Exploring The Southern Stars - Full Documentary
"Billions and billions" of stars in a galaxy (after a quote often mistakenly attributed to Carl Sagan) is how many people imagine the number of stars you would find in one. Is there any way to know the answer for sure?
"It's a surprisingly difficul... More
Exploring The Southern Stars - Full mentary
"Billions and billions" of stars galaxy (after a quote often mistakenly ibuted to Carl Sagan) is how many people ine the number of stars you would find in Is there any way to know the answer for ?
"It's a surprisingly difficult tion to answer. You can't just sit around count stars, generally, in a galaxy," David Kornreich, an assistant professor thaca College in New York State. He was founder of the "Ask An Astronomer" ice at Cornell University.
Even in the omeda Galaxy — which is bright, large and tively close by Earth, at 2.3 million t-years away — only the largest stars and w variable stars (notably Cepheid ables) are bright enough to shine in scopes from that distance. A sun-size would be too difficult for us to see. So onomers estimate, using some of the niques below.
The primary way astronomers mate stars in a galaxy is by determining galaxy's mass. The mass is estimated by ing at how the galaxy rotates, as well as spectrum using spectroscopy.
All xies are moving away from each other, and r light is shifted to the red end of the trum because this stretches out the t's wavelengths. This is called shift." In a rotating galaxy, however, e will be a portion that is more eshifted" because that portion is htly moving toward Earth. Astronomers also know what the inclination or ntation of the galaxy is before making an mate, which is sometimes simply an cated guess," Kornreich said.
A nique called "long-slit spectroscopy" is for performing this type of work. Here, longated object such as a galaxy is ed through an elongated slit, and the t is refracted using a device such as a m. This breaks out the colors of the s into the colors of the rainbow.
Some hose colors will be missing, displaying same "patterns" of missing portions as ain elements of the periodic table. This astronomers figure out what elements are he stars. Each type of star has a unique ical fingerprint that would show up in scopes. (This is the basis of the OBAFGKM ence astronomers use to distinguish een types of stars.)
Any kind of scope can do this sort of spectroscopy . Kornreich often uses the 200-inch scope at the Palomar Observatory at the fornia Institute of Technology, but he d that almost any telescope of sufficient would be adequate.
The ideal would be g a telescope in orbit because scattering rs in Earth's atmosphere from light ution and also from natural events — even thing as simple as a sunset. The Hubble e Telescope is one observatory known for sort of work, Kornreich added.
The er of stars is approximately …
So is e any way to figure out how many stars for sure? In the end, it comes down to an mate. In one calculation, the Milky Way a mass of about 100 billion solar masses, t is easiest to translate that to 100 ion stars. This accounts for the stars would be bigger or smaller than our sun, averages them out. Other mass estimates g the number up to 400 billion.
The at, Kornreich said, is that these numbers approximations. More advanced models can the approximation more accurate, but it d be very difficult to count the stars by one and tell you for sure how many are he galaxy.Less