Physical Cosmology

What kinds of stars fill our galaxy?
Answered by Dr. Evgenya Shkolnik
  • Dr. Evgenya Shkolnik

    Dr. Evgenya Shkolnik

  1. Dr. Evgenya Shkolnik Astronomer, Lowell Observatory


    Our galaxy is made up of over 100 billion stars, which is quite remarkable. And that's just in our one Milky Way galaxy, and the stars range from 100 solar masses to a tenth of a solar mass. A solar mass is the mass of our sun, by which we define everything because it's the star we know the most about. It's the closest star and gives off the most light. We can actually resolve it on the sky. We can see the full disk. All other stars are just point sources on the sky because they're so far away, they're just little dots. We know the most about the sun, so everything is done related to the sun. Chemical compositions of stars are relative to the sun, and their ages are relative to the sun sometimes. 

    We have a wide range of possible masses for stars. Now, the sun, however, is not the most common type of star. It's an average-sized star -- it's in the middle of the range, somewhere between 100 and a tenth of a solar mass -- but 75 percent of the stars in our galaxy are what we call M dwarfs. These are low-mass stars that have masses between a tenth to a half of a solar mass star. And they certainly dominate the galaxy.

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