Dwarf galaxy has giant surprise

Jan 12, 2005

Huge gas disk may be similar to stuff of early universe

An astronomer studying small irregular galaxies has discovered a remarkable feature in one of them that may provide key clues to understanding how galaxies form and the relationship between the gas and the stars within galaxies.

Liese van Zee of Indiana University Bloomington, using the National Science Foundation's Very Large Array radio telescope in New Mexico, found that a small galaxy 16 million light-years from Earth is surrounded by a huge disk of hydrogen gas that has not been involved in the galaxy's star-formation processes and may be primordial material left over from the galaxy's formation. "If that's the case, then we may have found a nearby sample similar to the stuff of the early universe," van Zee said.

"Why the gas in the disk has remained so undisturbed, without stars forming, is somewhat perplexing. When we figure out how this happened, we'll undoubtedly learn more about how galaxies form," she said.

She presented her findings on Wednesday (Jan. 12) at the national meeting of the American Astronomical Society in San Diego, Calif.

The galaxy van Zee studied, called UGC 5288, had been regarded as just one ordinary example of a numerous type called dwarf irregular galaxies. As part of a study of such galaxies, she had earlier made a visible-light image of it at Kitt Peak National Observatory in Arizona.

When she observed the galaxy later using the radio telescope, she found that it is embedded in a huge disk of atomic hydrogen gas. In visible light, the elongated galaxy is about 6,000 by 4,000 light-years, but the hydrogen-gas disk, seen with the VLA, is about 41,000 by 28,000 light-years. "The gas disk is more than seven times bigger than the galaxy we see in visible light," she said.

The hydrogen disk can be seen by radio telescopes because hydrogen atoms emit and absorb radio waves at a frequency of 1420 MHz, a wavelength of about 21 centimeters.

A few other dwarf galaxies have large gas disks, but unlike these, UGC 5288's disk shows no signs that the gas was either blown out of the galaxy by furious star formation or pulled out by a close encounter with another galaxy. "This gas disk is rotating quite peacefully around the galaxy," van Zee explained. That means, she said, that the gas around UGC 5288 most likely is pristine material that has never been "polluted" by the heavier elements produced in stars.

What's surprising, said Martha Haynes, an astronomer at Cornell University in Ithaca, N.Y., is that the huge gas disk seems to be completely uninvolved in the small galaxy's star-formation processes. "You need the gas to make the stars, so we might have thought the two would be better correlated. This means we really don't understand how the star-forming gas and the stars themselves are related," Haynes said.

It's exciting to find such a large reservoir of apparently unprocessed matter, Haynes said. "This object and others like it could be the targets for studying pristine material in the universe," she said.

Haynes was amused that a galaxy that looked "boring" to some in visible-light images showed such a remarkable feature when viewed with a radio telescope.

"This shows that you can't judge an object by its appearance at only one wavelength. What seems boring at one wavelength may be very exciting at another," Haynes said.

The National Radio Astronomy Observatory is operated under cooperative agreement by Associated Universities Inc.


Explore further: Launch pad where rocket exploded back next year

add to favorites email to friend print save as pdf

Related Stories

Hubble spies charming spiral galaxy bursting with stars

Dec 09, 2014

(Phys.org) —The NASA/ESA Hubble Space Telescope observes some of the most beautiful galaxies in our skies—spirals sparkling with bright stellar nurseries, violent duos ripping gas and stars away from ...

Warm gas pours 'cold water' on galaxy's star-making

Dec 08, 2014

Some like it hot, but for creating new stars, a cool cosmic environment is ideal. As a new study suggests, a surge of warm gas into a nearby galaxy—left over from the devouring of a separate galaxy—has ...

10 facts about the Milky Way

Dec 04, 2014

The Milky Way Galaxy is an immense and very interesting place. Not only does it measure some 100,000–120,000 light-years in diameter, it is home to planet Earth, the birthplace of humanity. Our Solar System ...

Strange galaxy perplexes astronomers

Dec 02, 2014

With the help of citizen scientists, a team of astronomers has found an important new example of a very rare type of galaxy that may yield valuable insight on how galaxies developed in the early Universe. ...

Image: Hubble views the whirling disk of NGC 4526

Oct 30, 2014

This neat little galaxy is known as NGC 4526. Its dark lanes of dust and bright diffuse glow make the galaxy appear to hang like a halo in the emptiness of space in this image from the NASA/ESA Hubble Space ...

Recommended for you

Kepler proves it can still find planets

2 hours ago

To paraphrase Mark Twain, the report of the Kepler spacecraft's death was greatly exaggerated. Despite a malfunction that ended its primary mission in May 2013, Kepler is still alive and working. The evidence ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.