A surprisingly bright superbubble

Aug 30, 2012
The star cluster NGC 1929 contains massive stars that produce intense radiation, expel matter at high speeds, and race through their evolution to explode as supernovas. The winds and shock waves carve out huge cavities called superbubbles in the surrounding gas. X-rays from Chandra (blue) in this composite image reveal the regions created by these winds and shocks, while infrared data from Spitzer (red) outline where the dust and cooler gas are found. Optical light from an ESO telescope in Chile (yellow) shows where ultraviolet radiation from the young stars is causing the gas to glow. Credit: X-ray: NASA/CXC/U.Mich./S.Oey, IR: NASA/JPL, Optical: ESO/WFI/2.2-m

(Phys.org)—This composite image shows a superbubble in the Large Magellanic Cloud (LMC), a small satellite galaxy of the Milky Way located about 160,000 light years from Earth.

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 , 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.

X-rays from NASA's Chandra X-ray Observatory (blue) show hot regions created by these winds and shocks, while infrared data from NASA's (red) outline where the dust and cooler gas are found. The optical light from the 2.2-m Max-Planck-ESO telescope (yellow) in Chile shows where 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. These models assume that hot, X-ray emitting gas has been produced by winds from massive stars and the remains of several supernovas. A Chandra study published in 2011 showed that there are two extra sources of N44's X-ray emission not included in these models: supernova striking the walls of the cavities, and hot material evaporating from the cavity walls.

The Chandra observations also show no evidence for an enhancement of elements heavier than hydrogen and helium in the cavities, thus ruling out this possibility as a third explanation for the bright X-ray emission. Only with long observations making full use of the capabilities of Chandra has it now become possible to distinguish between different sources of the 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.

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cantdrive85
1 / 5 (8) Aug 30, 2012
"Students using astrophysical textbooks remain essentially ignorant of even the existence of plasma concepts, despite the fact that some of them have been known for half a century. The conclusion is that astrophysics is too important to be left in the hands of astrophysicists who have gotten their main knowledge from these textbooks. Earthbound and space telescope data must be treated by scientists who are familiar with laboratory and magnetospheric physics and circuit theory, and of course with modern plasma theory."
[Lamenting the traditional neglect of plasma physics]
— Hannes Alfvén

Such is the case represented in the article above, there are no less than a dozen misrepresentations of well known aspects of plasma characteristics mentioned above.
cantdrive85
1 / 5 (8) Aug 30, 2012
There is no gas and dust, all of it is plasma. The "wind" is the plasma being accelerated by the electric field of the star, the "superbubbles" are in fact the star's own heliospheres, that is the EM field created by a charged object immersed within a larger electric field. The "shockwaves" are the double layers (not cavity walls) that are created as the insulation medium between the two electric fields where a great deal of electrical energy is stored and is energetic enough to show in glow mode, which handily explains the mysterious X-rays emitted from there. The stars are not "exploding" in the sense that they describe but are more likely experiencing exploding double layers (just like CME's on our Sun but on a larger scale)due to intense fluctuations of the electrical input powering the stars, it is this extra energy flowing through the star's heliosphere that explains why the "superbubble" is in glow mode. This is the same effect that causes the nebula to glow.
seb
1 / 5 (1) Aug 31, 2012
There is no gas and dust, all of it is plasma.

That's as valid a theory as the article's stuff, no doubt. But theory is theory.

cantdrive85
1 / 5 (2) Aug 31, 2012
There is no gas and dust, all of it is plasma.

That's as valid a theory as the article's stuff, no doubt. But theory is theory.


Actually, even NASA acknowledges that in excess of 99% of the visible Universe is plasma. Some scientists, however still relate to plasma as a gas, which it absolutely is not. Plasma is a distinct state of matter, it's less an error in semantics and more of an error in understanding.

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