Stars are massive celestial bodies composed primarily of hydrogen and helium. Twinkle, twinkle, little star may put a baby to sleep, but the phrases aren’t precisely accurate beyond the boundaries of Earth. A more accurate, if less calming, version may be: Emit, emit, massive ball of gas.
The brilliance of a star is also affected by its proximity to us. The further away an object is, the darker it appears. As a result, if two stars have the same brightness but one is closer, the closer star will appear brighter than the more distant star – even though they are both equally bright!
To find more about how stars shine in the sky, keep on reading.
Why Are Stars So Bright?
Some stars shine more brightly than others. Their brightness is a factor of how much energy they put out–known as luminosity–and how far away from Earth they are. Color can also vary from star to star because their temperatures are not all the same. Hot stars appear white or blue, whereas cooler stars appear to have orange or red hues.
How Is A Star Formed?
When atoms of light elements are crushed under enough pressure for their nuclei to fuse, a star is formed. All stars are the consequence of a balance of forces: gravity compresses interstellar gas atoms until fusion reactions begin.
When the fusion processes start, they create outward pressure. The star remains stable as long as the inward force of gravity and the outward force generated by the fusion reactions are equal.
Life Cycle Of A Stars
A star’s life cycle lasts billions of years. In general, the larger the star, the shorter its life period.
Birth occurs within nebulae, which are hydrogen-based dust clouds. Gravity forces pockets of dense matter within the nebula to collapse under their own weight over thousands of years. A protostar is a contracting mass of gas that symbolises the early phase of a star. Protostars can be difficult to spot because the dust in the nebulae obscures them.
Because of the conservation of angular momentum, as a protostar shrinks, it spins faster—the same principle that causes a spinning ice skater to accelerate as she draws in her arms. Rising pressure causes rising temperatures, and a star enters the comparatively brief Tauri phase during this time.
When the core temperature reaches roughly 27 million degrees Fahrenheit (15 million degrees Celsius), nuclear fusion begins, igniting the core and kicking off the next—and longest—stage of a star’s life, known as the main sequence.
The majority of stars in our galaxy, including the sun, are classified as main sequence stars. They are in a stable nuclear fusion state, fusing hydrogen to helium and emitting x-rays. This process generates a tremendous quantity of energy, which keeps the star hot and shining brilliantly.
How Does A Star Turn Into A Blackhole?
A black hole is a region in space where the pulling force of gravity is so strong that light is not able to escape. The strong gravity occurs because matter has been pressed into a tiny space. This compression can take place at the end of a star’s life. Some black holes are a result of dying stars.
Stellar black holes form when the center of a very massive star collapses in upon itself. This collapse also causes a supernova, or an exploding star, that blasts part of the star into space. Scientists think supermassive black holes formed at the same time as the galaxy they are in.
Why Do The Stars Collapse And Explode?
The larger a star, in general, the shorter its life, yet all except the most massive stars live for billions of years. Nuclear reactions stop after a star has fused all of the hydrogen in its core. When the core is deprived of the energy required to sustain it, it begins to collapse in on itself and gets much hotter.
Because hydrogen is still available beyond the core, hydrogen fusion continues in a shell around it. The expanding hot core pushes the star’s outer layers outward, forcing them to expand and cool, changing the star into a red giant.
If the star is sufficiently massive, the collapsing core may become hot enough to support more exotic nuclear reactions that consume helium and produce a variety of heavier elements up to iron. However, such reactions offer only a temporary reprieve.
Gradually, the star’s internal nuclear fires become increasingly unstable – sometimes burning furiously, other times dying down. These variations cause the star to pulsate and throw off its outer layers, enshrouding itself in a cocoon of gas and dust. What happens next depends on the size of the core.
What Is A Supernova?
Main sequence stars with masses greater than eight solar masses are doomed to perish in a massive explosion known as a supernova. A supernova is more than just a larger nova. Only the star’s surface erupts as a nova. The core of a star collapses and then explodes in a supernova. A complex series of nuclear events in large stars results in the synthesis of iron in the core.
After obtaining iron, the star has extracted all of the energy it can from nuclear fusion – fusion reactions that make atoms heavier than iron consume energy rather than producing it. The star can no longer maintain its own mass, and the iron core collapses.
The core shrinks from around 5000 miles across to just a dozen in a matter of seconds, while the temperature rises by 100 billion degrees or more. The star’s outer layers initially collapse with the core but bounce with the massive release of energy and are hurled forcefully outward.
Supernovae produce an enormous amount of energy. A supernova can outshine an entire galaxy for days or weeks.
Conclusion
Stars are astronomical bodies made of many elements like carbon, nitrogen, and oxygen, that shine brightly. Stars are born within clouds of dust and scattered throughout most galaxies.
