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.
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.
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.
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.”