A universe of 2 trillion galaxies

January 16, 2017 by Lindsay Brooke
Image of the HST GOODS-South field, one of the deepest images of the sky but covering just one millionth of its total area. The new estimate for the number of galaxies is ten times higher than the number seen in this image. Credit: NASA / ESA / The GOODS Team / M. Giavalisco (UMass., Amherst)

An international team of astronomers, led by Christopher Conselice, Professor of Astrophysics at the University of Nottingham, have found that the universe contains at least 2 trillion galaxies, ten times more than previously thought. The team's work, which began with seed-corn funding from the Royal Astronomical Society, appears in the Astrophysical Journal today.

Astronomers have long sought to determine how many galaxies there are in the observable , the part of the cosmos where light from distant objects has had time to reach us. Over the last 20 years scientists have used images from the Hubble Space Telescope to estimate that the universe we can see contains around 100 - 200 billion galaxies. Current astronomical technology allows us to study just 10% of these galaxies, and the remaining 90% will be only seen once bigger and better telescopes are developed.

Prof Conselice's research is the culmination of 15 years' work, part-funded by a research grant from the Royal Astronomical Society awarded to Aaron Wilkinson, an undergraduate student at the time. Aaron, now a PhD student at the University of Nottingham, began by performing the initial galaxy-counting analysis, work which was crucial for establishing the feasibility of the larger-scale study.

Prof Conselice's team then converted pencil beam images of deep space from telescopes around the world, and especially from the Hubble telescope, into 3-D maps. These allowed them to calculate the density of galaxies as well as the volume of one small region of space after another. This painstaking research enabled the team to establish how many galaxies we have missed - much like an intergalactic archaeological dig.

The results of this study are based on the measurements of the number of observed galaxies at different epochs – different instances in time - through the universe's history. When Prof Conselice and his team at Nottingham, in collaboration with scientists from the Leiden Observatory at Leiden University in the Netherlands and the Institute for Astronomy at the University of Edinburgh, examined how many galaxies there were at a given epoch they found that there were significantly more at earlier times.

It appears that when the universe was only a few billion years old there were ten times as many galaxies in a given volume of space as there are within a similar volume today. Most of these galaxies were low mass systems with masses similar to those of the surrounding the Milky Way.

Prof Conselice said: "This is very surprising as we know that, over the 13.7 billion years of cosmic evolution since the Big Bang, galaxies have been growing through star formation and mergers with other galaxies. Finding more galaxies in the past implies that significant evolution must have occurred to reduce their number through extensive merging of systems."

He continued: "We are missing the vast majority of galaxies because they are very faint and far away. The number of galaxies in the universe is a fundamental question in astronomy, and it boggles the mind that over 90% of the galaxies in the cosmos have yet to be studied. Who knows what interesting properties we will find when we study these with the next generation of telescopes?"

The new work appears in "The Evolution of Galaxy number density at Z < 8 and its implications", C. Conselice et al., The Astrophysical Journal, in press. A preprint of the paper is available on the arXiv via arxiv.org/pdf/1607.03909v2.pdf

Explore further: Observable Universe contains ten times more galaxies than previously thought

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11 comments

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RNP
3.7 / 5 (3) Jan 16, 2017
Interestingly, the linked paper also claims to solve Olbers' paradox.
Jayarava
5 / 5 (1) Jan 16, 2017
What does this say about the amount of matter in the universe?
RNP
4.4 / 5 (7) Jan 16, 2017
@Jayarava
What does this say about the amount of matter in the universe?

It changes nothing in that sense. It simply redistributes the matter at early times into smaller, fainter galaxies. These have since merged to form the larger galaxies we see around us today. Note that, in the article, Conselice says:

"It appears that when the universe was only a few billion years old there were ten times as many galaxies in a given volume of space as there are within a similar volume today."

N.B. He is referring to co-moving volume. He then says:

"Finding more galaxies in the past implies that significant evolution must have occurred to reduce their number through extensive merging of systems."
Spaced out Engineer
3 / 5 (4) Jan 16, 2017
"In 5 billion years, the expansion of the universe will have progressed to the point where all other galaxies will have receded beyond detection. Indeed, they will be receding faster than the speed of light, so detection will be impossible. Future civilizations will discover science and all its laws, and never know about other galaxies or the cosmic background radiation. They will inevitably come to the wrong conclusion about the universe......We live in a special time, the only time, where we can observationally verify that we live in a special time." L. Krauss
Spaced out Engineer
1 / 5 (3) Jan 16, 2017
This is dependent on a flat finite universe, which we think we know within 1% given the existence of Cold Dark Matter.

Olbers' paradox maybe resolved for what we may think are beautiful solutions to a universe from nothing, but triviality is approach conditional.

Null geodesics are a little melancholic, but light is still unfolding.
Ebo2
2.3 / 5 (3) Jan 16, 2017
Number of galaxies in universe: 2 trillion
Age of universe : 13.7 billion years
Galaxies formed per earth-year (on average): 146
WOW busy place with a billion stars+ in each galaxy.
That's a galaxy every second day... 'poof'!
Zzzzzzzz
3.9 / 5 (7) Jan 17, 2017
Number of galaxies in universe: 2 trillion
Age of universe : 13.7 billion years
Galaxies formed per earth-year (on average): 146
WOW busy place with a billion stars+ in each galaxy.
That's a galaxy every second day... 'poof'!

I don't think galaxy formation is linear.....
Ebo2
3 / 5 (4) Jan 17, 2017
]
I don't think galaxy formation is linear.....


No kidding... and that just makes earlier formation even more hectic. Pretty wild huh?
Cheers
derphys
not rated yet Jan 18, 2017
This very large number of observed others big worlds in parallel shows that the parallel universes predicted by equations of quantum mechanics without any collpase (Everett ) can be as real as theses worlds that we see in the sky !!!
MarkmBha
not rated yet Jan 23, 2017
...and we sit on a "pale blue dot'.
FredJose
1 / 5 (1) Jan 24, 2017
That's a galaxy every second day... 'poof'!

Well, the creator left us with a clear understanding of exactly how "fast" all those stars were created: On the fourth day He created the sun, the moon and the rest of the shining bodies we call astronomical objects. It certainly was a "poof".

Of course this must be seen as happening in our earth bound time-frame. That is the critical point in all of this. Whereas time probably passed much, much faster in the furthermost realms, enabling light to travel billions of light years to reach us here on the same day, earth itself experienced only one single day. So "POOF".

This is the best explanation for why we see galaxies billions of light years away having basically the same make up everywhere as any other - they DO NOT CONFORM TO THE BIG BANG proposals at all. Observations trump the speculative theory.

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