Blob B6 is seen in red in the optical image at left. Inside the blob, seen in the infrared image at right, are three hyper-luminous galaxies. Image
Credit: NASA/JPL-Caltech/H. Teplitz (SSC/Caltech)
SAN DIEGO -- Strange objects in faraway space known to astronomers only as Giant Galactic Blobs have, upon close inspection, become a lot weirder.
The blobs are huge clouds of glowing gas. They've been puzzling astronomers since their discovery five years ago. Researchers discussed new observations of the object here today at a meeting of the American Astronomical Society.
NASA's Spitzer Space Telescope, which works like night-vision goggles to detect infrared radiation, peeked inside the blobs to reveal galaxies lurking within. Turns out there are typically two or more galaxies inside a given blob.
Take Blob B6, for example (yes, that's what astronomers call it). B6 contains a trio of galaxies, said James Colbert of Caltech's Spitzer Science Center. The galaxies are likely to merge, and that could have something to do with creation and illumination of the blobs. But merger activity alone isn't a sufficient explanation for the cosmic lightbulbs.
Three things might cause the blobs hydrogen to glow, Colbert said.
- Radiation from matter being superheated as it swirls into black holes at the galaxies' centers
- Superwinds of material from mass quantities of exploding stars
- Energy released by gas that cools as it falls into the center of a galaxy
"It is possible that extremely bright galaxy mergers lie at the center of all the mysterious blobs, but we still don't know how they fuel the blobs themselves," said Harry Teplitz of the Spitzer Science Center.
The blobs are about 11 billion light-years away, seen as they existed early in the history of the universe when things were more crowded. Each is more than 400,000 light-years across, or 10 times bigger than the galaxies inside them. Each blob releases more energy than 10 billion Suns.
To optical telescopes, the four blobs of the new study are unremarkable, however. But in infrared -- the heat radiation that makes night-vision goggles work -- their inner galaxies turn out to be among the brightest in the universe, releasing 10 trillion times more energy than the Sun.
That qualifies them to be ranked as "hyper-luminous infrared galaxies," Colbert explained.
The blobs are strung along an ancient filament, some 350 million light-years long, that includes many other galaxies under construction. The crowded region of space is a hotbed of galaxy formation. Understanding the blobs could help scientists understand how the universe evolved, said Sir Martin Rees, Britain's Astronomer Royal from Cambridge University.
"Those blobs are very different from anything we see in the present universe," said Rees, who was not involved in the work.
Other studies have shown that bright infrared galaxies can be the result of collisions between gas-rich galaxies. But that doesn't explain where the colossal clouds of material come from or why they shine.
"Far from solving the mystery of the blobs, these observations only deepen it," Teplitz said. "Not only are the gas clouds bizarre, we now know that they contain some of the brightest and most violent galaxies in the universe."