The space blob that glows from within

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Image caption The light from the cloud comes from hidden galaxies

The residents of Phoenixville Pennsylvania can relax. This blob may be bigger than the Milky Way, but it isn't about to consume the local cinema.

That's because Lyman Alpha Blob 1 - to give it its official title - is some 11.5 billion light years away.

Lyman blobs are some of the biggest objects in the universe. Gigantic clouds of brightly glowing gas hundreds of thousands of light years across. It's assumed they play an important role in the evolution of the early universe (as nurseries for the formation of stars and galaxies), but no one is entirely sure what's going on beneath the surface, or why they glow in the ghoulish way they do.

It could be that these enormous blobs of hydrogen gas simply heat up as they are drawn together by the force of their own gravitational attraction. Or, that the gas is scattering and obscuring the bright light emanating from galaxies in the throws of vigorous star formation - or perhaps even massive black holes - hidden at the blob's core.

Writing in the latest edition of the journal Nature a team of French and American astronomers claim to have solved the mystery.

Using the European Southern Observatory's Very Large Telescope the team, lead by Matthew Hayes from the University of Toulouse, observed LAB-1 for a total of 15 hours. The results show the light it emits is polarised in a ring around the central region - exactly what you would expect if it was coming from a series of bright objects or regions (stars and galaxies) embedded at its centre.

"We have shown for the first time" says Dr Hayes, "that the glow of this enigmatic object is scattered light from brilliant galaxies hidden within, rather than the gas throughout the cloud itself shining."

That may be just as well, because at 300 000 light years across Lyman Alpha Blob 1 is a little bit too big to be bundled up and dropped in the icy wasteland of the arctic.

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