Hundreds of Galaxies Found Behind Milky Way

February 11, 2016

Hundreds of galaxies have been playing a cosmic game of hide and seek, and astronomers just tagged them “it”.

Using radio telescopes to peer through the dense plane of the Milky Way, researchers have spotted huge galactic gatherings that have long been obscured from view. These galaxies lie a mere 250 million light-years away—and they will only get closer, because they appear to be pulling us towards them at breakneck speed.

Scientists had suspected that galaxies existed in this region, says study co-author Renée C. Kraan-Korteweg of the University of Cape Town, South Africa. But seeing them with traditional telescopes presents a challenge.

“It was not really not that surprising, because the stars and dust in our own Milky Way block a not insignificant part of the sky from our view, in optical light that is,” she says. “So yes, we did expect that many galaxies would be lying behind the plane of the Milky Way, or the so-called Zone of Avoidance. However, we did not know anything about their distribution in space.”

Kraan-Korteweg and colleagues with the International Centre for Radio Astronomy Research had a venerable tool at their disposal. The Parkes telescope, affectionately known as “the Dish,” is a 64-meter radio telescope that has been scanning the skies from New South Wales since 1961. The telescope can peer through gas and dust to see structures shining in longer radio wavelengths.

For this study, the team added a special device called a multibeam receiver, which allowed them to conduct large-scale night sky surveys at a rate 13 times faster than previously possible. The effort identified 883 total galaxies, 240 of which hadn’t been seen before, the team reports this week in the Astronomical Journal.

This galactic cornucopia represents a huge amount of mass, which makes the team suspect that the objects play a role in the intergalactic draw of a strange region called the Great Attractor.

Decades ago, astronomers noted that our galaxy and its neighbors are headed towards a largely blank spot on the cosmic map at some 14 million miles an hour. That rate is not consistent with the speed at which the universe is thought to be expanding. Instead, the motion suggests something we can’t see is pulling us with the gravitational force of a million billion suns.

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