In October, many major news outlets ran stories saying that based on what scientists now know, there are 10 times as many galaxies in the universe as previously believed. The news was startling and made many people think that astronomers had somehow managed to spot 10 times as many galaxies using our current technology. While the news reports were accurate, they don’t completely explain the press release upon which they were based, and so here are the real facts surrounding the number of galaxies:
1. The Galaxies in Question Are Not New and Were Not Observed
Astronomers have long known that there are more galaxies out there than what we can see with our most advanced telescopes. Mathematical equations have been used to extrapolate the number of galaxies, and up until recently, scientists estimated that there were 200 billion galaxies occupying the infinite space that we call the universe.
A team from the University of Nottingham in the UK led by Christopher Conselice has developed a new way to perform these calculations that gives us a far more accurate picture of how many galaxies there are in existence. The calculations were performed using the data compiled by the Hubble Ultra-Deep Field (HUDF), which is a composite image of a region of space compiled from data collected by the Hubble Space Telescope in 2003/04, and looking back around 13 billion years.
Previous models used to calculate the number of galaxies assumed that they were evenly distributed throughout the universe. The new model, however, accounts for the fact that this is not actually how galaxies are dispersed. Based on the calculations, it can now be determined that there are 10 times the number of galaxies occupying the cosmos.
2. We’re a Long Way From Seeing These Galaxies
While we now can estimate that there are around 2 trillion galaxies occupying the universe, we’re not any closer to being able to see them all. As previously explained, the calculations above were purely mathematical and scientific, and about 90 percent of the galaxies in the observable part of the universe continue to be too faint or too far away for humans to see with our most advanced imaging technology.
3. The Number Is Still Not Accurate
The calculations using the Hubble Ultra Deep Field data are the closest we have gotten so far to estimating the number of galaxies that are currently in existence, but we do know that it’s not 100 percent accurate. After all, the current model is only able to calculate the existence of galaxies that formed up to 600 million years after the Big Bang, although scientists feel confident that there were unlikely to have been many galaxies formed during that early interval.
As far as the current estimate of 700 sextillion individual stars is concerned, that number will remain unaffected by the recent findings, though, and as Alan MacRobert explained on skyandtelescope.com recently:
“The total amount of stuff — stars and gas — hasn’t changed… The Lambda-CDM model predicts that the earliest clumps that formed in the smooth material after the Big Bang should have averaged about a million solar masses each (dark matter and normal matter combined). That’s about the mass of a typical globular cluster today, and a millionth the total mass of the Milky Way. That’s the mass down to which Conselice’s team ran their extrapolations to come up with their count.”