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Echoes from Ancient Supernovae Found?
Scientists at the Lawrence Livermore National Laboratory are claiming that they may have found echoes left over from ancient supernovae. From the article: "Just as a sound echo can occur when sound waves bounce off a distant surface and reflect back toward the listener, a light echo can be seen when light waves traveling through space are reflected back toward the viewer. The light echoes were discovered by comparing images of the Large Magellanic Cloud (LMC) taken years apart. By precisely subtracting the common elements in each image and analyzing what variable objects remain, the team looked for evidence of dark matter that might distort the light of stars in a transitory way, as part of a second-generation sky survey called SuperMACHO. SuperMACHO builds on the discoveries of the MACHO project, which started at Lawrence Livermore National Laboratory in 1989."
It should be illegal to name your own project, especially with acronyms. Everything should be called "the thing we're doing" until someone unrelated comes along and names it. It would save so many horrible fake acronyms.
"...as if millions of voices suddenly cried out in terror and were suddenly silenced."
if you steal from one source, that is plagiarism, if you steal from many, well, that's just research.
http://www.google.com/search?q=define:Supernovae
http://www.google.com/search?q=define:Supernova
Well, this sounds really fascinating. I'm afraid I don't have much to add to that, so - on a slightly-related tangent - (the Magellanic Clouds) - the Opportunity Mars rover recently took pictures of the Martian sky at night that shows the Magellanic clouds. Check out the amateur image processing at Unmanned Spaceflight. There have been some amazing pics from the rovers, but this one stands out for me for emotional impact. (Mind you, I'm a sucker for schmaltz and sentiment... Boing Boing linked to a public domain radio version of "It's a Wonderful Life" the other day, I had to keep pausing it stop from bawling like a 5 year old :)
"None are more hopelessly enslaved than those who falsely believe they are free." -- Goethe
The significance of this particular story is that a thin, attenuated light echo was used to locate a supernova that is no longer visible. APOD has had far more spectacular light echoes but usually you can plainly see the primary source of the echo at the center since they are only a few years old. In this case the echoes they found were hundreds of years old- thin expanding rings of reflected light hundreds of light years in diameter- with centers that were completely dark. The echoes were only found serendipitously using digital image processing during a search for something else (dark matter).
While it wasn't a supernova, the January 2002 flash from star V838 Monocerotis in the Milky Way made a nice, photogenic light-echo quite recently. The star, its flash, and the subsequent light echo are interesting for several reasons:
1. The reason for the flash remains unexplained by theory, and the star has been posing problems for theorists ever since. Stars that make problems for theorists are always interesting.
2. Although the flash was not a supernova, it made V838 Mon the brightest star in the entire Milky Way for a few days. The star's normal intensity was about 1 Sun, but at its peak the brightness was equivalent to 600,000 Suns. (For comparison, Rigel shines with the light of 40,000 Suns, and Deneb, one of the most powerful Milky Way stars known, shines with the light of up to 250,000.) But the flash was not a supernova (not bright enough) nor a nova since the star did not lose its outer envelope. The star swelled to a huge size (it would have reached the radius of Jupiter's orbit) and remained cooler at its surface than it had been before the flash.
3. The star has a lot of interstellar dust surrounding it for light-years in every direction, which makes for good pictures as the light-echo from the flash widens and illuminates successive rings of dust around the star. (In any light-echo the rings are circular paraboloids, really, centered around the star-earth line, with the star at the focus of the paraboloid. The light echo you see is effectively reflecting off a huge "parabolic mirror" made of dust and pointing at you.)
4. V838 Mon is in the Milky Way (only 20000 light years distant) so we can get better pictures of its light echo than the light echos associated with any recent supernovas. (The closest recent supernova was SN1987A and that was in the LMC, not the Milky Way.) People discovered this thing only a few days after it happened and we now have a sequence of very nice shots covering it at all times starting at the very beginning of the echo.
V838 Mon has been featured on APOD eight times since 2002. Its light echo is now 8 years in diameter and is still vividly lighting up successive rings of crap in the vicinity of the star. There are many animations of the echo on the web but look for the more newer ones since they have more frames that include observations from 2004-2005.
No widely accepted theory has succeeded in explaining the exact mechanism that caused the flash but astronomers generally agree that V838 Mon is a member of a new class of variable star that has been seen only twice before: M31-RV, a red variable in Andromeda that had a flash in 1989, and V4332 Sagittari, a red giant in Sagittarius that flashed in 1994. Current ideas include both cannibalism of a binary companion and planet swallowing.