An annotated artist's impression showing radio waves travelling from the new galaxies, then passing through the Milky Way and arriving at the Parkes radio telescope on Earth (not to scale).
Our Milky Way may be beautiful, but it sure can ruin our view of the cosmos.
Now, astronomers have just taken a peek behind the mess of stars and dust to find a veritable galactic zoo in a previously unexplored region of space. But we’re not talking about just one or two galaxies; researchers have applied a new survey technique using the Australia-based Parkes radio telescope to find hundreds of undiscovered galaxies.
“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,” said Lister Staveley-Smith, of The University of Western Australia and International Centre for Radio Astronomy Research (ICRAR).
A total of 883 galaxies have been identified within 250 million light-years from Earth, a third of which have never been seen before. They are all located in the "Zone of Avoidance", a region of space usually inaccessible to telescopes beyond the Milky Way's galactic bulge.
Staveley-Smith’s team are investigating the mysterious “Great Attractor” — a region of space that appears to be pulling local galaxies (including the Milky Way) with an immense gravitational force the equivalent of a million billion suns. There are few satisfactory explanations for the phenomenon, but seeing “behind” the Milky Way could add a critical piece to the cosmic puzzle.
“We don’t actually understand what’s causing this gravitational acceleration on the Milky Way or where it’s coming from,” Staveley-Smith said in a ICRAR press release. “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 kilometers per hour.”
His team has mapped three dense concentrations of galaxies (named NW1, NW2 and NW3) and two new galaxy clusters (CW1 and CW2) that may be contributing to the large-scale flow of galaxies in that direction.
“We’ve used a range of techniques but only radio observations have really succeeded in allowing us to see through the thickest foreground layer of dust and stars,” said collaborator Renée Kraan-Korteweg of the University of Cape Town. “An average galaxy contains 100 billion stars, so finding hundreds of new galaxies hidden behind the Milky Way points to a lot of mass we didn’t know about until now.”