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ESA’s Herschel infrared space telescope finds a hole in space

x024The hole has provided astronomers with a surprising glimpse into the end of the star-forming process. Stars are born in dense clouds of dust and gas that can now be studied in unprecedented detail with Herschel. Although jets and winds of gas have been seen coming from young stars in the past, it has always been a mystery exactly how a star uses these to blow away its surroundings and emerge from its birth cloud. Now, for the first time, Herschel may be seeing an unexpected step in this process.

A cloud of bright reflective gas known to astronomers as NGC 1999 sits next to a black patch of sky. For most of the 20th century, such black patches have been known to be dense clouds of dust and gas that block light from passing through. When Herschel looked in its direction to study nearby young stars, the cloud continued to look black. But wait! That should not be the case. Herschel’s infrared eyes are designed to see into such clouds. Either the cloud was immensely dense or something was wrong. Investigating further using ground-based telescopes, astronomers found the same story however they looked: this patch looks black not because it is a dense pocket of gas but because it is truly empty. Something has blown a hole right through the cloud. “No-one has ever seen a hole like this,” says Tom Megeath, of the University of Toledo, USA. “It’s as surprising as knowing you have worms tunnelling under your lawn, but finding one morning that they have created a huge, yawning pit.”

The astronomers think that the hole must have been opened when the narrow jets of gas from some of the young stars in the region punctured the sheet of dust and gas that forms NGC 1999. The powerful radiation from a nearby mature star may also have helped to clear the hole. Whatever the precise chain of events, it could be an important glimpse into the way newborn stars disperse their birth clouds.  

NGC 1999 is the green tinged cloud towards the top of the image. The dark spot to the right was thought to be a cloud of dense dust and gas until Herschel looked at it. It is in fact a hole that has been blown in the side of NGC 1999 by the jets and winds of gas from the young stellar objects in this region of space.

This image combines Herschel PACS 70 and 160 micron data, and 1.6 and 2.2 micron data with the NEWFIRM camera on the Kitt Peak 4 meter.

What they can't explain is a discovery announced a few days ago by Lawrence Rudnick, an astronomer at the University of Minnesota. He and a couple of colleagues have found what they think is another void in space — but at about a billion light-years across (that's 6 billion trillion miles, give or take), it's many times bigger than any void ever seen. It's so big, in fact, that if it's really there, it could cause real problems for all current models of the universe; the 14 or so billion years since the Big Bang isn't long enough for gravity to have cleared out a space this huge.

That's a big "if," however, as Rudnick readily acknowledges. The uncertainty comes from the fact that his discovery is circumstantial. What he and his colleagues actually found was that there's a surprising scarcity of radio galaxies — galaxies that put out unusual amounts of radio energy — in a part of the sky marked by the constellation Eridanus. That seemed odd, since radio galaxies tend to be spread about pretty evenly. Then they took a look at an entirely different set of data: microwaves emitted shortly after the Big Bang, as seen by the WMAP (or, NASA's Wilkinson Microwave Anisotopy Probe) satellite. There was a "cold" spot in the microwaves right at the same place where there weren't enough radio galaxies.

My belief is in the flesh and blood as being wiser than the intellect. The body-consciousness is where life bubbles up in us. It is how we know that we are alive, alive to the depths of our souls and in touch somewhere with the vivid reaches of the cosmos.

----- D.H. Lawrence

That could hardly be a coincidence, Rudnick thought, and the simplest solution was a great void in space. That would explain why there weren't many radio galaxies in that part of the sky. And microwaves crossing a huge void would lose some of their energy, in a complex process involving the reduced gravity inside. The exciting part is that the void is so huge that current theory simply can't explain it — and astronomers just love this kind of challenge.








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