# How many galaxies have been discovered?

I know Andromeda is our nearest galaxy. But how many known galaxies have been discovered and what are they?

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First, the nearest galaxy to ours is not Andromeda, according to the NASA based page "The Nearest Galaxies", it was until recently considered to be the Canis Major Dwarf Galaxy at approximately 42,000 light years away. However, recently, there is suggestion that the closer Omega Centauri Globular Cluster may be a disrupted dwarf galaxy (Another source).

Now, in answer to your other query of how many galaxies there are - there is a global project called Galaxy Zoo which is attempting to catalogue and classify all observed galaxies, so far, according to the Galaxy Zoo for astronomers page, thus far they have

• the entire Sloan Digital Sky Survey spectroscopic sample and all existing Hubble Space Telescope surveys (around 1.5 million galaxies in total).

Pictured: The Hubble Ultra-Deep Field which contains over 10,000 objects, the majority of which are galaxies. The image is only a bit over 3 arcminutes across--a tiny sliver of the sky.

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Wow 1.5 million is a huge number to be listed. Thanks for the info, I had no idea we had discovered so many. –  Unicorn Sep 25 '13 at 7:00
@Unicorn - it is remarkable isn't it and that is only a tiny fraction of the total amount believed to be out there. Digging around they have accessible data on that site. –  user8 Sep 25 '13 at 7:01
If you want to know the number of spectroscopically confirmed galaxies then the number given by UV-D is roughly correct.
The case I know is the Sloan Digital Sky Survey 3 (SDSS3): they observed about a third of the sky using five different filters between optical and near infrared. Of all the objects detected 208,478,448 are galaxies. And of those 1.5 to 2 millions will have the spectrum measured by mid next year. More info here