Astronomers Discover Star-Studded Galaxy Tail

Jun 17, 2010
NASA's Galaxy Evolution Explorer found a tail behind a galaxy called IC 3418. The star-studded tail can be seen in the image on the left, as detected by the space telescope in ultraviolet light. The tail has escaped detection in visible light, as shown by the image on the right. Credit: NASA/JPL-Caltech

(PhysOrg.com) -- NASA's Galaxy Evolution Explorer has discovered a galaxy tail studded with bright knots of new stars. The tail, which was created as the galaxy IC 3418 plunged into the neighboring Virgo cluster of galaxies, offers new insight into how stars form.

"The gas in this galaxy is being blown back into a turbulent wake," said Janice Hester of the California Institute of Technology in Pasadena, lead author of a recent study published in the . "The gas is like sand caught up by a stiff wind. However, the particular type of gas that is needed to make stars is heavier, like pebbles, and can't be blown out of the galaxy. The new Explorer observations are teaching us that this heavier, star-forming gas can form in the wake, possibly in swirling eddies of gas."

Collisions between galaxies are a fairly common occurrence in the universe. Our galaxy will crash into the Andromeda galaxy in a few billion years. Galaxies tangle together, kicking gas and dust all around. Often the battered galaxies are left with tails of material stripped off during the violence.

Hester and her team studied the tail of IC 3418, which formed in a very different way. IC 3418 is mingling not with one galaxy, but with the entire Virgo cluster of galaxies 54 million light-years away from Earth. This massive cluster, which contains about 1,500 galaxies and is permeated by hot gas, is pulling in IC 3418, causing it to plunge through the cluster's gas at a rate of 1,000 kilometers per second, or more than 2 million miles per hour. At this incredible speed, the little galaxy's gas is being shoved back into a choppy tail.

The astronomers were able to find this tail with the help of the Galaxy Evolution Explorer. Clusters of massive, young stars speckle the tail, and these stars glow with ultraviolet light that the space can see. The young stars tell scientists that a crucial ingredient for - dense clouds of gas called molecular hydrogen - formed in the wake of this galaxy's plunge. This is the first time astronomers have found solid evidence that clouds of molecular hydrogen can form under the violent conditions present in a turbulent wake.

"IC 3418's tail of star-formation demonstrates that strong turbulence promotes cloud formation," said Mark Seibert, a co-author of the paper and a member of the Galaxy Evolution Explorer science team at the Carnegie Institute for Science in Pasadena.

Hester added that galaxy tails provide the perfect environment for isolating the factors controlling star formation.

"These tails are unique, exotic locations where we can probe the precise mechanisms behind star formation," said Hester. "Understanding star formation is pivotal to understanding the lifecycles of galaxies and the dramatic transformations that some undergo. We can also study how the process affects the development of planets like our own."

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User comments : 4

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TimESimmons
1.7 / 5 (6) Jun 17, 2010
I offer you an explanation for the tail and the fact that the tail is forming stars:-

http://www.presto...ndex.htm
yyz
5 / 5 (2) Jun 18, 2010
This phenomena of ram-pressure stripping seems to play a important role in the evolution of galaxies within galaxy clusters. As galaxies move through the intracluster medium, gas is shocked and pulled from the disk of the galaxy itself, only to eventually cool and fall toward the cluster center (some gas may also form stars outside the confines of a galaxy, as seen here). The galaxy itself is soon stripped of material for making stars, thereby evolving into so-called "red and dead" galaxies found in most galaxy clusters.

Active ram-pressure stripping can only be studied in detail in relatively nearby galaxy clusters (IC 3418 is in the nearby Virgo Cluster). Other examples:

ESO 137-001 in the Norma Cluster: http://chandra.ha.../eso137/

Fourteen galaxies in the Coma Cluster: http://arxiv.org/abs/1005.3874
omatumr
1 / 5 (2) Jun 19, 2010
What produced the "star-studded tail"?

Did stars along the tail form on pre-existing gravitational wells that were formed by fragmentation of a massive neutron star?

With kind regards,
Oliver K. Manuel
yyz
5 / 5 (2) Jun 19, 2010
"Did stars along the tail form on pre-existing gravitational wells that were formed by fragmentation of a massive neutron star?"

From the abstract:

"The tail is similar to the few other observed star-forming tails, all of which likely formed during RPS [Ram Pressure Stripping]. The tails' morphologies reflect the forces present during their formation and can be used to test for dynamical coupling between molecular and diffuse gas, thereby probing the origin of the star-forming molecular gas."

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