How do scientists tell how many stars there are in a galaxy?

Question

If possible explain in detail please.

Answer 1

For the Milky Way galaxy, they can do a fairly reasonable census of the local region and extrapolate that to the rest of the galaxy. One aspect of this that has changed over time is that more powerful telescopes have revealed very large numbers of small faint stars - red and brown dwarfs. In nearby galaxies, they can see many of the brighter stars, and make assumptions about the total population based on the Milky Way.

In more distant galaxies, few, if any , stars can be seen, and they base their estimates on the total luminosity of the galaxy. You will often see a galaxy described as having the equivalent of so many billion suns. This is not an implied count of the stars, but a measure of how bright the galaxy is, using our sun as a familiar yardstick.

Answer 2

They do samples. It is just an estimate anyway. Pick one section of a galaxy and by looking at its density, estimate the number of stars. Do this for several sections and then extrapolate to the whole galaxy. You will note that the numbers given are not very precise - e.g.: 100 billion.

Answer 3

Scientist dont know for sure, they make an educated guess. Kinda like guessing how many grains of sand there are on a beach based on the size of the beach.

We can guess in our own galaxy based on: how many we can see, their distance, thier movement, and extrapolating this into a model of our galaxy. From there we can guess how many stars there are to 'fill in the gaps' that we cant see in our own galaxy. Assuming it is symetrical.

From their, we can see other galaxies and make an educated guess, based upon its size, movement, and shape.

Answer 4

They estimate the number based upon samples.... it's called statistical sampling.

http://en.wikipedia.org/wiki/Sampling_(statistics)

Basically, they select an area and count how many they believe to be within that area and then extrapolate the rest.

If you've ever seen on TV when they have huge crowds attending an open area gathering... they estimate the number of people in the crowd by taking a count of a sample area and estimating the remainder...

Answer 5

Look this is the simplest thing i could say.

They figure out the mass with some complex stuff, then using that number they figure out the number of stars.

Think of it this way. You have a jar of marbles which weighs five pounds. They are different sizes, but the average marble is 4 ounces. Do the math, and viola, an estimated 20 marbles.

Answer 6

They send out space census people who visit every star in the galaxy and collect information. I really don't know. Sorry....

Answer 7

They cannot count it......