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zed

How many stars like our Sun in the Milky Way?

2 posts in this topic

I know this is a (very) basic question but I can't find a satisfying answer after searching on Google.

I would like to know how many yellow dwarfs are in our galaxy.

I think 80% of the stars are red dwarfs in the Milky Way, so the yellow dwarfs must be below 20%. I wonder how many of that remaining 20% are non-yellow dwarfs (blue giants, hyper giants, etc)

This LA Times article says:

Many Earth-like planets orbit sun-like stars.. At least one in every four stars like the sun has planets about the size of Earth circling in very close orbits, according to the first direct measurement of the incidence of such planets.

That means that our galaxy alone, with its roughly 200 billion sun-like stars, has at least 46 billion Earth-size planets orbiting close to the stars, and perhaps billions more circling farther out in what scientists call the habitable zone

http://articles.latimes.com/2010/oct/29/science/la-sci-earthlike-planets-20101029

but I think that estimate is far from accurate, since there can't be 200 billion yellow dwarfs in the Milky way. At a total population of 400 billion stars, the yellow dwarfs can be at maximum below 80 billion.

Also I wonder how many yellow dwarfs can be in galaxies like Andromeda and in dwarf galaxies like SMC, LMC, Triangulum Galaxy and Canis Major Dwarf

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Basically it comes down to something called the IMF. Something astronomers haggle about a lot. The Initial Mass Function is a mathematical expression that gives you a guide for a large lump of gas how many stars it will make, and the distribution of their sizes.

It is now fairly well known that in general stars smaller than our sun are more common, and the high mass stars become much less common.

There are lots of models, but it usually ends up something like this

img51.gif

1 is our sun, on the log scale along the bottom, so you can see many more 0.1 mass stars, and very few 100 solar mass stars.

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