New Clues Found in Ongoing Mystery of Giant Galactic Blobs
Astronomers have numerous technical terms and numbering systems for
describing the universe, but one type of mysterious object has yet
to be classified. For now, these oddities are named for their
strange appearance. They are called blobs.
Image above: This image composite shows a giant blob (red, left) and the three merging galaxies NASA's Spitzer Space Telescope discovered within it (yellow, right). Visible light images like the one shown on the left reveal the vast extent of blobs, but don't provide much information about their host galaxies. Using its heat-seeking infrared eyes, Spitzer reveals three monstrously bright galaxies, trillions of times brighter than the Sun, in the process of merging together. Image credit: NASA/JPL-Caltech. + Click for larger image.
At the 205th annual meeting of the American Astronomical
Society in San Diego, Calif., astronomers presented new evidence in
the case of the giant galactic blobs. These blobs are huge clouds of
intensely glowing material that envelop faraway galaxies. Using
NASA's Spitzer Space Telescope and its powerful infrared vision, the
astronomers caught a glimpse of the galaxies tucked inside the
blobs. Their observations reveal monstrously bright galaxies and
suggest that blobs might surround not one, but multiple galaxies in
the process of merging together.
"It is possible that extremely bright galactic mergers lie at the
center of all the mysterious blobs, but we still don't know how they
fuel the blobs themselves," said Dr. Harry Teplitz, Spitzer Science
Center, California Institute of Technology, Pasadena, Calif., co-
author of the new research. "It's like seeing smoke in the distance
and now discovering that it's a forest fire, not a house or car
fire, but still not knowing whether it was caused by lightning or
The findings will ultimately provide a better understanding of how
galaxies, including ones like our own Milky Way, form.
Blobs were first discovered about five years ago with visible-light
telescopes. They are located billions of light-years away in ancient
galactic structures or filaments, where thousands of young galaxies
are clustered together. These large, fuzzy galactic halos are made
up of hot hydrogen gas and are about 10 times as large as the
galaxies they encompass. Astronomers can see glowing blobs, but they
don't know what provides the energy to light them up.
"To figure out what's going on, we need to better characterize the
galaxies at the center of the blobs," said Dr. James Colbert,
Spitzer Science Center, first author of the study.
That's where Spitzer comes in. Spitzer can sense the infrared glow
from the dusty galaxies inside the blobs. When Colbert and
colleagues used Spitzer to look at four well-known blobs located in
a galactic filament 11 billion light-years away, they discovered
that one of them appears to be made up of three galaxies falling
into each other -- an unusual cosmic event. The finding is
intriguing because previous observations from NASA's Hubble Space
Telescope found that another one of the four blobs surrounds a
merger between two galaxies. The astronomers speculate that all
blobs might share this trait; however, more evidence is needed to
close the case.
One clue that the scientists might be on the right track has to do
with the infrared brightness of the blob galaxies. To visible-light
telescopes, these galaxies appear unremarkable. Spitzer measurements
revealed that all four of the galaxies studied are among the
brightest in the universe, giving off the equivalent light of
trillions of Suns. Such luminous galaxies are often triggered when
smaller, gas-rich ones crash together, supporting the notion that
galactic mergers might make up the cores of blobs.
Even if galactic mergers are fingered as the culprit, the mystery of
the giant galactic blobs will persist. Astronomers will have to
figure out why mergers are producing such tremendous clouds of
"Far from solving the mystery of the blobs, these observations only
deepen it. Not only are the gas
clouds bizarre, we now know that they contain some of the brightest
and most violent galaxies in the universe," said Teplitz.
Other authors of this work include Dr. Paul Francis, The Australian
Canberra, Australia; Dr. Povilas Palunas, University of Texas at
Austin; Dr. Gerard Williger,
Johns Hopkins University, Baltimore, Md.; and Dr. Bruce E. Woodgate,
NASA's Goddard Space Flight Center, Greenbelt, Md.
Images and additional information about the Spitzer Space Telescope
are available at http://www.spitzer.caltech.edu/Media
Whitney Clavin (818) 648-9734
Jet Propulsion Laboratory, Pasadena, Calif.