Black-Hole Powered Blobs -The Most Massive Objects in Space (Today’s Most Popular)

060727_blob_compare_02 "Blobs" might sound as scientific as an astrologer at a NASCAR rally, but it's a real astrophysical term – in fact, it's a giant one.  Blobs are immense clouds of gas -some stretch for tens of thousands of  light years- which failed to form into galaxies and instead glow in the far reaches of space where stars used to be made.  Now scientists say they've found the power source pumping that glow – black holes.

The image of the gigantic, amoeba-like structure is seen as it was when the universe was a mere two billion years old -about 12 billion years ago. Normally, Lyman-alpha emission is in the ultraviolet part of the spectrum, but Lyman-apha blobs are so distant, their light is redshifted to (longer) optical wavelengths. X-ray data (blue) indicates the presence of a supermassive black hole feeding at the center of an active galaxy embedded in the blob. Lyman-alpha blobs could represent an early phase in galaxy formation where the heating is so great it begins to limit further rapid growth of active galaxies and their supermassive black holes.

Some of the gas blobs are up to 400,000 light years across, nearly twice the diameter of the Milky Way's neighboring Andromeda Galaxy. Scientists think they formed when massive stars born early in the history of the universe exploded as supernovas and blew out their surrounding gases. Another theory is that the blobs are giant gas cocoons that will one day give birth to new galaxies.

What everyone knows about black holes can be misleading: the definition of a black hole is the event horizon, a boundary beyond which nothing – not even light – can escape.  But that doesn't mean that nothing comes out of black holes, just that they can't come back once they pass a very specific boundary. 

Black holes actually emit immense amounts of radiation (it's just that none of it comes from inside the event horizon).  As the black hole hoovers up material, the mass spirals in towards the black hole.  As it falls it's accelerated and heats up (imagine a rock falling to Earth), and hot material starts to glow.  Very hot material radiates even more energy, "glowing" all the way up to X-rays.

Observations with NASA's Chandra X-ray observatory have found black holes in several blobs about eleven billion light years from Earth, at the very edge of the system's detection ability.  They can't quite make out the other blobs yet, but they believe that every blob has a black hole core – just as galaxies do – which powers their radiation even as it eats their matter.

In fact, it's these black holes that prevents the blobs from every becoming anything else.  Such a vast cloud of matter would inevitably collapse to start creating stars unless there's something working to prop it up against gravity – the radiation from a billion-sun-sized black hole.  Which is enough to do most things.

Astronomers recently discovered a mysterious object known as Lyman-Alpha blobs – huge bodies of gas that may be precursors to galaxies.The blob, named Himiko for a legendary, mysterious Japanese queen, stretches for 55 thousand light years, a record for that early point in time. Himiko is located at a transition point in the evolution of the universe called the re-ionization epoch—it's as far back as we can see to date.

"The farther out we look into space, the farther we go back in time, " explained Masami Ouchi, a fellow at the Observatories of the Carnegie Institution who led an international team of astronomers from the U.S., Japan, and the United Kingdom. "I am very surprised by this discovery. I have never imagined that such a large object could exist at this early stage of the universe's history. According to the concordance model of Big Bang cosmology, small objects form first and then merge to produce larger systems. This blob had a size of typical present-day galaxies when the age of the universe was about 800 million years old, only 6% of the age of today's universe!"

Astronomers are puzzled by the object, which they think could be ionized gas powered by a super-massive black hole; a primordial galaxy with large gas accretion; a collision of two large young galaxies; super wind from intensive star formation; or a single giant galaxy with a large mass of about 40 billion Suns.

Extended blobs discovered thus far have mostly been seen at a distance when the universe was 2 to 3 billion years old. No extended blobs have previously been found when the universe was younger. s from the scattering of photons created by ionized gas clouds.

Himiko was an extraordinarily bright and large candidate for a distant galaxy. "We hesitated to spend our precious telescope time by taking spectra of this weird candidate. We never believed that this bright and large source was a real distant object. We thought it was a foreground interloper contaminating our galaxy sample," continued Ouchi. "But we tried anyway. Then, the spectra exhibited a characteristic hydrogen signature clearly indicating a remarkably large distance—12.9 billion light years!"

"Using infrared data from NASA's Spitzer Space Telescope and the United Kingdom Infrared Telescope, radio data from the VLA, and X-ray imaging from the XMM-Newton satellite, we were able to estimate the star-formation rate and stellar mass of this galaxy and to investigate whether it contains an active nucleus powered by a super-massive black hole," remarked James Dunlop a team member at Edinburgh. "We found that the stellar mass of Himiko is an order of magnitude larger than other objects known at a similar epoch, but we cannot as yet tell if the center houses an active and growing black hole."

"One of the puzzling things about Himiko is that it is so exceptional," said Carnegie's Alan Dressler, a member of the team. "If this was the discovery of a class of objects that are ancestors of today's galaxies, there should be many more smaller ones already found—a continuous distribution. Because this object is, to this point, one-of-a-kind, it makes it very hard to fit it into the prevailing model of how normal galaxies were assembled. On the other hand, that's what makes it interesting!"

"Something this large and this dense would have been rare in the early universe," said  Ryosuke Yamauchi from Tohoku University. "The structure we discovered and others like are probably the precursors of the largest structures we see today which contain multiple clusters of galaxies."

Luke McKinney with Casey Kazan

Image above shows a comparison of a Lyman alpha blob and the Andromeda Galaxy. In the upper right corner is an image of the Andromeda Galaxy, scaled as if were at the same distance as the blob. The red circle indicates a bubble like structure discovered with the Subaru telescope observations. Credit: University of Tokyo Kiso Observatory 

Sources:

http://www.sciencedaily.com/releases/2009/04/090422151828.htm

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