I have data that contains galactic latitude and longitude of stars. I have to determine all the stars that are within our milky way. How do I find it?

  • $\begingroup$ Do you also have distance-from-Earth data for all of these stars? If so, and the distance is less than a few dozen thousand light-years, I suspect the answer is "all of them are in the Milky Way" $\endgroup$
    – notovny
    Commented May 16, 2019 at 15:31
  • 1
    $\begingroup$ Milky way can mean two things. One is the name of our galaxy, the second is a band of light in the sky. By "within our milky way" do you mean "in our galaxy" or "positioned in the band of light." $\endgroup$
    – James K
    Commented May 16, 2019 at 20:39

1 Answer 1


Stars beyond our own galaxy and its immediate neighbors are indistinct without a large telescope, so I assume the question is about the band across the sky, rich with faint stars.

The Milky Way's boundary is fuzzy, so its extent is expressed in terms of isophotes: lines of constant brightness per unit solid angle (e.g. square degree). It is wider near the central bulge (galactic longitudes around 0° or 360°) than away from it (around 180°). Most stars within galactic latitudes ±10° are in the Milky Way; most outside ±15° are not. At galactic latitudes in between, galactic longitude and the choice of isophote determine whether a star is in or out.


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