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Nuclear fusion
- Stars are the source of almost all of the light our eyes see in the sky. Nuclear fusion is what makes a star what it is: the creation of new atomic nuclei within the star’s core. Many of stars’ properties — how long they live, what color they appear, how they die — are largely determined by how massive they are.
www.cfa.harvard.edu/research/topic/stellar-structure-and-evolutionStellar Structure and Evolution | Center for Astrophysics ...
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Stars are giant balls of hot gas – mostly hydrogen, with some helium and small amounts of other elements. Every star has its own life cycle, ranging from a few million to trillions of years, and its properties change as it ages.
A star is a luminous spheroid of plasma held together by self-gravity. [1] The nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night; their immense distances from Earth make them appear as fixed points of light.
- Giant Gas Cloud/Nebula
- Protostar
- T-Tauri Phase
- Main Sequence
- Red Giant
- White Dwarf
- Black Dwarf
- Red Supergiant
- Supernova
- Neutron Star Or Black Hole
At the first stage of their lives, stars are formed by the gravitational collapse of giant clouds of dust and gas called Nebulae. This stage is the start of their life cycle.
A protostar is the result of the gravitational collapse of a nebula. It is the formative phase of a star. During this phase, the infant star strives to gain equilibrium between its internal forces and gravity. A Protostar starts very vastly. It can be billions of kilometers in diameter. It usually lasts for 100,000 years. During this period, the pr...
Before fusion begins, the protostar goes through a period called the T-Tauri phase. At this stage, the core temperatures are still too low for hydrogen fusion, so all the star energy comes from the gravitational forceonly. The star at this point is about the same size as a low or medium mass star. However, it is much brighter. This period can last ...
The Main Sequence signifies the portion of a star’s life where its core is capable of hydrogen fusion. 90% of a star’s life is spent in this stage. The stars in the Main Sequence are of many different masses, colors, and brightness. The amount of time a star spends on the Main Sequence depends directly upon its mass. average stars like the Sun stay...
When a star has fused all the hydrogen in its core, its nuclear radiation output ceases. As a result, the star once again starts collapsing due to gravity. The energy generated by this collapse heats the core enough that the hydrogen in the surrounding stellar atmosphere can be burnt. This process causes the star’s outer layers to expand and cool d...
Once the star’s outer layers are shed, only a tiny core comprising primarily carbon and oxygen remains. The star is called a White Dwarf. Here, the mass of an entire stellar core is condensed into a body roughly the size of the Earth. Such a small size is possible due to the pressure exerted by the fast-moving electrons. This fate is only for those...
Black dwarfs are the final stage in the life of a low to medium mass star. They are the remnants of white dwarfs, formed due to the gradual cooling and dimming as they burn their remaining fuel. Eventually, they will exhaust their fuel and keep dimming until they are no longer visible to us. This process takes such a long time that no black dwarfs ...
For stars with a mass 8-9 times that of the Sun, the core temperatures become so high that nuclear fusion can occur even after the helium is exhausted. They can swell up to truly spectacular sizes; for example, Betelgeuse, a red supergiant and the tenth brightest star in the sky, is so massive that if it were in the Sun’s place, it would stretch ti...
The moment the core of a supergiant star turns to iron, it has reached the end of its life. The star collapses instantly under the enormous gravity exerted on its heavy iron core. The core shrinks from around 5000 miles across to just a couple dozen in a matter of seconds, and the temperatures can reach 100 billion K. This collapse triggers an incr...
After a supernova explosion, all that remains of the star is its core. What happens to this core depends on its mass. a) Neutron Star:If the collapsing core is of 1.4-3 solar masses, it forms a Neutron Star. A neutron star is a highly dense, heavy, and trim body comprised of neutrally charged neutrons. The force of gravity on the collapsing core is...
There are seven main types of stars. In order of decreasing temperature, O, B, A, F, G, K, and M. O and B are uncommon, very hot and bright. M stars are more common, cooler, and dim. The video below presents a helpful overview of the types of stars in the Universe.
Oct 13, 2023 · The birth of a star is a captivating balance of gas, dust and energy. The transition from quiet cosmic particles to radiant celestial bodies is a process as intricate as it is magnificent. Read on to explore the steps and stages of star formation, illuminating the evolution that lights up the cosmos.
Oct 3, 2024 · What is a star? A star is any massive self-luminous celestial body of gasthat shines by radiationderived from its internal energy sources. Of the tens of billions of trillions of stars in the observable universe, only a very small percentage are visible to the naked eye. Why do stars twinkle?
Jul 15, 2014 · A star is a luminous ball of gas, mostly hydrogen and helium, held together by its own gravity. Nuclear fusion reactions in its core support the star against gravity and produce photons and heat, as well as small amounts of heavier elements. The Sun is the closest star to Earth.
