Space

Hundreds of galaxies found hiding behind the Milky Way


Scientists have used radio telescopes to cut through the haze of the Milky Way, revealing hundreds of previously hidden galaxies lurking behind it.

In a study published Tuesday in the Astronomical Journal, researchers from Australia, South Africa, the United States and the Netherlands report that the galaxies — relatively close, in cosmic terms, at just 250 million light years away — could help explain a mysterious gravitational phenomenon known as the Great Attractor.

The area of sky obscured by our own galaxy’s mass is called the Zone of Avoidance, which admittedly sounds like a location name from a tabletop role-playing game. The ZoA covers about 20 percent of the sky, and scientists know it’s full of cosmic objects. But because the dust of our own galaxy obstructs our view (and the bright stars in the area make it hard to see distant ones shining) it seems like a void when you look at it with optical telescopes.

Charting the ‘slow death of the universe’

So scientists used the Parkes telescope, which uses radio waves to observe space. They detected 883 galaxies in the ZoA, about a third of which had never been spotted before.

Enter the Great Attractor: This is a region of space that sits beyond the Milky Way and pulls all nearby galaxies toward it. Scientists know it must be incredibly massive to exert that kind of gravitational force, but because it’s obscured by the Milky Way, we don’t know much about it.

“We don’t actually understand what’s causing this gravitational acceleration on the Milky Way or where it’s coming from,” lead author Lister Staveley-Smith of the University of Western Australia said in a statement. “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.”

That’s more than 1.2 million mph. Staveley-Smith and his colleagues believe that this bumper crop of new galaxies could help solve the mystery: Perhaps there are enough of them in the ZoA to collectively exert huge gravitational forces.

This isn’t to say that the case is closed: The researchers will have to do more work to calculate the mass of these previously unknown galaxies, and only then can they determine whether the newfound stars can account for the Great Attractor’s pull. Until then, we’ll just keep hurling toward the unknown at about 1.2 million mph.


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