View Full Version : how many galaxies are there?

2003-Nov-27, 01:17 AM
I've asked many sources this question and the most common answer seems to be at least 300,000,000 galaxies.I,d like to get more input from as many sources as possible.Yhe deep field image of the Tadpole galaxy would suggest this number .A fairly recent German super-computer simulation puts the number as high as half a trillion.Just the size of ours is pretty much unfathomable.I,d appreciate any input!

Michael Jensen

2003-Nov-27, 02:33 AM
A lot......Or Infintie.....

2003-Nov-27, 04:13 AM
:o I will bet there are even more than that


Dave Mitsky
2003-Nov-27, 07:04 AM
The figure that is usually touted is 50 to 100 billion galaxies. However, there is the general impression that most of these galaxies are the same size as the Milky Way. This is not correct. Just as most stars are small red dwarfs, most galaxies are dwarf galaxies. The Milky Way is a much larger and massive galaxy than the norm.

Dave Mitsky

2003-Nov-27, 02:02 PM
I remember the popular press releasing the number of stars in the universe (I don't have an official source, sadly). This was within the last couple of months.

70,000 million million million, I think

70 000 000 000 000 000 000 000
CNN source (http://edition.cnn.com/2003/TECH/space/07/22/stars.survey/)

Certainly enough there to share!

2003-Nov-27, 02:55 PM
The number of galaxies is probably constrained to less than infinite but is probably unknowable since an unknown portion of the universe is not detectable. The theorists may be able to put an upper bound on the amount of mass present at the big bang, then postulate an average mass for a "standard galaxy" and with some assumptions about the portion of mass unincorporated in galaxies and further assumptions about the transferability of mass between observable and dark forms, make a pretty good guess at how many galaxies there may be. I doubt that such knowledge will be useful.

The number of galaxies in the observable universe can be bracketed with safer assumptions based on large scale homogeneity, actual limits of observability (farthest points from which light has had time to reach us), caveated by our instruments limitations, and the observed number of galaxies per solid angle.

I doubt we'll ever be sure how many there really are, but there are more than we, including all our descendants, can ever visit, or, even if we did, know that to have been the case.

2003-Nov-27, 11:23 PM
I claim 5 billion billion billion in the name of me.

2003-Nov-29, 06:01 PM
that would be really endless travel, no matter how far our future is, how hypermodern rocket we have, star trek etcetera, we are very little organic life, like a one sandstone of the beachs from whole earth. That fancisate me very much that universe is very mega-huge with thousand billion galaxies, it's just endless, infinite and unreachable.

2003-Nov-30, 01:25 AM
Every one of the post-replies could be somewhere close to correct. How could we possibly know, when we are still finding more and more objects further and further away. As we get better telescopes and computer technology; our knowledge of what we can "see" continues to expand, so will the estimates of numbers of galaxies (as well as planets of any kind).[COLOR=green]

2005-Nov-29, 03:12 PM
Has there been any movement in this field of late? Galactic Estimation? Surely the fact is that whatever number there actually are, to us, marooned as we are in an outer-ish arm of the Milky Way, its as good as infinite.

I would be absolutely amazed if we ever visited another galaxy besides our own. Distances involved are utterly incomprehensible.

2005-Nov-29, 04:00 PM
I would be absolutely amazed if we ever visited another galaxy besides our own. Distances involved are utterly incomprehensible.
The way things are going, I would be amazed if we ever visited another planet. :whistle:

2005-Nov-29, 04:09 PM
The way things are going, I would be amazed if we ever visited another planet. :whistle:

Well, one would hope we could manage it! Although, the chances of that happening during my time, (optimisitically that stretches to between 2070-2100), seemed to have definitely receded since my childhood. (I'm early Generation Y - b1979).

Certainly during the 1980s it was the Voyager probes that captured my imagination, and I'm still v.v. excited by the robotic exploration of the Solar System, but definitely have to share your disappointment with the stagnation of the manned area.

I'm still optimistic I'll see men on Mars though, I'll give them a few more years before I lose hope.

2005-Nov-30, 01:54 AM
Junior Member

Here is by far the best site I have seen for what you are asking!



2005-Nov-30, 05:11 PM
I'm a little surprised none have mentioned Hubble's observational evidence.

The Hubble Ultra Deep Field found about 10,000 galaxies in an image 3 arc minutes square.

10,000 galaxies in UDF
3 arc min square
9 sq. arc minutes
1,111 no. of galaxies per sq. arc minute
3,600 sq. arc min per sq. degree
4,000,000 no. of galaxies per sq. arc degree
41,253 no of arc degrees in a sphere
165,012,000,000 Total no. of observable galaxies, probably.

[I recall a figure, however, of around 131 billion, so maybe it wasn't quite 3 arc minutes per side in the original image.]

Keep in mind, the Hubble is not powerful enough to catch all the galaxies that are actually there. So, this is a minimum number only.

2005-Nov-30, 10:12 PM
Now all we need is some clown to not sell you a star for Xmas, but an entire galaxy....what with the declining real estate prices. There outta be a law against such foolishness. Ciao. Pete.:naughty:

2005-Dec-01, 01:13 AM
A distinction should also be made for dwarf galaxies and regular spirals and ellipticals.

According to the site I referenced above there are 350 billion galaxies and 3.5 trilllion dwarf galaxies. In other words, there are 10 times more dwarfs than regular galaxies.


2005-Dec-01, 02:55 AM
I believe a good analogy of "size" of our galaxy is: If the Milky Way stretched 88 miles across, our solar system would be appx 3 cm. By the way, even in Star Trek episodes, they have not totally explored the Milky Way.