why does a star's life expectancy depend on its mass?

Answer 1

Because the bigger the star the faster it burns fuel, so the smaller the star the longer the life.

Answer 2

The more massive a star is the more gravity is crunching in on its core. And so fusion is much more intense in a massive star than in a less massive star. Therefore the massive star burn out its fuel much much faster. The most massive stars can run out of fuel after just a few million years while a tiny red dwarf can live on for a trillion years.

-edit-
There seem to be alot of misconceptions about stars here so I´ll explain a few things:

White dwarfs are not stars at all as they don´t "burn". There is no fusion going on anymore. They shine only through the release of gravitational energy. They are, infact, dead remnants of a dwarf/subdwarf star.

Red giants and red supergiants are dying stars that have evolved beyond the main sequence. All stars, including dwarf stars, enter this phase at the end of their lives.

Answer 3

Actually I'll use you as an example,....if I may and please dont be offended,....we all are born and we all die. So far we havent met anyone as old as humanity so we can assume we usually age the same way as others on average,....same way with stars,.......only stars live longer than us,.....they in fact can be observed to have a certain mass at a given time and therefore a certain gravitational influence,....but the same thing happens with you,.....the more you eat and drink and sleep and not excercise, the fatter you'll get and eventually you'll go supernova "in the human sense"......a heart attack.! or stroke or whatever,......well the same thign happens with a star but a star can shrink in size due to it's matter intake or lack of it or the addition of another similar body, therefore the star can gain size or shrink or whatever and can last infinitively long due to it's ability to eat "so to speak" other matter or other stars or gases or dust or just whatever happens along. so, lets say a star has a certain mass right now ansd then next week it has a smaller mass,....we then assume it is shrinking when in fact it might be getting ready to eat another mass that is approaching that we cannot observe from our viewpoint.......and the same goes for a massive star that is gaining in size,.....it might be ready to implode upon itself........our observations are at best "temporary" but at least it allows us to do enough math that we can make ceratin observations that help keep us intelligent enough to get more intelligent and then even more intelligent and then even so intelligent that we can obliterate ourselevs at a moments notice........does that make any sense to you at all?

Answer 4

It's rather strange, one would think that a massive star would last almost forever but, the more massive the star the shorter its life. White dwarf stars have just enough gravity to generate the compression needed for a nuclear reaction to happen. Then burn (fusion) their hydrogen so slowly that every white dwarf ever created is still burning. They may also be the last in the universe to die. The more massive a star the faster they burn (fusion) their hydrogen. Massive stars die in a nuclear reaction gone wild once they have burned (fusion) most of their hydrogen to other elements. Once they have fused a core of iron BOOM . . . . A very big BOOM.

D. bumstead

Answer 5

It seems backwards, but the more massive it is, the faster it burns up its fuel. Here's why:
If it has just barely enough fuel, only a tiny volume in the center is hot enough for fusion to take place so it takes forever for the hydrogen to work its way to the center and get used. If it has a lot more fuel, a much higher volume in the center is hot enough for fusion to take place so the hydrogen doesn't take so long to get used up.

Answer 6

Hi. A star need to burn (fuse hydrogen and other elements) to resist collapse. More mass, more gravity, more fuel needed to keep the gas from collapsing. Much shorter life.

Answer 7

Higher mass stars fuse their hydrogen at a much faster pace than low mass stars, therefore they don't stay on the 'main sequence' of stellar evolution as long.....where dwarf stars stay on the main sequence for billions of years, high mass stars only stay for millions of years...

Answer 8

It's opposite of those comments.

more mass=more fuel=fast burn (red giants)
less mass=less fuel=slow burn (dwarf stars)

Gravity pushes the 'burn' faster, and controls the relevant time factor. More mass = more gravity = a greater compression for the nuclear fusion = faster burning of fuel.

Answer 9

Because the mass of a star is mostly hydrogen (its fuel) and the more fuel the star has, the longer it can sustain the fusion reaction that drives it.

Doug

Answer 10

type in " the life cycle of a sun " into your search engine and read some of the articles ; you will be able to extract some great info from them.