0
Stellar Evolution
Stellar evolution is the life cycle of a star. Stars start out as clouds of gas and dust. The composition of the gas and dust will determine the stages that the star may go through.
500 Questions
Will the sun ever blow up?
Asked by Wiki User
In Brief:
In about 5 billion years, the Sun will dramatically expand and become a red giant, but it won't explode. It won't ever become a supernova.
An Explanation:
It is true that the Sun is very slowly expanding and getting brighter right now. The reason for this is that as it is burning hydrogen to helium in the core the amount of hydrogen there gradually decreases. In order to keep the energy generation rate the same, the temperature and density in the core must rise. This has the effect that the energy can flow to the surface a little faster and it puffs up the outer layers (as well slightly brightening the Sun). When the Sun runs out of hydrogen in its core completely (which won't be for another 5 billion years or so) nuclear reactions will stop there, but they will continue in a shell around the core. The core will contract (since it is not generating energy) and as it contracts it will heat up. Eventually it will get hot enough to start burning helium into carbon (a different nuclear reaction). While the core is contracting the hydrogen burning around it heats will heat up the outer layers which will expand, and while they do that they will cool. The Sun will then become what is called a Red Giant and its radius will be large enough to envelop the Earth! Eventually the Sun will also run out of helium in its core. When this happens the core will contract again, but it will never be able to get hot enough to start burning any other elements into anything else. There will still be nuclear reactions of helium and hydrogen in shells around the core though, and these will continue to heat up the outer layers and cause them to move outwards. The core will eventually turn into what we call a white dwarf star, which is an extremely small (roughly Earth sized) dense star. A white dwarf does not generate energy so it will just slowly cool as it shines. The outer layers of the Sun will turn into what we call a "planetary nebula" (although it has nothing to do with planets) and gradually drift out into the interstellar medium. Planetary nebulae are some of the most beautiful objects you can see in the night sky. So the Sun will never explode (even though more massive stars can and do). The difference is that the Sun isn't massive enough to ignite anything past helium in its core. More massive stars continue nuclear burning until they start making iron. This creates an unstable core which will then explode in a supernova explosion.
What element would more likely form during a nuclear fusion?
Asked by Wiki User
That depends on what element(s) are being fused.
- Fusing hydrogen produces helium
- Fusing helium produces carbon
After this the reactions get very complex, sometimes including catalytic fusion cycles of several elements. The end result of fusion is a nickel/iron alloy.
Is eta carinae bigger then vy canis majoris?
Asked by Wiki User
No, you don't have to confuse "more massive" with "bigger". The most massive star in the eta Carinae system may have 100 times the mass of the Sun and be dozens of times bigger than our star but it is far smaller than VY CMa.
VY CMa is a red supergiant that has swollen to an extremely large size due to shell burning of different layers on its last stages of life. VY CMa is a cool star. On the other hand eta Carinae is very hot and it is in a different evolutionary state.
It is so massive that it will never reach the red supergiant state because it is losing mass at a fast rate. Also the companion play a role and alters the evolution.
Eventually eta Car will become a WR star (a naked core) and explode as a supernova. The same fate is expected for VY CMa but since it has already become a rec supergiant it is very likely that it won't become a WR star. This shows that VY CMa is far less massive than eta Car.
What is the distance of the habitable zone from a red dwarf star?
Asked by Wiki User
About 0.5 AU, or about half the distance from Earth to the sun.
What is the process they generates energy into the core of the main sequence star?
Asked by Wiki User
Hydrogen fusion to make helium.
When a star runs out of hydrogen in its core to fuse, it begins collapsing, leaves the main sequence, then ignites helium fusion to make carbon, becoming a red giant.
How is the lifetime of a star comparable to stellar evolution?
Asked by Wiki User
Stellar evolution is the term for the changes a star undergoes during its lifetime.
Red giant is a luminous giant star of low or intermediate mass that is in a late phase of its evolution with nuclear fusion going on in a shell outside the core but not in the core itself?
Asked by Wiki User
Thermonuclear fusion is still going on in the core of a red giant, but it is a different type of thermonuclear fusion. The center of the core has reached high enough temperature and pressure that it can now burn helium, producing carbon.
3 4He --> 12C
The large amount of energy released by this type of fusion pushes the outer layers away, making a giant star. The expansion of volume of the surface layer causes it to cool, appearing red. Thus a red giant.
What is the difference between an average star and a massive star?
Asked by Wiki User
Massive stars are brighter, they burn up faster, and they die younger, usually in very energetic explosions.
Why does a star look smaller than another star but is bigger than the other star?
Asked by Wiki User
Normally you would observe the star's brightness, not its apparent diameter.The star's apparent brightness ("apparent magnitude") depends on its real brightness ("absolute magnitude"), and on the distance.
Similarly, the star's apparent angular diameter (which is VERY hard to measure) would depend on its actual diameter, and on the distance.
What is the difference between a white dwarf and a black hole?
Asked by Wiki User
A white dwarf is the final stage after the death of a star roughly the size of our sun. It is composed mostly of nickle and iron metal (the end products of nuclear fusion) and is initially very hot (i.e. "white"). Eventually it will cool off becoming a black dwarf and nearly impossible to detect.
A black hole is the final stage after the death of very massive stars. The mass of the star is so great that the force of gravity completely overwhelms any repulsion of the other three forces and quantum effects that prohibit matter from occupying the same place. The entire star's mass collapses into a single infinitesimally small point and an "event horizon" forms around this point where gravity is so strong that nothing including light can escape out of and anything falling through it will fall into that point with no chance of escape.
Stephen Hawking also hypothesized that the big bang also created many microscopic black holes that due to quantum effects radiate mass and energy faster and faster as they get smaller, until they suddenly explode destroying themselves. (Note: black holes created by the collapse of large dead stars cannot do this)
Where are the hottest brightest stars?
Asked by Wiki User
Hot bright stars do not live very long because they are big (have a lot of mass) and their core density means that they use up their fuel quickly and die young (in supernova explosions). This means you find the hottest brightest stars in star forming regions, stellar nurseries.
How long does the process of dying take for a star like our SUN?
Asked by Wiki User
That would depend on the size (mass) of the star. Please be more precise with your question for us to answer it.
Is Antares still alive?
Asked by Wiki User
At 883 times the size of our Sun, the supergiant star Antares is very much 'alive'.
What is a quark star?
Asked by Wiki User
A quark star is a hypothetical star that forms when a star that is too big to form a neutron star but less than a black hole collapses the neutrons slightly into their component particles.
Why is iron special in stellar evolution?
Asked by Wiki User
Energy is liberated through fusion reactions, producing heavier and heavier elements. There are two transient elements heavier than iron which are produced by standard stellar nucleosynthesis, but these are short lived and decay into lighter elements. Iron is the heaviest element forged in the heart of a star via standard stellar evolution.
All elements heavier than iron are the byproduct of a supernova, wherein atomic nuclei are smashed together with such force energy is consumed in the nuclear reaction. This is why there tends to be an abundance of stable isotopes as light as iron, but elements heavier than iron are much more rare. Lead is an exception to this general rule as it is the end product of a long radioisotope decay sequence.
When was The Combination of Stellar Influences created?
Asked by Wiki User
The Combination of Stellar Influences was created in 1940.
What is analyzed to determine the temperature of a star?
Asked by Wiki User
Two things.
First, the magnitude of a star; its brightness
Then, the magnitude is viewed through two different filters.
They are either U(ltraviolet) and B(lue) or B and V(isual), and belong to a photometric system called the UBV system.
From this, optical astronomers extrapolate the effective temperature of a star from its colour.
Is a red giant a main sequence star?
Asked by Wiki User
No, a red giant is a star that has just left the hydrogen burning main sequence and begun the next step, burning helium. As helium undergoes fusion at a much higher temperature than hydrogen undergoes fusion, the star expands dramatically and as it expands its outer layers cool to red heat.
What would stars be like if carbon had the smallest mass per nuclear particle?
Asked by Wiki User
Supernovae would be more common
