Kapteyn Universe
Herschel and later Kapteyn counted stars in different directions
to determine the
shape of the Milky Way galaxy and our position in the Milky Way.
To understand how star
counting works, consider
So, the three-dimensional distribution of stars around us, that is,
whether they are distributed in a thin shell or in a
spherical distribution or in a disk or a football shaped region or whatever,
can also be deduced from star counting and measuring the brightnesses of
the stars.
Herschel and Kapteyn performed the star counting and star brightness exercise
and found that the Milky Way was a flattened distribution of
stars, around 33,000 light years x 6,500 light years and that the Sun was
around 2,000 light years from the center of the galaxy. Today, we believe that
the Milky Way is at least 80,000 light years x 2,000 light years in size and
that the Sun is 25,000 light years from the center of the galaxy!!
Herschel and
Kapteyn deduced that the Milky Way was not nearly as flat as we know it to
be and that we were very nearly at its center.
What is the meaning of this?
Are we near the center of the Milky Way galaxy?
Lecture
1
Lecture
2