How many galaxies are their? Thats what I was wondering. Here is what i found out:
Your inquiry is definitely in the minds of many scientists who are trying to obtain a good estimate for the number of galaxies in the universe. The methods used to achieve such number varies, and therefore, the results would vary, too. Also, as new and improved technology becomes available, astronomers can detect fainter objects that were not seen before. These objects invest that have come into view will in turn change the estimated number of galaxies.
There are 42,000 square degrees over the full sky, and 60×60 = 3600 spots as big as the Hubble Deep Field per square degree index options , so the total galaxies is about 3600 x 42,000 x 200 = 3.6 x 4.2 x 2 billion or about 40 billion.
It has been said that counting the stars in the Universe is like trying to count the number of sand grains on a beach on Earth. We might do that by measuring the surface area of the beach, and determining the average depth of the sand layer. If we count the number option strategy of grains in a small representative volume of sand, by multiplication we can estimate the number of grains on the whole beach.
Both factors make stars appear dimmer. Observations at visible wavelengths are limited to a region of (more or less) 5000 light-years radius about the Sun, with a few windows in the intervening dust giving us glimpses of more distant areas (especially near the Galactic center). Our map of the Galaxy gets correspondingly more sketchy with distance. Guided somewhat by observations of other spiral galaxies, we think that the overall run of star density with radius is fairly well known. Getting a total stellar head count is more of a problem, because the stars that we can see to the greatest distances are also the rarest. Measurements of the relative numbers of stars with different absolute brightness (known in the trade as the luminosity function) shows that, for example, for every Sun-like star there are about 200 faint red M dwarfs. These are so faint that the closest, Proxima Centauri, despite being closer to the Sun than any other (known) star, takes very large binoculars or a telescope to find. So, to get the total stellar population in the Milky Way, we must take the number of luminous stars that we can see at large distances and assume that we know how many fainter stars go along with them. Recent numbers give about 400,000,000,000 (400 billion) stars, but a 50% error either way is quite plausible. Much of the interest in "brown dwarfs" stems from a similar issue---a huge number of brown dwarfs would not change how bright the Galaxy appears (at visible wavelengths), but would change its total mass quite substantially. Oddly enough, within a particular region, we probably know the total mass and luminosity rather more accurately than we do just how many stars are producing that light (since the most common stars are by far the dimmest).
