Stars seem pretty permanent don’t they? One generation goes and another arrives and there they still are, exactly as described before for hundreds of years. Yet all this is merely an illusion of permanence that doesn’t exist. The truth is that stars have lifetimes just as humans do but their lifetimes are measured in millions and billions and trillions of years instead of mere decades.
The situation can be illustrated by comparing human lifespan to that of Mayflies that are born and don’t even last a day before they are dead. If they could reason, we might appear like stars never changing. One generation of flies would tell the others that we had been present at the river-bank house for 365 of their generations which to us would have been merely a year. Same with stars, they look long-lived because we are short-lived but they did have their birth, do experience middle age, then old age and death just as we humans do. The difference is that our aging and deaths are based on the deterioration of our cellular activities while stars age in accordance with how massive they are and the effect it has on their nuclear-fusing cores. Notice in the following chart how mass is correlated to stellar lifespan:
Star mass Time (years) Spectral type
60 (solar masses) 3 million O3
30 (solar masses) 11 million O7
10 (solar masses) 32 million B4
3 (solar masses) 370 million A5
1.5 (solar masses) 3 billion F5
1 (solar masses) 10 billion G2 (Sun)
0.1 (solar masses) 1000's billions M7
When a star is considered dead:
A star is considered dead once it ceases to fuse elements into other elements in its core or shells surrounding the core. Such stars are called Neutron stars, white Dwarfs, black dwarfs, or black holes.
Just as we change in appearance so do they. Some become bloated into red giants and then finally become white dwarfs and eventually black dwarfs. Others blow up and finally become neutron stars or black holes.
Stars that resemble our sun aren’t as long lived as are red dwarfs which make up approx 76 percent of the stars. That’s because being less massive, red dwarfs are using up their fuel at a far lower rate. The faster the rate the so the shorter the star’s lifespan. The denser the star is, the faster it consumes the elements in its core and the more violent are its stages in like. Some go what is called nova, super nova and still others hypernova after expanding their outer layers to vast proportions called giant supergiant and hypergiant stages. Red dwarfs never experience such stages and remain behind as other stars are being born and dying.
Sun-like stars have a predicted age of ten billion years.
Reference www.physicsforums.com/threads/giant-stars.565634/
w.eg.bucknell.edu/physics/astronomy/as102-spr00/web_pages/web8.html
www.physicsforums.com/threads/giant-stars.565634/
Dead Stars
curious.astro.cornell.edu/physics/80-the-universe/stars-and-star-clusters/stellar-remnants/364-if-a-white-dwarf-is-a-dead-star-why-is-it-so-hot-intermediate
http://writerdreams.freeforums.net
The situation can be illustrated by comparing human lifespan to that of Mayflies that are born and don’t even last a day before they are dead. If they could reason, we might appear like stars never changing. One generation of flies would tell the others that we had been present at the river-bank house for 365 of their generations which to us would have been merely a year. Same with stars, they look long-lived because we are short-lived but they did have their birth, do experience middle age, then old age and death just as we humans do. The difference is that our aging and deaths are based on the deterioration of our cellular activities while stars age in accordance with how massive they are and the effect it has on their nuclear-fusing cores. Notice in the following chart how mass is correlated to stellar lifespan:
Star mass Time (years) Spectral type
60 (solar masses) 3 million O3
30 (solar masses) 11 million O7
10 (solar masses) 32 million B4
3 (solar masses) 370 million A5
1.5 (solar masses) 3 billion F5
1 (solar masses) 10 billion G2 (Sun)
0.1 (solar masses) 1000's billions M7
When a star is considered dead:
A star is considered dead once it ceases to fuse elements into other elements in its core or shells surrounding the core. Such stars are called Neutron stars, white Dwarfs, black dwarfs, or black holes.
Just as we change in appearance so do they. Some become bloated into red giants and then finally become white dwarfs and eventually black dwarfs. Others blow up and finally become neutron stars or black holes.
Stars that resemble our sun aren’t as long lived as are red dwarfs which make up approx 76 percent of the stars. That’s because being less massive, red dwarfs are using up their fuel at a far lower rate. The faster the rate the so the shorter the star’s lifespan. The denser the star is, the faster it consumes the elements in its core and the more violent are its stages in like. Some go what is called nova, super nova and still others hypernova after expanding their outer layers to vast proportions called giant supergiant and hypergiant stages. Red dwarfs never experience such stages and remain behind as other stars are being born and dying.
Sun-like stars have a predicted age of ten billion years.
Reference www.physicsforums.com/threads/giant-stars.565634/
w.eg.bucknell.edu/physics/astronomy/as102-spr00/web_pages/web8.html
www.physicsforums.com/threads/giant-stars.565634/
Dead Stars
curious.astro.cornell.edu/physics/80-the-universe/stars-and-star-clusters/stellar-remnants/364-if-a-white-dwarf-is-a-dead-star-why-is-it-so-hot-intermediate
http://writerdreams.freeforums.net
