kregener
2nd June 2010, 09:54 AM
http://unixronin.livejournal.com/763082.html
The red supergiant variable star Betelgeuse, estimated to be 530 light years from Earth (although measurements by different means vary from 495LY to 640LY; 530LY is considered the "best compromise" measurement) is the ninth brightest star in the sky, the ninth largest star known to exist in the universe, and has the third largest apparent size as observed from Earth of any known star, after the Sun and R Doradus, which is almost three times closer to Earth. R Doradus is believed to lie 200 +/- 25 LY from Earth, and has an angular diameter of approximately 0.057 arcseconds, making it roughly 370 times the diameter of the Sun, or about 3.46 AU, where one AU is the average radius of Earth's orbit. Placed where the Sun is, R Doradus would contain all of the inner planets and most of the main asteroid belt. Betelgeuse's angular diameter of just under 0.055 arcseconds makes it almost three times larger, 950 to 1000 times larger than the Sun (8.8 to 9.3AU, or roughly to the orbit of Saturn). It is one of only about a dozen stars whose apparent size is so large it has been imaged telescopically as a visible disk rather than a point.
Why is this important?
Well, you see, Betelgeuse has been shrinking continuously since 1993, at an increasing rate. By June 2009, it had shrunk 15% from its size as measured in 1993.
But wait! There's more. It is rumored, though I have been unable to find any reliable confirmation of the source (which is claimed to be first-hand) that the latest observations from Mauna Kea show that Betelgeuse is now shrinking so fast it is no longer round. (Due to conservation of angular momentum, when a massive star collapses gravitationally, it collapses faster at the poles, becoming increasingly oblate — flattened — as its final collapse accelerates.)
What does this mean?
Well, briefly, what it means — if true — is that Betelgeuse could be within as little as weeks of a Type II (core collapse) supernova. (Astronomers have considered for some time that Betelgeuse has the potential to go supernova any time in the next thousand years or so. "Any time" may just turn out to be rather sooner than expected.)
IF this happens, not to put too fine a point on it, it will almost undoubtedly be among the most dramatic astronomical events ever observed by human eyes. A type II supernova can briefly outshine an entire galaxy ... and this one will be only a little over five hundred LY away. The supernova that created the Crab Nebula, SN 1054, was bright enough to see in daylight for 23 days, and remained visible for 653 days ... and it was 6,300 LY away. Betelgeuse is almost 12 times closer, and can be expected to appear around 140 times brighter by virtue of that alone. And as noted at the beginning of this post, Betelgeuse is the ninth largest star known to exist in the universe.
If the rumor is true, this is going to be one hell of a show, and we'll have a front-row seat. (Relatively speaking.)
(Don't panic, though. It is not believed that a Betelgeuse supernova would present any threat to Earth, and we're not anywhere near Betelgeuse's axis of rotation and therefore in no danger from a gamma-ray burst.)
http://www.co-intelligence.org/newsletter/images/arcturus-etc.jpg
http://www.co-intelligence.org/newsletter/images/antares-etc.jpg
http://spiff.rit.edu/classes/phys301/lectures/size/hst_betelgeuse.jpg
The red supergiant variable star Betelgeuse, estimated to be 530 light years from Earth (although measurements by different means vary from 495LY to 640LY; 530LY is considered the "best compromise" measurement) is the ninth brightest star in the sky, the ninth largest star known to exist in the universe, and has the third largest apparent size as observed from Earth of any known star, after the Sun and R Doradus, which is almost three times closer to Earth. R Doradus is believed to lie 200 +/- 25 LY from Earth, and has an angular diameter of approximately 0.057 arcseconds, making it roughly 370 times the diameter of the Sun, or about 3.46 AU, where one AU is the average radius of Earth's orbit. Placed where the Sun is, R Doradus would contain all of the inner planets and most of the main asteroid belt. Betelgeuse's angular diameter of just under 0.055 arcseconds makes it almost three times larger, 950 to 1000 times larger than the Sun (8.8 to 9.3AU, or roughly to the orbit of Saturn). It is one of only about a dozen stars whose apparent size is so large it has been imaged telescopically as a visible disk rather than a point.
Why is this important?
Well, you see, Betelgeuse has been shrinking continuously since 1993, at an increasing rate. By June 2009, it had shrunk 15% from its size as measured in 1993.
But wait! There's more. It is rumored, though I have been unable to find any reliable confirmation of the source (which is claimed to be first-hand) that the latest observations from Mauna Kea show that Betelgeuse is now shrinking so fast it is no longer round. (Due to conservation of angular momentum, when a massive star collapses gravitationally, it collapses faster at the poles, becoming increasingly oblate — flattened — as its final collapse accelerates.)
What does this mean?
Well, briefly, what it means — if true — is that Betelgeuse could be within as little as weeks of a Type II (core collapse) supernova. (Astronomers have considered for some time that Betelgeuse has the potential to go supernova any time in the next thousand years or so. "Any time" may just turn out to be rather sooner than expected.)
IF this happens, not to put too fine a point on it, it will almost undoubtedly be among the most dramatic astronomical events ever observed by human eyes. A type II supernova can briefly outshine an entire galaxy ... and this one will be only a little over five hundred LY away. The supernova that created the Crab Nebula, SN 1054, was bright enough to see in daylight for 23 days, and remained visible for 653 days ... and it was 6,300 LY away. Betelgeuse is almost 12 times closer, and can be expected to appear around 140 times brighter by virtue of that alone. And as noted at the beginning of this post, Betelgeuse is the ninth largest star known to exist in the universe.
If the rumor is true, this is going to be one hell of a show, and we'll have a front-row seat. (Relatively speaking.)
(Don't panic, though. It is not believed that a Betelgeuse supernova would present any threat to Earth, and we're not anywhere near Betelgeuse's axis of rotation and therefore in no danger from a gamma-ray burst.)
http://www.co-intelligence.org/newsletter/images/arcturus-etc.jpg
http://www.co-intelligence.org/newsletter/images/antares-etc.jpg
http://spiff.rit.edu/classes/phys301/lectures/size/hst_betelgeuse.jpg