August 31, 2012
Composite Image Shows Superbubble In The Large Magellanic Cloud
April Flowers for redOrbit.com - Your Universe Online
NASA has released a hauntingly beautiful composite image showing a superbubble in the Large Magellanic Cloud (LMC). The LMC is a small satellite galaxy of the Milky Way located about 160,000 light years from Earth.A superbubble is a cavity, filled with 106 Kelvin gas blown into the interstellar medium by multiple supernovae and stellar winds, hundreds of light years across. These cavities are carved out of the surrounding gas by the shockwaves and winds from supernova explosions.
Many new stars, some of them very massive, are forming in the star cluster NGC 1929, which is embedded in the nebula N44, so named because it is the 44th nebula in a catalog of such objects in the Magellanic Clouds. The massive stars produce intense radiation, expel matter at high speeds and race through their evolution to explode as supernovas.
In the image, x-rays from NASA's Chandra X-ray Observatory (blue) show hot regions created by those winds and shockwaves. Infrared data from NASA's Spitzer Space Telescope (red) outline where the dust and cooler gas are found. Optical light from the 2.2 meter Max-Planck-ESO telescope (yellow) in Chile shows where ultraviolet radiation from hot, young stars is causing gas in the nebula to glow.
A long-running problem in high-energy astrophysics has been that some superbubbles in the LMC, including N44, give off a lot more X-rays than expected from models of their structure, which assume that hot, X-ray emitting gas has been produced by winds from massive stars and the remains of several supernovas.
Another Chandra study from 2011 showed that there are two extra sources of N44's X-ray emission not included in these models: supernova shockwaves striking the walls of the cavities, and hot material evaporating from the cavity walls. Chandra also showed no evidence for the enhancement of elements heavier than hydrogen and helium in the cavities, ruling out the possibility as an explanation for the bright X-ray emission. Only by making full use of Chandra's capabilities has it become possible to distinguish between different sources of X-rays produced by superbubbles.
The Chandra study of N44 and another superbubble in the LMC was led by Anne Jaskot from the University of Michigan in Ann Arbor. The co-authors were Dave Strickland from Johns Hopkins University in Baltimore, MD, Sally Oey from University of Michigan, You-Hua Chu from University of Illinois and Guillermo Garcia-Segura from Instituto de Astronomia-UNAM in Ensenada, Mexico.
NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.