Astronomers starstruck by brightest star explosion

Astronomers have spotted a cataclysmic explosion that marked the death of a huge, distant star in a blast five times as bright and powerful as any they had seen previously. They said a similar fate may be imminent for a star in Earth's galactic neighbourhood.

Astronomers have spotted a cataclysmic explosion that marked the death of a huge, distant star in a blast five times as bright and powerful as any they had seen previously. They said a similar fate may be imminent for a star in Earth8217;s galactic neighbourhood.

The size and energy of the newly recorded blast, 240 million light-years away, has already begun to transform scientific understanding of how especially large stars explode, and has left awestruck researchers concerned8212;and a little excited8212;about what might happen to the similarly enormous and unstable star closer home.

If that star, named Eta Carinae, blows up like this one, they said, it could possibly spew dangerous radiation in Earth8217;s direction. More likely, however, it would erupt into the most luminous star in our sky 8212;visible during the day and bright enough to let people read unaided at night.

The new discovery of a massive star exploding in a runaway thermonuclear reaction is especially exciting for scientists, who said it gives them important clues to the nature of the early universe and the formation and destruction of the earliest stars.

8220;This was a truly monstrous explosion, a hundred times more energetic than a typical supernova,8221; astronomer Nathan Smith of the University of California at Berkeley said of the exploded star, called SN 2006gy, which was believed to be as massive as a star can be.

8220;It8217;s so powerful that it requires a new explanation of how massive stars explode,8221; Smith said. Unlike most supernovas that fade quickly, the light from this explosion has remained extremely bright since September.

Stars approaching this enormous size generally implode when they become unstable, leaving behind a black hole. Astronomers considered it theoretically possible that such a massive star could instead explode and throw vast amounts of matter into space and not collapse into a black hole, but they had never before witnessed it.

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8220;Discoveries don8217;t get more exciting than this for a theorist,8221; said Mario Livio of the Space Telescope Science Institute in Baltimore, who was not involved in the research but spoke at a NASA press conference yesterday. 8220;The suggestion is that we may be seeing a new type of explosion mechanism8212;never seen before8212;and that the first stars in the universe exploded with this mechanism,8221; he said. 8220;At the same time, there may be a star in our own galaxy that could do the same thing8212;tomorrow.8221;

Livio said enormous Eta Carinae, which is only 7,500 light years away in our Milky Way galaxy, has many features similar to the newly-discovered exploded star, and has been showing signs of instability that could lead to a similar supernova.

The potential danger comes from the fact that explosions of massive stars generally emit jets of intense gamma radiation 8212; among the most powerful and harmful forces in the universe. If Eta Carinae did explode and a jet was pointed in the general direction of the solar system, Livio said, Earth could be endangered. But because the gamma ray jets tend to be relatively narrow, like the beam of a lighthouse, the odds are that it would miss Earth.