We know the universe is enormous and stretches billions of light years in all directions, but we’re now a tiny bit better acquainted with our (comparatively) local neighbours. At 250 million light years away, the hundreds of galaxies uncovered by CSIRO’s Parkes radio telescope are – in galactic terms – right on our doorstep.

So how come we haven’t noticed them before? Blame the Milky Way. “The Milky Way is very beautiful, of course, and it’s very interesting to study our own galaxy, but it completely blocks out the view of the more distant galaxies behind it,” explained lead author Lister Staveley-Smith, director of science at the International Centre for Radio Astronomy Research.

The scientists from the University of Western Australia used the radio telescope to look beyond the Milky Way to the 883 galaxies tucked away behind. Around a third of these have never been observed before.

In order to make the discovery, researchers kitted out the observatory with a new 21-centimetre multibeam receiver, allowing it to map the sky thirteen times faster than previously possible. In total, the researchers found three new galaxy concentrations, currently dubbed with the postcode-style names of NW1, NW2 and NW3, and two new clusters – CW1 and CW2.

So we have hundreds more local galaxies than we thought. So what? We know the universe potentially has 400 billion galaxies dotted around, so why is the discovery of a few hundred more locally important? Well, for one thing, it might give us insights into a well-documented gravitational phenomenon known as the Great Attractor.

Since the 1970s, we’ve known that there’s a region of the universe that’s pulling the Milky Way and thousands of other galaxies with the gravitational force of around a million suns. It’s possible that this could shed some light on why.

“We don’t actually understand what’s causing this gravitational acceleration on the Milky Way or where it’s coming from,” explained professor Staveley-Smith. “We know that in this region there are a few very large collections of galaxies we call clusters or superclusters, and our whole Milky Way is moving towards them at more than two million kilometres per hour.”

In short, if there are hundreds more galaxies nearby than we know about, and each galaxy contains an average of a billion stars, there’s a much greater gravitational pull than we previously knew about, offering a plausible explanation for the Great Attractor. Sure, it’s just a theory for now, but it’s a good one.

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Image: ICRAR