quite complicated. Such that even if the galaxy formation process is completed, the creation and expiration process of stars within the galaxy still continues. It takes tens of thousands of years for a gas cloud to collapse inwards under its own gravitational force and become a star under normal conditions. Even five-ten billion years after the creation of a galaxy, it amazes scientists that there is still plenty of gas to remain in the interstellar stage, enough for a star to be born. On the other hand there are galaxies in which star formation is much faster than our Milky Way galaxy. These galaxies are called “starburst” galaxies and new stars are created in variable speeds over a long period of time. The uniqueness that is observed in the specific characterization of animal and plant species can also be witnessed in the creation of stars at different speeds, making spiral galaxies even more mysterious. This is because while a steady and balanced speed in the creation of stars is maintained in spiral galaxies, all the gas and dust available is consumed for the formation of stars in other galaxies. In a galaxy where stars continue to be created, the regions where large stars are created can be observed better compared to other regions in the night sky.

Spiral galaxies

Galaxies are generally divided into three groups: irregular shaped, elliptical, and spiral. Irregular shaped galaxies are composed of many young stars, gas and dust clouds without a definite shape. Elliptical galaxies are made up of old stars and limited number of gas and dust clouds. They are created in different shapes such as round, flat or like a baseball. Spiral galaxies are in the shape of a disc composed of spiral arms extending out of the center as they rotate. Solar system is located inside such a spiral-like galaxy. In these types of galaxies, stars contain spiral signatures. Bright spiral arms found in many images taken of galaxies generally show star forming regions and not the locations of the stars themselves. That is why the exceptional quality of spiral galaxies is hidden in the continual formation and expiration process of stars. Spiral displays which show star creation regions do not revolve along other stars in the galaxy. However spiral galaxies do exhibit a special rotation. Observations point out that spiral signature within the galaxy deteriorates gradually and reshapes in a slower fashion than the galaxy rotation speed. With these new findings, it is possible to say that it is more appropriate to understand galaxies as dynamic systems which change in time instead of being static under the constant and instantaneous intervention and control of the infinite power and wisdom of the Almighty.

One of the most impressive features of spiral galaxies is that the regions where stars are created in the main spiral contain new sublevel spiral patterns. Just like clouds, it is possible for different spiral forms to be created. Sometimes very symmetric spiral arms or rectangular stick-like formations via extensions of spiral arms along with regular spiral looking shapes are generated. Despite this spiral variety, when observed from outside, stars are seen to be surrounding a flat disc and forming together as a giant globular halo. This halo was generated billions of years ago from short and longer aged stars. It is the dimmer region of the galaxy yet this halo is considered to contain most of the galactic material. Stars are located in a fashion that resembles a disc in this halo of dust and gas. The layer of dust slowly rotates around an axis that passes through the center of the halo. This rotation is not coincidental; it is controlled in such a way that the speed of stars nearby do not differ in the rotation speed of the whole disc any more than 10%. In other words, the disc does not have a constant speed. It exhibits flexibility and variations from within. Stars and gas clouds are made to revolve in similar average speeds no matter how far they are away from the center. These notions are confirmed with the use of motion laws that Newton discovered and named after himself.

Numerous types of stars from different age and mass groups exist in the disc section of a galaxy. The age of stars is determined by analyses of the light spectrum that they emit. According to the results from these analyses, the creation speed of stars has been found nearly constant around the disc section in a spiral galaxy. In many galaxies, disc material has been discovered to be around 10% gas and dust cloud and that 80-90% of the rest remains outside the disc in an invisible form, unlike stars and gasses. This is because it absorbs the majority of the light to be reflected. This kind of material is called “dark matter.” It is thought to be a very old black hole, with expired stars or an extremely cold dust cloud or a combination of these. Aside from this, it has been discussed that they are created from neutrinos or undiscovered particles. According to common notion, dark matter as generated by expired stars in the galaxy does not have any relation to the movement of spiral galaxies and their kinetic behavior, it only has gravitational effects.

Gas cloud in the disc is not dispersed proportionately; instead, it is collected in a thin layer. Furthermore, it is understood that these clouds are composed mainly of carbon, silicon, iron and many other elements, and these particles get ripped from surfaces and flown around via star winds or thrown towards interstellar space. Surprisingly, the interstellar space is a scarcely populated place. Even in areas that are considered to be empty, one atom exists in 1,000 cm3, and it can vary from one million atoms to a couple hundred per cm3 in denser regions. The density of interstellar spaces from the highest to the lowest can vary within a factor of a billion. This ratio is much greater than the density difference between air and a piece of rock.

Systems established without thermal equilibrium

Interstellar space is not in a state of thermodynamic balance. Very sizable molecular clouds are constantly shaped and get scattered into the medium. This way material exchange is carried out in between different phases on a smaller scale. Maintenance of a system where different components are preserved in a stable state with no equilibrium is a mystery to all. This elusive phenomenon has been studied by both physicists and chemists for the last 40-50 years. Data obtained so far recommends that two processes are particularly used to establish and maintain stable compounds away from an equilibrium state. The first is that such systems should include material recycling mechanisms between different components. Second is the regulation of processing speed with feedback. These two events should be executed with a balanced fashion so that the amount of material in each composition does not change. Thus, these two phenomena are executed in the most finely calibrated manner in spiral galaxies that can never be possible out of coincidence.

Plasma, one of the phases of matter, is about a couple million degrees Celsius. However, it is a much diluted phase; only one atom exists in a volume of 1,000 cm3. Temperatures rising to these levels are made possible by the energy provided from supernovas. A supernova explosion releases such energy into the space that it forms a hot gas cloud and this starts to expand. This gas cloud releases its electrons into its surroundings as it dissipates. A phase of diluted hot plasma in a bumpy shape is generated as gas cloud expands throughout the matter. One of the reasons that interstellar space took so long to be discovered is because we are still located in a hot bubble. This bubble has a magnitude of 300 light years. Studies so far have mapped this bubble and discovered it to have an irregular shape.

Aside from this, recently a new neutron star was discovered and this star is thought to be remnant of a supernova explosion that created this bubble. It should not be surprising that we are located in such a hot bubble because this only occupies 70% of our galactic disc volume. A supernova is created once every 30 or 40 years in our galaxy. Supernovas have the task of supplying the energy needed to keep the entire interstellar space under a constant pressure. It is an incredible phenomenon to ponder that a habitable planet exists in the depths of a cold space.

Interstellar spaces resemble an ecosystem from a standpoint of events that are taking place inside it. Each galaxy could be viewed as a dynamic system where stars are constantly born and extinguished in the presence of a determined cycle of energy and matter. Events that are executed with Divine wisdom in these heavenly systems (galaxies, stars, interstellar spaces) testify in their own languages to their Creator who fashioned them in the form of an art with wisdom and generously. Galaxies behave as if they are living organisms; they are born like humans and they die like humans. Continual composition and decomposition of galaxies with their contents stand as major proof to the cosmos of present and absent worlds. The heavens and the earth, the stars and galaxies all make up the Divine canvas painted and repainted on the easel of God’s command: “Be and it is.”

References

• Smolin, Lee. 1997. The Life of The Cosmos, Oxford University Press, New York.
• Syed, Ibrahim B. 2003. “Understanding String Theory,” The Fountain, Issue 41, January-March 2003.

Original article: Olzsak T. et al, Science (2012, epub ahead of print)

It has been known by epidemiologists that people who grew up in farms are less likely to acquire immune diseases such as asthma, allergies, inflammatory bowel disease and multiple sclerosis when compared to people living in cities. Such observations have been the roots of “hygiene hypothesis,” which essentially points out the beneficial effects of being exposed to infectious agents. Supporting this theory, a recent study at Harvard Medical School showed that exposure to symbiotic bacteria has a long lasting beneficial effect on the immune system development. “We as a species are not exposed to the same germs that we were exposed to in the past,” said the co-author Dennis Kasper, a microbiologist at Harvard Medical School in Boston. In this study, published in Science, the researchers compared germ-free mice to mice with normal bacterial flora. Germ-free mice showed significantly higher levels of invariant natural killer T (iNKT) cells in their colons and lungs. “We made the serendipitous observation that these cells were dramatically enriched in the lung and colon in mice that lacked any microbes,” said the co-author Richard Blumberg, the chief of gastroenterology at Brigham and Woman’s Hospital in Boston. Body’s own production of elevated iNKT cells correlated with higher susceptibility to inflammatory bowel disease and allergic asthma in germ-free mice. Most strikingly, the study showed that exposure to these bacteria in late age did not lower the susceptibility to these immune diseases, indicating that the bacterial exposure needs to be early in life to boost the immune system. After all, broad-spectrum antibiotics for babies may not be such a good idea.

2- Giant chickens of Jurassic Park

Original article: Xu X. et al, Nature 484, 92 (2012)

Many of us undoubtedly learned a lot about dinosaurs from the famous Sci-fi movie Jurassic Park, but who would have imagined that some gigantic feathered dinosaurs would be running along with our favorite monster T-Rex? Paleontologists have recently made an incredible discovery in Liaoning Province of China. They found a set of perfectly preserved fossils that belong to a previously unknown species of dinosaurs. These 125-million-year-old feathered giant dinosaurs represent the largest feathered animal species ever lived on earth. The adult one is predicted to be at least 9 meters (30 feet) long with a weight of 1400 kg (~3000 pounds), which is approximately 40 times bigger than the Beipiaosaurus, largest known feathered dinosaur. New gigantic feathered dinosaurs are given a Chinese-Latin name Yutyrannus huali meaning a “beautiful feathered tyrant.” Simple filament like structures as well as the relatively small sizes of feathers seem more similar to feathers from a baby chick than the plumes of an adult bird, suggesting that Yutyrannus used feathers not for flying but for body temperature insulation, perhaps under the harsh climate conditions of that age. Paleontologists are really excited to see that how much more we have learned about dinosaurs over last 15 years and they predict that many different feathered meat-eating dinosaurs lived before and they are still yet to be discovered.

3- Stardust mystery revealed

Original article: Norris B.R.M. et al, Nature 484, 220 (2012)

Heavy elements are formed in the cores of stars and are crucial in formation of celestial structures like our earth. When an intermediate-mass star dies, it triggers a cosmic sandstorm that lasts thousands of years ejecting more than half of its mass into space. Our Sun is expected to go into a similar phase in around 5 billion years. Scientists observed these sandstorms for years but it was a mystery how these particles found could leave the vicinity of the stars and find their way into interstellar space. Computer simulations hinted that these sand-like particles could not be that small, otherwise they would be evaporated by the immense heat of the dying star. Scientists using the Very Large Telescope in Chile had a chance to explore these stars in a greater detail and discovered that the size of these particles is around a micrometer. This size might seem very small to us but for these particles, it is large enough to behave like mirrors for the light rays coming out of the star instead of absorbing them. Since light also behaves like a particle, the momentum transferred by this reflection helps particles to accelerate to the speeds like 10km/second. As the lead author of the study, Barnaby Norris from University of Sydney says: “The dust grains are like lots of little sails catching the wind, or in this case, starlight.” The material that comes out of the stars is recycled during the formation of new stellar objects like our old planet.

4- Babies understand more than we think

Original article: Bergelsona, E. & Swingley, D., P.N.A.S. 109, 3252 (2012)

Most babies do not say a meaningful word until they are a year old. It was not clear whether they knew the meaning of the words prior to the speaking age. It is easy to ask the question on whether the babies understand words but it is hard to scientifically measure it. The researchers from the University of Pennsylvania devised an ingenious experiment to test the hypothesis whether the 6-9 months babies understood the common words. During the experiment babies sat on their parents’ lap in front of a computer while some images of body parts or foods were shown on the screen. The parents were given instructions through headphones about what to say to the baby about the image on the screen. Babies were monitored by an eye-tracking device to measure their attention being directed to screen. The researchers designed a control environment by pairing a body part and a food item. For instance, if a banana and some hair were shown on the screen, the researchers measured the time that the baby fixated on the banana when the parent instructed the child to look at the banana versus when the parent instructed the baby to look at the hair. 33 infants of ages 6 to 9 months and 50 toddlers of ages 10 to 20 months were recruited for this study. The study convincingly showed that the babies fixated longer on an object when they were instructed to do so. Moreover, as the age of the babies increased the period of fixation stayed pretty much constant until 14 months, but jumped dramatically afterwards. The reason behind the jump in 14 months begs further research. Now, the researchers want also to test the vocabulary of the babies and whether the babies also understand the abstract concepts.

For a long time astronomers have talked about the nine planets orbiting the Sun. These nine heavenly bodies have always been more special than other objects orbiting the Sun, such as asteroids and comets. The nine planets are larger than others; you can see some of them in the sky even with the naked eye if you know where to look. In September 2003, astronomer Mike Brown of Caltech and his colleagues announced the discovery of a new object in the sky, then named 2003 UB313 Eris, which is 27% larger than Pluto. This made astronomers reconsider the definition of a planet, thereby making Pluto and Eris two of the new category of objects orbiting the Sun dubbed “dwarf planets.”

While astronomers are engaged in the debate on planet definitions, astrophysicists still have not agreed about how planets were created. In fact, the journal Science recently put the birth of planets on the list of the top 125 questions scientists will tackle in the next quarter century.1 The comment ended with: “Planetary systems around other stars should provide clues.”

The reason scientists are interested in extrasolar planets- planets orbiting other stars, or exoplanets in short- is not limited to their curiosity about how planets were created. The second major motive for exoplanet research is the attempt to detect another “habitable” planet. NASA’s Origins Program,2 for example, is attempting to answer the question, “Are there worlds like the Earth around nearby stars? If so, are they habitable, and is life as we know it present there?” This is one of the major questions the new field of astrobiology is striving to answer.

In this article, we give an overview of planets and exoplanets with an emphasis on the critical conditions for life on a planet.

Planets and Exoplanets

The International Astronomical Union’s 2006 definition of a planet states that a planet is a celestial body that (1) is in orbit around a star, (2) has sufficient mass so that it assumes a hydrostatic equilibrium (nearly round shape) but is not itself a star, and (3) has “cleared the neighborhood” around its orbit.

According to this definition, Pluto is indeed not a planet as its “moon” Charon is half the size of Pluto, whereas the moons of all other planets are much smaller than their respective parent planets. In addition, Pluto’s orbit is not as “clean” as the orbits of other planets.

Having introduced the new planet definition, we want to emphasize the first and foremost condition: a planet has to be in orbit around a star-not around the Sun. According to NASA Jet Propulsion Lab’s PlanetQuest website, as of August 2007, about 250 exoplanets in 99 planetary systems have been discovered. (The site exoplanets.org gives 228 planets around nearby stars.)

Discovery of solar planets is not too challenging: you take a clear picture of the same portion of the sky periodically, and compare the successive pictures. If you see an object that changes its position, then you can be sure that it is an object orbiting the Sun. Because stars are very far away compared to bodies orbiting the Sun, they seem stationary relative to us.

To give a sense of how far the stars are from us, think of the nearest star, Proxima Centauri, which is 4.3 light years away. One light year is the distance light travels in one year, which is 5.88 million million miles. If you fly a supersonic jet-a jet that can break the sound barrier (765 mph), such as the SR-713 or the MiG-25R, which can reach three times the speed of sound in the air-you would have to fly for about 1 million years nonstop to arrive at the nearest star. The most distant planet, Uranus, is about 0.002 million million miles away from the Sun, which is more than 12,000 times closer than Proxima Centauri-your trip to Uranus with a supersonic jet will take only about 80 years.

Exoplanets are as far away as stars. Therefore, it is impossible to detect them using the simple picture-the-sky method utilized for the solar planets. Every star with planets in its orbit is affected by the mass of the planets. This causes the star to sway back and forth. With extremely sensitive instruments measuring the Doppler shift in the frequency of light received from the star, the effect of the planet on the star can be detected.4 Another method is called astrometry: precise measurement of the positions of the stars relative to very distant stars, which appear stationary because they are far away. Small movements of the star because of the presence of planets can be detected.5

Direct optical detection of exoplanets is extremely hard, as they do not give off their own light. In the presence of the bright star, the planet becomes totally invisible. There are a few solutions. In the transit method, a planet blocks some of the star’s light as it transits past the star.6 Sensitive instruments can detect such small dips in the brightness of the stars. Also, interferometric detection7 can be used to detect the extremely weak light from the planet. Another optical detection method is called the “choronograph,” which is used to physically block the glare of the parent star, exposing the planet.

How are planets created?

The motion of a planet around the Sun can be described using two conservation laws-conservation of energy and conservation of angular momentum. Based on the understanding of orbital mechanics and the well-known laws of motion (first published in their entirety by Newton), it has become routine to place satellites in orbit around different planets to conduct various studies. Although science has been quite successful in describing planetary motion, we still do not know how planets were created. The conservation laws mentioned above do not determine the number, orbits, rotation directions, sizes, or type-rocky or gas giant-of planets. Initial conditions play a significant role; initial mass distribution around the star, the size of the particles orbiting the star during the early stages of the star’s life, and the initial orbits of these particles-when considered with the laws of motion, conservation laws, and the law of gravitational attraction-result in different planet-creation scenarios.

There are currently two main theories of planet creation, the gravitational instability and core accretion theories. In the gravitational instability theory, planets form during a rapid collapse of a dense cloud. In the core accretion theory, planets start as small rock-ice cores that grow as they gravitationally acquire additional mass.8 By detecting planets recently created around different stars, scientists hope to test these theories.

Search for life on exoplanets

Diverse life forms on the Earth are taken for granted. The average individual does not think much about the inner workings of life and the conditions that make life possible on the Earth.

Earth is a rocky planet that contains heavier elements, such as silicon, iron, and so on. We know that heavier elements were created during the supernova explosions,9 which comprised a few generations of stars, and therefore more than a few billion years. In a galaxy that is very young, one does not expect there will have been enough supernova explosions to produce heavy elements.

In an old galaxy, however, one does not expect to see radioactive elements. Thus, the planets that form in an old galaxy might be as dead as the moon because there will not be enough radioactive fuel. The Milky Way, our galaxy, is neither very young nor very old. Note that ages of galaxies and stars are in the order of billions of years-our sun is estimated to have been created about 4.6 billion years ago, and it is a middle–aged star.

In the Milky Way, our sun is placed at just the right spot, about halfway from the center.10 At the core of our galaxy, the density of stars is so high that they collide with each other. At the outer extremities, at the rim of the galaxy, the star density is too low to generate the heavier elements that make up planets as very few supernova explosions are expected.11

The orbits of all planets are elliptical, but very close to being circles. This is very significant for a planet if life is to prosper. Eccentricity is a measure of the elliptical shape of an orbit. A perfect circular orbit has an eccentricity of 0 (zero), and as the eccentricity comes closer to 1, the orbit becomes like a sausage. The earth’s orbit around the sun has an eccentricity of 0.067, very close to a perfect circle. If the eccentricity were to become 0.3, the average global temperature would become 73 F (23 C), compared with 58 F (14.5 C) on the Earth now, and, “some parts of the African, South American and Australian interiors heat up to 140 F (60 C)” when the Earth passes closest to the Sun,” according to Darren Williams and his colleagues of Pennsylvania State University.12 On an orbit with eccentricity of 0.4, the average temperature would increase to 86 F (30 C). Given the current scientific opinion on global warming and how catastrophic conditions could become because of a few degrees increase due to increasing amount of carbon dioxide in the atmosphere, you can imagine how unbearable the Earth would become for many complex life forms. Therefore, for a planet to bear life on its surface, its orbit must be at an optimum range of distances from the parent star, which is dubbed the “habitable zone.”

All planetary orbits around the Sun-not only that of the Earth-are nearly circular, and they do not cross each other’s orbits. If there were a number of planets with highly eccentric orbits around the Sun, some of them would cross the Earth’s orbit increasing the probability of a collision.

Obviously, a planet with life as we know it on Earth would need to be a rocky planet. In the solar system only four planets (Mercury, Venus, Earth, and Mars) are rocky planets; the other four (Jupiter, Saturn, Uranus, and Neptune) are gas giants.

The existence of gas giants, Jupiter being the largest of all, appears to be very important, too. Meteorite collision is a likely Doomsday scenario for the inhabitants of the Earth. In fact, meteorite collisions are cited as the main cause of the extinction of many species from the face of Earth in its several billion-year history.13 Jupiter is about 5au away from the Sun-1au is the mean Earth–Sun distance, nearly 150 million km-and as the most massive planet it plays a critical role in protecting the Earth from meteorites and comets.

In addition to all these astronomical conditions, the Earth has a magnetic belt that protects it from charged particles ejected from the Sun and other bodies. The Earth has an atmosphere,14 and the presence of water is absolutely critical for life.15

Of the almost three hundred exoplanets so far identified, most of them are gas giants as massive as Jupiter-more than 300 Earth masses. Therefore, scientists do not expect a glimpse of life on them. Recently, Christophe Lovis of the University of Geneva and his colleagues reported three low-mass planets orbiting the nearby star HD 69830, described as “hot-Neptunes” or “super-Earths”, as their masses are from 5–20 times the mass of the Earth. Scientists predict that two of these planets may be rocky planets based on theoretical calculations.16 For more conclusive results, however, telescopes with much higher resolutions are needed. Such telescopes are expected to be operational within a decade.

In conclusion, research interest in exoplanets originates from questions about the mechanism of planet creation, and the attempt to find planets where life can exist as we experience it on our blue planet. We do not know whether we will be able locate other worlds similar to the Earth with their own inhabitants. One thing we know, however, is that life is only possible through a great many critical conditions acting together in stars and planets as well as in cells and molecules. Life is very special indeed. Although the existence of other planetary systems suggests that our solar system is not as unique as once thought, with its “blue” planet -a planet that can support biological life-it still seems absolutely unique. Many scientists think, however, that with better tools and methods it is only a matter of time before we locate an Earth-like exoplanet. Time will prove or disprove their predictions.

Dr. Ertan Salik is an Assistant Prof. of Physics at California State Polytechnic Univ, Pomona. As well as teaching and conducting physics research Dr. Salik is currently involved in many education programs.

Notes

1. Science, Vol. 309, No. 5731, pp. 1–204 (2005).

2. NASA Origins program: http://origins.jpl.nasa.gov and http://origins.stsci.edu/

3. http://www.sr-71.org/ Accessed 2008-07-26.

4. Struve, Otto. “Proposal for a project of high-precision stellar radial velocity work”, The Observatory 72 (1952): 199–200, http://en.wikipedia.org/wiki/Doppler_spectroscopy Accessed 2008-07-26.

5. http://www.planetary.org/explore/topics/extrasolar_planets/extrasolar/astrometry.html Accessed 2008-07-26.

6. Charbonneau, D.; T. Brown; A. Burrows; G. Laughlin (2006). “When Extraslar Planets Transit Their Parent Stars”. Protostars and Planets V, University of Arizona Press.

7. Exoplanet detection using a nulling interferometer, Manuel P. Cagigal and Vidal F. Canales, Optics Express, Vol. 9, No. 1, 2 July 2001.

8. http://planetquest.jpl.nasa.gov/news/giantRockyCore.cfm Accessed 2008-07-26.

9. Gedik, Nuh. “Supernova Explosions and a Miracle of The Qur’an,” The Fountain, April-June 2006.

10. Weed, William Speed. “Circles of Life,” Discovery, November 2002.

11. See Charbonneau 2006.

12. Weed, 2002.

13. Gonullu, Omer Said. “The Message of Meteorites,” The Fountain, January–March 2005.

14. Cakmak, Osman. “A Journey in the Atmosphere,” The Fountain, January–March 2002.

15. Gedik, Nuh. “The Miracles of Water,” The Fountain, January–March 2005.

16. Lovis, Christophe et al. Nature, 441, 305–309 (18 May 2006).

…And We sent down Iron, in which is great might, as well as many benefits for mankind… (Hadid 57:25)

The above verse in the holy Qur’an uses the Arabic expression “anzalna”which means “sent down” for iron. But why? Early commentators understood this as having a metaphorical meaning to explain that iron has been sent to benefit people. But after understanding the nature of one of the most powerful explosions in the universe, you realize that the direct meaning “being physically sent down from the sky” miraculously points out to a very important scientific fact that was discovered only very recently. To understand and appreciate this miracle of the Qur’an, we will first talk about the life and death of stars and then come back to this verse to describe its relevance in detail.

Just like human beings, stars are also born, live, and die. One big difference is that they can live billions of years compared to the less than 100 years of human life. Also, for us, there is no way of knowing how long we will live or how we will die. But for a star, given its mass, you can predict its lifetime and the way it will die. Stars about the size of our sun live for a long time (a couple of billion years) and die gradually. Whereas massive stars with a mass of about 8 times the mass of our sun or more have short lifetimes (tens of million years) and die in a quick and incredibly violent explosion known as a supernova.

Supernova explosions are one of the most spectacular astronomical events observable by human beings. Normally, in a typical galaxy there are about 10 billion stars. A supernova happens to be one of these ordinary stars until it explodes. During the explosion, the amount of energy released by the supernova can exceed the energy of all the other stars combined in its galaxy! The power of this explosion is far too big even to imagine. The energy released is even greater than the total energy our sun will put out during its 10 billion year life!

The brightest supernova of modern times was an extragalactic supernova recorded in 1987. Since it was the first supernova in 1987, it was labeled as “1987A.” This is by far the best studied supernova of all times. In Fig. 1, the left panel shows the region of the sky two weeks after the supernova exploded. The supernova is still very bright. The right panel shows the same region before the explosion, with the arrow indicating the star undergoing the supernova explosion. This particular supernova was 160,000 light years away from us. This means that the actual explosion happened 160,000 years ago, but because it was so far from us, it took 160,000 years for the light rays from the explosion to reach us.

Fig 1. After and before images of the 1987A supernova. The left panel shows the region of the sky two weeks after the 1987A supernova exploded. The supernova is still very bright. The right panel shows the same region before the explosion and the arrow indicates the star undergoing the supernova explosion.

Since the supernova becomes extremely bright, it is even sometimes possible to see it with the naked eye in daytime. In fact, there are historical reports from ancient times concerning supernova explosions. On July 4th, 1054 A.D., Chinese astronomers noticed a “guest star,” which was visible in daylight to the naked eye for 23 days. Its remnant was discovered by the British amateur astronomer John Bevis in 1731. We now know that this bright “guest star” was a supernova. Its remnants, known as the Crab Nebula, are shown in the left panel of Fig. 2. This supernova is one of the very few that have been observed in our Milky Way galaxy. The last supernova to explode in our galaxy was in 1607 (see Fig. 2 right panel).

Supernova explosions are one of the most violent events that happen in the universe. They release an unbelievable amount of energy. But why would a star explode anyway? If it has so much energy still, why does it not remain shining peacefully as it does for most of its lifetime? To answer these questions, we need to remember how stars work.

Figure 2 Supernovae remnants. The left panel shows remnant of the supernova that exploded in 1054. It is about 6,500 light years from earth. It consists of diffuse interstellar gas and dust (nebula) spread in a circular region of a diameter of 6 light years.(Image Credit: FORS Team, 8.2-meter VLT, ESO ). The right panel shows remnants of the last supernova, which exploded in our galaxy in 1604. This combined image — from NASA’s Spitzer Space Telescope, Hubble Space Telescope, and e Chandra X-ray Observatory — unveils a bubble-shaped shroud of gas and dust that is 14 light-years wide and is expanding at 4 million miles per hour (2,000 kilometers per second). It is about 20,000 light years away from us.(Image and caption credit: NASA )/

Let us start by answering a more basic question: What is the energy source of stars? Stars produce their energy through a process called nuclear fusion. The idea is very simple; you fuse together light nuclei, like hydrogen, to produce heavier nuclei, like helium. In this process, the combined mass of low-mass nuclei is more than the resulting fused massive nucleus. This difference in the masses is converted to energy through the Einstein’s famous E=mc2 equation, where E is the energy released, m is the mass difference that is released in the reaction, and c is the speed of light.

But since the nuclei are positively charged, they repel each other, so there must be extremely high densities and temperatures to overcome this barrier. The most common form of fusion that takes place in stars is the fusion of four hydrogen nuclei to produce one helium nucleus. The temperature needs to be about 8 million C0 for this reaction to occur. It requires higher temperatures to fuse nuclei that are heavier than hydrogen. For example, fusing helium requires temperatures higher than 100 million C0.

During most of their lifetime, stars produce energy by fusing hydrogen into helium. After they run out of hydrogen, if the temperatures in their cores are high enough, they start to fuse helium nuclei into carbon and oxygen. And when they run out of helium, they then start to fuse carbon and oxygen. As mentioned above, fusing heavier elements requires extremely high temperatures and high pressures, so it can only happen for massive stars in the late stages of their lives where such conditions are met. For lighter stars like our sun, temperatures are not enough for this.

Even for the massive stars, fusion reactions cannot continue forever. The game of building heavier and heavier elements stops when iron is produced in the core. Iron is a very special element. It has the highest binding energy per nucleon. This makes it the most stable element. You actually lose energy when you fuse iron nuclei together rather than gain energy, so elements heavier than iron cannot be made during these cycles. At this stage of its life, the star looks like an onion, in the sense that it has a layered structure. At the core there is iron, surrounding this core there are layers of lighter elements in the order of their atomic weights, with hydrogen being at the outermost layer (see Fig. 3).

At this point in time, a very delicate balance that holds the star steady becomes unstable. Normally, the gravitational attraction tries to compress everything together. Therefore, the star has a tendency to collapse onto itself due to gravity. This is balanced by the outward radiation and thermal pressure that are generated by intense fusion reactions that are occurring in the core. But when the core turns into iron, fusion can no longer take place. That means there is no longer a supporting outward force that prevents the star from collapsing.

Figure 3 The onion skin model of a supernova. As it gets close to its death, a pre-supernova star has a layered structure that resembles an onion. Heavy elements produced by nuclear fusion inside the star are concentrated toward the center of the star. Iron, being the most stable element, sits at the core.

After the iron core gets to a certain size, this iron core suddenly collapses onto itself. This collapse happens so fast that it takes only a fraction of a second for the initially earth-sized core to shrink to a radius of 60 km. As the core collapses, the outer layers of the star start to collapse and rush in to fill the gap created by the collapsing core. At this point, another drastic event occurs. The iron core cannot compress forever. When the density in the core reaches the nuclear density, it rebounds. This time the core starts to move outward. But wait, the outer layers are still collapsing! When the collapsing envelope of the star meets with the rebounding core, one of the most powerful explosions in the universe occurs. This is known as a supernova explosion, which can be seen millions of light years away!

This gigantic collision ejects the outer layers of the star into the interstellar medium. As a result of the extreme conditions generated by this, the fusion of heavier elements (heavier even than iron) occurs. As the material from the exploding star collides with the interstellar gas and dust, a whole range of light emissions (from visible to X-ray) occurs. Colorful nebulae (as seen in Fig 2.) that will glow for thousands of years are thus generated.

One of the most important outcomes of supernova explosions is that heavy elements, including iron, are ejected into the interstellar medium. In fact, the only source of heavy elements is such events. All the heavy elements that are found in our solar system are made in one of these violent explosions. They cannot be made in our solar system, as they require extremely high temperatures. That means, the carbon that makes our cells, the hemoglobin that carries oxygen in our blood, and basically almost everything in our body are all made of elements produced in these explosions. We are, in the most literate sense, stardust. It is estimated that on average each carbon atom in our body went through four of these cycles in the past.

It is very clear that these explosions are important for the existence of life on earth. But, understanding the mechanism of these events was only possible in recent years.

It is extremely surprising to hear that iron and almost every other element in our body were made during one of these explosions. Even more astonishing is when we look at what the Holy Qur’an says about iron.

In the Holy Qur’an, there is a special chapter about iron, known as “Hadid” or “Iron”. The first thing that surprises you about this chapter is its chapter number: 57. The interesting thing about this is that it matches the atomic weight of one of the isotopes of iron. Iron can have stable isotopes with atomic weights of 54, 56, 57, and 58. The most common form of iron is the one with atomic weight 56 (56Fe).

The reason why this chapter is called “Iron” is the fact that in one verse of this chapter, the Holy Qur’an talks about iron. The second thing that is surprising is the verse number of this particular verse: 25 (or if you count the basmala, it becomes 26). This number (26) is the number of protons in an iron nucleus. And the third numerical code is the total number of verses in this chapter and that is equal to 30. This is equal to the number of neutrons in the most common form of iron nuclei (56Fe). Additional numerical codes can be found through a more detailed inspection of this Qur’anic chapter. No one knew anything about the iron nuclei in the 7th century when the Qur’an was revealed in its present form. And the chance of these numbers being purely coincidental is less than one in a thousand.

After studying these numerical codes, the content of the verse is even more interesting and closely related to our topic. In this verse, the Almighty says: …And We sent down Iron, in which is great might, as well as many benefits for mankind … (57:25). The expression “sent down” used for iron in this verse is the English translation of the Arabic word “anzalna”. This can either be understood as having a metaphorical meaning to explain that iron was given for the benefit of people. But, if the literal meaning, “being physically sent down from the sky,” is considered, we realize that this verse miraculously indicates the scientific fact that all the iron in our solar system came from the sky from supernova explosions.

Another interesting aspect is the fact that the verse says “…in which is great might …” The Arabic word “shaded” used to describe this can also be translated as “in which is great power” or as “in which is great violence”. If you assume this phrase is referring to iron, you can understand it to mean that iron has a great strength. Or a deeper meaning would be to consider the fact that iron nuclei is the most stable nuclei, i.e. the fact that it has the highest binding energy per nucleon. If you consider this phrase as referring to the act of sending down, in that case it reminds you of the great violence in supernova explosions.

In summary, supernova explosions are the violent deaths of massive stars. The course of events that leads to these gigantic explosions, as well as their far reaching consequences, is very interesting. They are the only source of iron and other heavy metals found in our solar system. They show the mercy of God, as life on earth without them would not be possible. At the same time, they can be thought of as an incredible show of divine power. As the Holy Qur’an says at the end of the verse that mentions iron:

Surely God is the All-Strong, the All-Glorious with irresistible might. (Hadid 57:25)

The Anglo-Australian Observatory (http://www.aao.gov.au/)

http://antwrp.gsfc.nasa.gov/apod/ap030914.html

http://www.nasa.gov/multimedia/imagegallery/image_feature_219.html

For more detailed discussion, see for example: Adam Burrows, Nature 403 (6771), 727 (2000).

http://chandra.harvard.edu/resources/illustrations/superPre.html

For example, according to numerological (abjad) calculations, the abjad of the word “Al-Hadeed” in Arabic, when the numerological values of its letters are added up is also 57 and numerological value of the word “Hadid” alone is 26. ( http://www.miraclesofthequran.com/scientific_30.html )