Cosmos: Source of energy cleared by giant clouds

Galaxies inside provide Lyman alpha lumps its bright light

Lyman alpha lump LAB-1 (green) 11.5 billion light-years away from Earth in a photograph of the Very Large Telescope (VLT). © ESO / M. Hayes
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In the furthest corners of space there are gigantic clouds of glowing hydrogen that shine as bright as the brightest galaxies. Where these so-called "Lyman Alpha lumps" take their tremendous energy, was so far unclear. An international team of astronomers has now solved this puzzle. As they report in the journal "Nature", it is in the centroid of the cloud lying Galayien, which brine the gas to shine.

Lyman-alpha lumps are comparatively rare in the cosmos. They have been discovered so far, especially in very distant regions of the universe. Because their light takes several billion years to reach Earth, they reflect a very old, early state of the cosmos. Thus, they provide important information about how the first galaxies formed and evolved. Until now, however, both the exact properties of these luminous hydrogen clouds and their source of energy have been unknown. According to previous theory, the glow is produced when cold gas is sucked inward by the lump of gravity and heats up. Another theory assumed that the lumps shine because there are brightly colored objects inside. Only now is it clear that the latter assumption applies.

Polarized light reveals interactions

The Lyman-alpha lump LAB-1, which is now being studied for the first time, is 11.5 billion light-years away from Earth. It is considered one of the brightest and largest of its kind in the cosmos, measuring 300, 000 light-years from end to end. Using the Very Large Telescope of the European Southern Observatory (ESO), astronomers sighted this gas cloud, analyzing whether the cloud's light is polarized. In polarized light, all light waves vibrate in the same direction, whereas normal daylight contains waves that are unsorted in all directions. In astronomy, polarization often reveals that the light was scattered or reflected by matter on its way to Earth.

Galaxies as source of light

In the case of LAB-1, astronomers observed polarized light only in a ring around the center of the Lyman-Alpha lump. Directly inside, however, they could not detect any polarization. According to the researchers, the light must therefore come from the galaxies in the middle of the lump. It is scattered only on its way out - by the hydrogen gas of the cloud. "Our observations have shown that the glow of this strange object does not emanate from the lump itself. Instead, it is scattered light from galaxies hidden within the lump, "says Matthew Hayes of the Université de Toulouse in France.

It could be galaxies in which especially many stars are created. However, galaxies with a matter-consuming black hole are also possible in the center. This process typically releases a great deal of energy. The next goal of astronomers is to investigate more of these objects. They want to find out if the results of LAB-1 can be transferred to other lumps. (Nature, 2011; DOI: 10.1038 / nature10320) Display

(ESO, 19.08.2011 - NPO)