Image: NASA's Goddard Space Flight Center/ESO/JPL-Caltech/DSS
Astronomers have crowned the universe's largest known spiral galaxy, a spectacular behemoth five times bigger than our own Milky Way.
The title-holder is now NGC 6872, a barred spiral found 212 million light-years away in the southern constellation Pavo, researchers announced today (Jan. 10). The distance between NGC 6872's two huge spiral arms is 522,000 light-years, compared to about 100,000 light-years for the Milky Way.
NGC 6872 has ranked among the largest known spiral galaxies for decades. But it has only now been crowned champion, after detailed study of data gathered by a number of instruments, including NASA's Galaxy Evolution Explorer spacecraft, or GALEX.
"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," lead scientist Rafael Eufrasio, of NASA's Goddard Space Flight Center in Greenbelt, Md., and the Catholic University of America, said in a statement. [Photos: 65 All-Time Great Galaxy Hits]
Eufrasio presented the results today at the 221st meeting of the American Astronomical Society in Long Beach, Calif. He stressed that spirals bigger than NGC 6872 may be out there, still waiting to be spotted and studied in depth.
NCG 6872's enormous size and odd appearance are the consequence of its gravitational interaction with a neighbor galaxy called IC 4970, which contains just 20 percent of NGC 6872's mass, researchers said.
Computer simulations suggest that IC 4970 made its closest approach about 130 million years ago, stirring up a burst of activity in certain parts of NCG 6872.
"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," Duilia de Mello, a professor of astronomy at Catholic University, said in a statement.
NGC 6872's bar, which links the galaxy's arms and its central regions, is also huge. With a radius of 26,000 light-years, it's about twice as big as the bars of nearby spirals, researchers said. No evidence of recent star formation is apparent in NGC 6872's bar, suggesting that it formed several billion years ago or more.
The $150 million GALEX mission launched in April 2003 to study the history of star formation in the universe. NASA stopped funding the mission in February 2011, and in May 2012 it handed the spacecraft's reins over to the California Institute of Technology, which is keeping the mission going with private funds.
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18 Comments
Add CommentBigger pic, please. Other than that, cool.
Reply | Report Abuse | Link to thisGolly, last time I looked, if a circle has 5 times the diameter, that's 25 times bigger. I don't know why people get hung up on an objects diameter to compare how big it is, it's like saying a bus is 3 times bigger than a car because it is 45 feet long instead of 15 feet. This is particularly irksome when discussing the size of a star, something that has a diameter 10 times bigger than our Sun has an apparent surface that is 100 times bigger and a volume that is 1,000 times greater, yet we say it is 10 times bigger. Der. I think a Galaxy that is 25 times bigger is way cooler sounding.
Reply | Report Abuse | Link to thisDoes this have anything to do with the star generator that Albert K Bender wrote about?
Reply | Report Abuse | Link to thisCurious. This is the largest 'known' spiral galaxy. Is there a theoretical size limit of how large a spiral galaxy might 'out there'?
Reply | Report Abuse | Link to thischazinMt...'bigger' isn't a defined term in measurement. It's more or less whatever you want it to be. Numbers are 'greater than' and ,as you point out, need some type of perspective. In popular culture people have poor concepts of volume, force, etc.
I would be interested in the speed of rotation at the ends of the spiral arms. It must be tremendous. Why centrifugal forces do not tear such a giant structure apart probably points to an even vaster disc of dark matter, or is there still another explanation?
Reply | Report Abuse | Link to thisIMO, peripheral structures of disk galaxies are more robust than one might think because discrete disk objects primarily gravitationally interact with relatively nearby, neighboring objects rather than any very distant central object, unlike the Solar system, which is dominated by the Sun's enormous mass.
Reply | Report Abuse | Link to thisAlso, see:
http://news.sciencemag.org/sciencenow/2013/01/scienceshot-largest-spiral-galax.html?ref=hp
It would seem that if these two galaxies were each enveloped by relatively enormous dark matter halos, the smaller galaxy would already be enveloped within the larger's dark matter halo - thought to stabilize the spiral configuration of the larger galaxy. In that case,it seems unlikely that the larger galaxy would become so radically distorted by the influence of the smaller galaxy...
For perspective, please see "Artist’s impression of the expected dark matter distribution around the Milky Way (annotated)"
http://www.eso.org/public/archives/images/screen/eso1217b.jpg
With that representation of the MW's dark matter halo in mind (produced last April), please see another very interesting, related story in the news today:
http://news.sciencemag.org/sciencenow/2013/01/has-the-milky-lost-weight.html?ref=hp
NGC 6872 must contain millions of planets that could support human life. Its my thought that the ideal planetary environment exists on one of those earth-like rocks. I define ideal as someplace with a relatively consistent temperature ranging between 70 and 80 degrees Fahrenheit; no predators; no snakes, sharks, jellyfish or spiders and nothing else poisonous; fertile soil; vegetation pretty much as we know it; white sandy beaches and a beautiful blue ocean. What the heck? I've just described Norfolk Island right here on planet earth.
Reply | Report Abuse | Link to thisVery interesting. I read your links & accompanying posts. I remember a couple of years ago reading a link you gave me on your theory on this matter & have wondered if you had any positive feedback or have further refined your theory. I am afraid it is a little beyond my time constraints & mathematics to delve much deeper. Regardless, just like climate science, I do not believe the matter is settled. Pardon the pun. It is important to keep posing questions & proposing solutions. All the best to you.
Reply | Report Abuse | Link to thisThanks so much for your kind remarks! I'm just a hacker myself, but I have encountered professionals (including my references) who had already arrived (through more scientific methods) at very similar conclusions. After some difficulty, several have been published recently. One group who had performed essentially the same analysis as those who published the revised mass estimates for the Milky Way were met with denial (mass too low) by their reviewers and are still trying to get published... I'm still annoying everyone I can, just in case it might somehow help advance the issue...
Reply | Report Abuse | Link to thisIf the speed of rotation increased in proportion with distance from the centre it would be a disc not a spiral! Think whirlpool.
Reply | Report Abuse | Link to thisThe force is entirely centripetal. There is no prospect of any object once captured accelerating to escape velocity because there is no rotational acceleration. The only way to break a stable orbit is the interference of greater gravitational force which, in an expanding Universe, ain't ever gonna happen.
That's generally correct in the Solar system, for example, where planets are primarily in stable orbits around the overwhelmingly dominant mass of the Sun, and are usually only slightly influenced by other masses.
Reply | Report Abuse | Link to thisHowever, in disk galaxies, especially anywhere near the disk periphery, stars for example continuously gravitationally interact primarily with large numbers of other, relatively nearby masses. They are essentially not directly influenced by the distant, relatively tiny mass of the centrally located supermassive black hole whatsoever. While they do, in effect, interact collectively with the billions of distant objects within the central galactic bulge (in galaxies that have a central bulge), they also interact individually with billions of much nearer objects within the disk.
In conditions where a massive object is gravitationally interacting with many other massive objects, especially in the common case of binary pairs, it is far more likely for those interactions to become unstable, producing peculiar accelerations and even expulsion.
One of the primary justifications for galactic dark matter is that it was thought that peripheral masses were rotating so fast that, without a great deal of undetected additional mass located at greater radii, they would be expelled from the galaxy. This conclusion was based on the initial assumption that 'orbiting' disk objects primarily gravitationally interacted with the center of galactic mass. Later it was presumed that the were orbiting the galactic bulge (prior to the discovery of spiral galaxies with no significant central bulge).
@frankblank: here the bigger picture:
Reply | Report Abuse | Link to thishttp://www.nasa.gov/images/content/718359main_composite_no_labels.jpg
bigger picture:
Reply | Report Abuse | Link to thishttp://www.nasa.gov/images/content/718359main_composite_no_labels.jpg
Your link did not come out correctly. Here it is:
Reply | Report Abuse | Link to thishttp://www.nasa.gov/images/content/718359main_composite_no_labels.jpg
What a pain. I'll try again: http://www.nasa.gov/images/content/718359main_composite_no_labels.jpg
Reply | Report Abuse | Link to thisAll of the links worked, even those that are partially hidden. If the issue or concern is copying the link text hidden by the damned sidebars, the entire link can still be copied by double clicking on the beginning of the url (http:), then holding down the 'shift' key while pressing the 'end' key. For multiline urls, continue to hold down the 'shift' key while pressing the 'cursor down' key as many times as necessary. The entire text should be selected, including the hidden text. Now press 'ctrl'/'c' to copy the text.
Reply | Report Abuse | Link to thisVery nice artwork -
http://www.nasa.gov/images/content/718359main_composite_no_labels.jpg
Naturally, mine link probably isn't hidden, depending on the current sidebars...
Thanks
Reply | Report Abuse | Link to thisWithin a galaxy, massive peripherial objects may be gravitationally linked to billions of massive objects-- some in the vicinity and some in distant central bulge. Gravitational interaction with remote central massive black hole may be insignificant in producing motion in the massive objects particularly in massive peripherial objects. Since a galaxy comprises of billion of massive stars and other objects spread over a large area with insignificant central mass, therefore, it is not comparable with Keplarean model like our Solar system. Radial velocity of a massive periphereal object may result from gravitational interaction of a very large nos. of massive objects along some complex model ( If really there is some model). As such, within a galaxy, there should be no need to invoke dark matter to account for the radial velocity of stars within galaxy. But majority of stars within a galaxy ( except some expulsions) operate within gravitationally stable system. In view of this, there should be some fixed non-keplarian model/laws of motion for stellar motion within galaxy. What are those laws/model which govern the stellar motion? are yet not known fully to astronomers.
Reply | Report Abuse | Link to thisHowever, a galaxy as a whole behaves a behemoth gravitationally stable system which can't be explained based upon known baryonik mass of galaxy. It is due to this reasons that scientists have to invoke dark matter halo enveloping the disc to maintain a galaxy as a gravitationally stable system