While the Earth is a small component of the vast Solar System, the latter in itself is a small component of a larger entity referred to as the Milky Way, which is a galaxy. Other than our solar system, the Milky Way has billions of stars in it; some of which are bigger than the Sun. Having said that, we are yet to find out the size of the Universe, and therefore, we still refer to it as 'infinite'.
Considering that the Universe contains all the galaxies and inter-galactic space that exists, it has to be very vast in nature. But is it possible to find out the expanse of Universe based on the number of galaxies out there? Now that's a question which has left some of the eminent astronomers of the world baffled, as we are far from coming up with a concrete answer for either of the two questions.
How Many Galaxies are There in Our Universe?
It is virtually impossible to find out the exact number, considering that we are yet to know the expanse of the Universe in itself. Whatever numbers that are being put forth by various astronomical bodies are mere estimates based on the data compiled by some technologically advanced instruments used for this process. As we said earlier, scientists estimate that there are hundreds of billions of galaxies out there. Some of these estimates also put the number somewhere between 100 to 200 billion as a whole. The pictures captured by the Hubble Space Telescope back in 1999 suggested that there are as many as 125 billion galaxies in the Universe.
We may boast of using all the high-tech equipment available in the field of astronomy today, but we are only well-versed with a fraction of the Universe. Over the last few years, we have achieved quite a few technological breakthroughs in this field, but then, we can't ignore the fact that the Universe is expanding and so is the number of galaxies in it. In order to count all the galaxies, we will either have to go back in time or explore all the corners of the Universe―both are virtually impossible as of today. That again makes us dependent on estimates to find out how many galaxies exist.
In order to get an estimate of the same, astronomers first count the galaxies that can be seen in a particular section of the Universe, and then use this number to find out the total number of galaxies that probably exist out there.
What about the Observable Universe?
In star astronomy, the term observable Universe is used for the part of the Universe―along with all the galaxies and other matter in it, which can be seen from the Earth at a given point of time. Irrespective of what the shape of actual Universe is, the observable Universe is always spherical in shape with its center at the place from where the observations are recorded. So, every point of the Universe has an observable Universe of its own and the chances of same overlapping with that of the Earth cannot be ruled out. In the Earth's observable Universe alone, there are as many as 170 billion galaxies.
At the end of the day, it is virtually impossible to ascertain the number of galaxies in the Universe as of today. In future, however, things may change and we may (or may not) come across some method to answer this intricate question with an exact figure, instead of going with the estimates.
We are yet to go a long way in the field of space exploration, and as we make it to each milestone, more and more amazing facts about the Universe will come to light. One such milestone will be the launch of James Webb Space Telescope (JWST)―a planned infrared space observatory, as a part of the international collaboration between the National Aeronautics and Space Administration (NASA), European Space Agency (ESA), and the Canadian Space Agency (CSA) in 2013.