"Brightest Supernova Ever" Reveals New Kind of Star Death
"To laymen not familiar with the term “light year" This is how scientist measure distance in space." one light year (1) is the distance light travels in a (1) year. Which is 5.8 trillion miles. So when they use the expression one or two light years, every one (1) light year is 5.8 trillion miles.
The brightest star explosion ever seen has been spotted about 240 million light-years away in the constellation Perseus, researchers announced Monday, May 7, 2007 The distant event, which so far has remained brighter than an ordinary supernova for more than 200 days, likely represents a new and extremely rare type of star death that occurs only in super massive stars.
"It's no surprise that a very massive star will eventually collapse," David Pooley, an astrophysicist at the University of California, Berkeley, and co-author of a new study on the supernova, said during a press briefing. But what surprised scientists is that the brightness of the explosion couldn't be explained by the faint amount of x-rays emitted by the blast.
Normally when a large star dies, the explosion sends shockwaves through surrounding cooler gases, creating regions that emit large amounts of x-rays—the source of a supernova's light. But the explosion of SN 2006gy, which is thought to be nearly 150 times as massive as the sun, showed few x-rays.
This suggests that the light is being produced from hot material being ejected into space. "This would require a new type of [explosion] mechanism that has been produced theoretically but never observed," study leader Nathan Smith said at the briefing.
The finding has ramifications for Eta Carinae, the most massive star in our galaxy, which lies just 7,400 light years away. This star, estimated to be 100 to 120 times the sun's mass, has been experiencing preliminary eruptions that could mean it will explode in a manner similar to SN 2006gy. If such a supernova occurred in our galaxy, "it would be so bright that you could see it [from Earth] during the day and you could even read a book by its light at night," Pooley said.
Cosmic Instability
For their study, Smith, Pooley, and colleagues examined images of SN 2006gy taken from space by NASA's Chandra X-Ray Observatory and from the ground by the Lick Observatory in California and the Keck Observatory in Hawaii.
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The results will appear in an upcoming issue of Astrophysical Journal. The team surmised that the explosion was the first recorded example of a type of supernova called a pair-instability mechanism, which was first proposed in scientific literature in the 1960s.
The phenomenon has likely never been seen until now because today such extreme stellar bodies are few and far between. "Like people over seven feet [two meters] tall, stars that are over a hundred times the mass of our sun are very rare," Smith said. In such heavy stars, radiation created by fusion in the core balances the pressure of the star's gravity. When fusion stops, the star begins to collapse, crunching its core into a black hole or neutron star. In the subsequent explosion, the star emits material equal to only about 5 percent of the sun's mass.
More images taken from Chandra X-Ray observatory
Ruby slippers
Chandra reveals Jupiter's poles glowing with x-rays, colored in crimson. The most intense hotspot, at the north pole, pulsates every 45 minutes. This new image of Jupiter turns an old theory on its head. Scientists once believed that Jupiter emitted x-rays fueled by ions from Io, the planet's volcanic moon. But ions from Io would not reach these high polar latitudes, so scientists now think that the high-energy particles might come from the outer reaches of Jupiter's magnetosphere, where heavy ions from the sun interact with Jupiter's magnetic field. The particles likely hit Jupiter's atmosphere, migrate to its magnetic poles, then oscillate between the poles, causing the dramatic light show captured by Chandra
Cool heat
Neutron stars and the immense energy of black holes glow like celestial fireflies around the center of the Andromeda galaxy two million light-years from Earth. Such objects typically have a temperature of tens of millions of degrees Celsius. Chandra discovered a much "cooler" million-degree object (blue dot) about ten light-years from the center of the galaxy, perhaps a white dwarf undergoing nuclear burning on its surface. The yellow spot above the blue may be where hot gas is spiraling into the supermassive black hole at the heart of the galaxy. Chandra's sensitive eye also detected the diffuse glow (pink) of interstellar gas that extends for a thousand light-years across the galaxy's core.
Where science meets art
This spattering of purples and reds is a composite of x-ray and optical images from Chandra and the Hubble Space Telescope of NGC 4631—a spiral galaxy strikingly similar to our own Milky Way. Hubble reveals gas ionized and shaped by massive stars (colored red), and Chandra detects ghostly purple and blue x-ray energy. "This image provides long-sought evidence that a spiral galaxy is not just a disk of stars," says Chandra spokesman Wallace Tucker, "but that it is enveloped in hot gas." This finding should quell debate over the presence of multimillion-degree gas within other galaxies, including our own.
"From National Geographic News"
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