Danger, danger, Will Robinson…
Astronomers are keeping close watch on a monster star that erupted two years ago, ejecting about three percent of its mass over a period of about 200 days. It is not Hugh Grant.
The star, known as Rho Cas, is in the constellation Cassiopeia, about 10,000 light years away, give or take a couple of billion miles. Fascinating, Captain, but how is this relevant?
Researchers from the Harvard-Smithsonian Center for Astrophysics are asking amateur astronomers to help them keep an eye on things because the star is showing signs of going postal again. Those signs include a buildup of hydrogen, detectible through the use of a spectrometer.
Rho Cas has about 40 times the mass and 700 times the breadth of our own puny little sun. It’s visible without a telescope in the northern hemisphere, being over 500,000 times as luminous as Ol’ Sol. Imagine how much brighter Stephen Hawking is than, say, Pee Wee Herman.
Rare star types like Rho Cas are called hypergiants. This one has the annoying habit of dimming occasionally by a factor of six, indicating a drop in surface temperature from about 12,000 to 5,000 degrees Fahrenheit.
The star erupted in 1946, before astronomers had the sophisticated equipment to gauge the size of the blast or what caused it. Once they had geekier stuff with which to observe, they kept vigil for 10 years before being rewarded by the cosmic belch in 2000.
“In the spring of 2000, the star first brightened, then dimmed by a factor of 1.2 magnitudes, something unusual in any star,” said Alex Lobel of the Harvard center. “This dimming corresponds to the star shedding a shell, which produces a shock wave traveling about four times the speed of sound.”
Hypergiant stars have huge atmospheres. If Rho Cas were in our solar system, its atmosphere would extend beyond the orbit of Mars, thus putting global warming into perspective.
An image of the 2000 eructation is available at http://cfa-harvard.edu/press/pr0302-image.html.
If you want to have a shot at one-upping the experts, you can find instructions on how to do so at http://cfa-harvard.edu/iau/cbat.html.
Lessee, now. A hypergiant star that goes dim on occasion and blows up at unpredictable intervals. Should we rename it Barbra Streisand?
11:21:58 PM 
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