I apologize about my rather shoddy posting of this news. I'm so bad at posting whole pages from NASA and making them look anything like good.http://www.nasa.gov/mission_pages/galex ... 30110.html wrote: This composite of the giant barred spiral galaxy NGC 6872 combines visible light images from the European Southern Observatory's Very Large Telescope with far-ultraviolet (1,528 angstroms) data from NASA's GALEX and 3.6-micron infrared data acquired by NASA's Spitzer Space Telescope. A previously unsuspected tidal dwarf galaxy candidate (circled) appears only in the ultraviolet, indicating the presence of many hot young stars. IC 4970, the small disk galaxy interacting with NGC 6872, is located above the spiral's central region. The spiral is 522,000 light-years across from the tip of one outstretched arm to the tip of the other, which makes it about 5 times the size of our home galaxy, the Milky Way. Images of lower resolution from the Digital Sky Survey were used to fill in marginal areas not covered by the other data. Credit: NASA's Goddard Space Flight Center/ESO/JPL-Caltech/DSS
The spectacular barred spiral galaxy NGC 6872 has ranked among the biggest stellar systems for decades. Now a team of astronomers from the United States, Chile and Brazil has crowned it the largest-known spiral, based on archival data from NASA's Galaxy Evolution Explorer (GALEX) mission, which has since been loaned to the California Institute of Technology, Pasadena, Calif.
Measuring tip-to-tip across its two outsized spiral arms, NGC 6872 spans more than 522,000 light-years, making it more than five times the size of our Milky Way galaxy.
"Without GALEX's ability to detect the ultraviolet light of the youngest, hottest stars, we would never have recognized the full extent of this intriguing system," said lead scientist Rafael Eufrasio, a research assistant at NASA's Goddard Space Flight Center in Greenbelt, Md., and a doctoral student at Catholic University of America in Washington. He presented the findings Thursday at the American Astronomical Society meeting in Long Beach, Calif.
The galaxy's unusual size and appearance stem from its interaction with a much smaller disk galaxy named IC 4970, which has only about one-fifth the mass of NGC 6872. The odd couple is located 212 million light-years from Earth in the southern constellation Pavo.
Astronomers think large galaxies, including our own, grew through mergers and acquisitions -- assembling over billions of years by absorbing numerous smaller systems.
Intriguingly, the gravitational interaction of NGC 6872 and IC 4970 may have done the opposite, spawning what may develop into a new small galaxy.
"The northeastern arm of NGC 6872 is the most disturbed and is rippling with star formation, but at its far end, visible only in the ultraviolet, is an object that appears to be a tidal dwarf galaxy similar to those seen in other interacting systems," said team member Duilia de Mello, a professor of astronomy at Catholic University.
Anyway, to me the news about the super-huge galaxy is fascinating. The fact that its size was unknown, because its outermost parts can only be detected in ultraviolet light (and not in infrared), is very interesting to me, too. I personally think that too little attention is given to imaging galaxies in ultraviolet light, and too much time is devoted to imaging them in infrared light. Of course, that's just my opinion.
It is true, however, that ultraviolet photography does reveal galactic features that hadn't been discovered at other wavelengths. Examples are NGC 4625 and M83.
Anyway, I thought I'd celebrate giant galaxy NGC 6872 by posting some previous great images of it. [url=Sydney Girls High School Astronomy Club,
Travis Rector (Univ. Alaska), Ángel López-Sánchez (Australian Astronomical Obs./ Macquarie Univ.), Australian Gemini Office]Here[/url] is a link to a beautiful picture of it by Sydney Girls High School Astronomy Club, Travis Rector (Univ. Alaska), Ángel López-Sánchez (Australian Astronomical Obs./ Macquarie Univ.), Australian Gemini Office.
And here is a great Hubble image of NGC 6872, processed by Starship Asterisk*'s own geckzilla.
Ann
, especially the green refraction(?) spikes. But i couldn't see the whole picture when i clicked on it to make it bigger. It would only scroll so far in either direction. 
