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There may be 10 times more galaxies in the universe than we thought

The universe is a staggeringly big place with more galaxies than you could fathom. It seems understandable that when dealing with such massive numbers that a few galaxies could fall through the cracks. But a new analysis of Hubble Telescope data indicates that astronomers might have vastly underestimated the scale of the universe. There may actually be 10 times more galaxies in the universe than we previously thought.

Before today, the best estimate of the number of galaxies existed in the universe came from a 1995 observation by Hubble, shortly after it was repaired in orbit. That’s when NASA used the space telescope to observe a patch of sky continuously for 10 days. The resulting image revealed a sea of galaxies in a section of space that looked empty to the unaided eye. This famous image is known as the Hubble Deep Field.

Based on the number of galaxies seen in the Deep Field, astronomers extrapolated the likely number of galaxies across the whole sky as around 200 million. The new estimate comes from Christopher Conselice of the University of Nottingham, who says the actual figure is closer to 2 trillion. So, we may have been missing 90% of the galaxies in previous estimates. How can our best guess be an order of magnitude off? Those unseen galaxies are just very, very faint. Hubble simply wasn’t designed with this in mind. Design work on Hubble started in the 1970s, and it was built mostly in the 1980s. Technology has taken leaps and bounds since then.

Hubble in orbit

Conselice and his team used deep space data from Hubble taken over years and converted them into 3D maps, applying new mathematical models to infer the existence of galaxies that can’t be observed directly. This also allowed the team to get a more accurate count of visible galaxies across the sky, rather than just extrapolating from a single frame. The study has been accepted for publication in the prominent Astrophysical Journal.

If there are indeed 2 trillion observable galaxies in the universe, astronomers will have a lot of work to do. Hubble isn’t powerful enough to observe these objects directly because they’re too distant and dim, but the upcoming James Webb Space Telescope will be much more powerful. It’s scheduled to launch in 2018 and will be able to detect much more distant objects. Only then will be able to get a proper handle on how many galaxies are waiting out there to be discovered.

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