Astronomers have used NASA’s Chandra X-ray Observatory to produce a new X-ray image of NGC 1929, a star cluster embedded in the N44 nebula, which is found in the Large Magellanic Cloud.
This X-ray image shows the star cluster NGC 1929 (NASA / CXC / U. Mich. / S. Oey)
Many new stars, some of them very massive, are forming in the star cluster NGC 1929. The massive stars produce intense radiation, expel matter at high speeds, and race through their evolution to explode as supernovas.
The winds and supernova shock waves carve out huge cavities called superbubbles in the surrounding gas. The Chandra data reveal hot regions created by these winds and shocks.
The astronomers have also released a composite image of NGC 1929. Infrared data from NASA’s Spitzer Space Telescope outline where the dust and cooler gas are found. The optical light from ESO’s Max-Planck Telescope shows where ultraviolet radiation from hot, young stars is causing gas in the nebula to glow.
Composite image of NGC 1929: IR data are shown in red, the optical light is shown in yellow, X-rays are in blue (IR: NASA / JPL, optical: ESO /WFI, X-rays: NASA / CXC / U. Mich. / S. Oey)
A long-running problem in high-energy astrophysics has been that some superbubbles in the Large Magellanic Cloud, including N44, give off a lot more X-rays than expected from models of their structure.
A recent study, published in 2011 in the Astrophysical Journal, showed that there are two extra sources of the bright X-ray emission: supernova shock waves striking the walls of the cavities, and hot material evaporating from the cavity walls.
The new observations show no evidence for an enhancement of elements heavier than hydrogen and helium in the cavities, thus ruling out this possibility as an explanation for the bright X-ray emission.
This is the first time that the data have been good enough to distinguish between different sources of the X-rays produced by superbubbles.
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Bibliographic information: Jaskot et al. 2011. Observational Constraints on Superbubble X-ray Energy Budgets. ApJ 729, 28; doi: 10.1088/0004-637X/729/1/28
