CAT scan of nearby supernova remnant reveals frothy interior

Posted: 29 Jan 2015 11:30 AM PST

Cassiopeia A, or Cas A for short, is one of the most well studied supernova remnants in our galaxy. But it still holds major surprises. Astronomers have now generated a new 3-D map of its interior using the astronomical equivalent of a CAT scan. They found that the Cas A supernova remnant is composed of a collection of about a half dozen massive cavities -- or 'bubbles.'

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Oh, wow!  I love this kind of thing, even though I barely understand it. I used to subscribe to Astronomy magazine, but have dropped everything that I don't need to stay alive....  Being old really sux, but as W.C. Fields, it beats the alternative.  I think.

Canadian/American SF author Spider Robinson completed a novel that Robert a. Heinlein only began to write notes for about our own sun being blown up deliberately, by nobody knew who.  It's called Variable Star, and the last I heard, he was writing a totally original sequel.  Fascinating book, I'll have to check his web site to see what he's up to...he lives on Bowen Island near Vancouver, B.C., and has had some dreadful and traumatic family stuff going on in the past few years, so I don't know how much writing he has been doing lately.

I just checked Spider's web site, and am crying.  His father died on Dec. 24th (at 90-something), but even worse, his 40-year-old daughter died of metastatic breast cancer on Dec. 5th.  His wife Jeanne, and co-author on the Stardance series died in 2010....

I cannot even begin to imagine what that man (and the rest of his family) have been through!  And I think I've got problems.  HAH!

He's still trying to work on Orphan Stars, the sequel I mentioned, but can barely force himself to type and feed himself at the moment.

Felaine, what a sad series of events. I have no read anything by Spider; his descriptions sound like a gentle man. I can't even imagine going through cancer treatments without insurance. Without insurance, I would have been wiped out, financially. 

My contribution of the constellation Cassiopeia seems silly compared to this sad news. 

Cassiopeia, one of the easy constellation to find in the sky, reveals some interesting characteristics that current technology reveals. 

We have so much light pollution in SoCal...except for some deserts and beaches...that I have to  find the Big Bear and follow the pointer stars in the bowl to find Polaris.  The Little Bear is mostly invisible.  Cassiopeia is easier to find, but the ones I look for mostly are the winter constellations; Orion, Taurus, and the Pleiades...all in the same area of the sky..

"Mini Supernova" Explosion Could Have Big Impact

In Hollywood blockbusters, explosions are often among the stars of the show. In space, explosions of actual stars are a focus for scientists who hope to better understand their births, lives, and deaths and how they interact with their surroundings.

Using NASA’s Chandra X-ray Observatory, astronomers have studied one particular explosion that may provide clues to the dynamics of other, much larger stellar eruptions.  

A team of researchers pointed the telescope at GK Persei, an object that became a sensation in the astronomical world in 1901 when it suddenly appeared as one of the brightest stars in the sky for a few days, before gradually fading away in brightness. Today, astronomers cite GK Persei as an example of a “classical nova,” an outburst produced by a thermonuclear explosion on the surface of a white dwarf star, the dense remnant of a Sun-like star.

A nova can occur if the strong gravity of a white dwarf pulls material from its orbiting companion star.  If enough material, mostly in the form of hydrogen gas, accumulates on the surface of the white dwarf, nuclear fusion reactions can occur and intensify, culminating into a  cosmic-sized hydrogen bomb blast. The outer layers of the white dwarf are  blown away, producing a nova outburst that can be observed for a period of months to years as the material expands into space.

Classical novas can be considered to be “miniature” versions of supernova explosions. Supernovas signal the destruction of an entire star and can be so bright that they outshine the whole galaxy where they are found. Supernovas are extremely important for cosmic ecology because they inject huge amounts of energy into the interstellar gas, and are responsible for dispersing elements such as iron, calcium and oxygen into space where they may be incorporated into future generations of stars and planets.

Although the remnants of supernovas are much more massive and energetic than classical novas, some of the fundamental physics is the same. Both involve an explosion and creation of a shock wave that travels at supersonic speeds through the surrounding gas.  

The more modest energies and masses associated with classical novas means that the remnants evolve more quickly. This, plus the much higher frequency of their occurrence compared to supenovas, makes classical novas important targets for studying cosmic explosions.

Chandra first observed GK Persei in February 2000 and then again in November 2013. This 13-year baseline provides astronomers with enough time to notice important differences in the X-ray emission and its properties.

This new image of GK Persei contains X-rays from Chandra (blue), optical data from NASA’s Hubble Space Telescope (yellow), and radio data from the National Science Foundation’s Very Large Array (pink). The X-ray data show hot gas and the radio data show emission from electrons that have been accelerated to high energies by the nova shock wave. The optical data reveal clumps of material that were ejected in the explosion. The nature of the point-like source on the lower left is unknown.

Over the years that the Chandra data span, the nova debris expanded at a speed of about 700,000 miles per hour. This translates to the blast wave moving about 90 billion miles during that period.

One intriguing discovery illustrates how the study of nova remnants can provide important clues about the environment of the explosion. The X-ray luminosity of the GK Persei remnant decreased by about 40% over the 13 years between the Chandra observations, whereas the temperature of the gas in the remnant has essentially remained constant, at about one million degrees Celsius. As the shock wave expanded and heated an increasing amount of matter, the temperature behind the wave of energy should have decreased. The observed fading and constant temperature suggests that the wave of energy has swept up a negligible amount of gas in the environment around the star over the past 13 years. This suggests that the wave must currently be expanding into a region of much lower density than before, giving clues to stellar neighborhood in which GK Persei resides.

A paper describing these results appeared in the March 10th issue of The Astrophysical Journal. The authors were Dai Takei (RIKEN, Spring-8 Center Japan), Jeremy Drake (Smithsonian Astrophysical Observatory), Hiroya Yamaguichi (Goddard Space Flight Center), Patrick Slane (Smithsonian Astrophysical Observatory), Yasunobu Uchimaya (Rikkyo University, Japan), Satoru Katsuda (Japanese Aerospace Exploration Agency).

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

Read More from NASA’s Chandra X-ray Observatory

Image Credit: NASA/CXC/RIKEN/D.Takei et al

Janet Anderson
Marshall Space Flight Center, Huntsville, Ala.

Megan Watzke
Chandra X-ray Center, Cambridge, Mass.


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