Why are main sequence stars near one solar mass considered by mnay astronomers to be the BEST candidate for...

Question

supporting planets that have given rise to intelligent lifeforms??

Please be specific if you can. Thank you.

Answer 1

Try to think about 'Anthropic principle' and search along that line.

Answer 2

The main ingredient for life is time. As Linda and Raymond said a star like the sun has a stable lifetime that is long enough for intelligent life to emerge. It took 4.5 billion years on earth to yield our intelligence. Had the sun been just 50% more massive it would have entered its red giant phase by now. And we would not be. So a star can´t be much more massive than the sun. And I too considered it unlikely that a very small low mass dwarf star could harbour planets with life capabilities. But then I read Isaac Asimovs bok "Nemesis" where he adresses the problems with red dwarfs in a quite ingenious and scientifically plausible way. He simply put the alien world in orbit around a gasgiant in the habitable zone. The moon is earthsized, has an atmosphere and its period around its parent planet gives it days and nights challenging the gravitational lock of the red dwarf. The huge magnetic field of the gasgiant would complement the magnetic field of the moon itself protecting it from the flares that a red dwarf might produce. Such a configuration may not be too likely and I don´t even think a planet has been found around a red dwarf but the sheer number of lower mass stars, the bulk of all stars in the universe, coupled with their extreme longevity, in the range of 100 billion years, means we shouldn´t count them all out as implausible for harbouring life.

Answer 3

There are a number of qualities these stars have that make them good candidates:
- they are stable (on the main sequence) for about 10 billion years, so there is enough time to form planets and for life to develop
- they are not likely to be highly variable (causing swings in temperature or radiation emission)
- the habitable zone of these stars is wide enough to allow one or more planets to orbit
- the habitable zone is far enough from the star so that a planet in that zone doesn't become tidally locked to the star
- stars that are Population I (like the sun) have enough metals (elements heavier than helium) to form good-sized rocky planets (if the star has a metal content similar to the sun, it means the nebula the star formed from had metals as well, and the planets would have incorporated them into their structure)

Answer 4

Because they have a long enough stable life on the main sequence to allow life (and intelligence) to develop.

Bigger stars burn their fuel too fast. The star would die before intelligence could develop.

Smaller stars were thought to have unstable surfaces (big flares = too much charged particles, ruining chances for complex life to develop). However, this view is slowly being challenged. However, being cooler, they have a much narrower "habitable zone", thereby reducing the probability of finding a planet at just the right distance for life.