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First Close-Up of Star Outside Our Galaxy Shows a Giant About to Blow
Astronomers zoomed in on a stellar behemoth in the Larger Magellanic Cloud, a galaxy that orbits about 160,000 light-years from the Milky Way.
In a stunning scientific and technological feat, a group of astronomers said Thursday that it had managed to take the first close-up picture of a star in another galaxy. Not only was the image a distance record for such cosmic intimacy, but the star, bulging like an overripe fruit, looks as if it is getting ready to explode.
“For the first time, we have succeeded in taking a zoomed-in image of a dying star in a galaxy outside our own Milky Way,” Keiichi Ohnaka, an astrophysicist from Andrés Bello National University in Chile, said in a news release from the European Southern Observatory, an international collaboration that runs a phalanx of powerful telescopes in Chile.
Dr. Ohnaka and colleagues described their observations in the journal Astronomy and Astrophysics.
The star goes by the name of WOH G64. It is in the Large Magellanic Cloud, a small galaxy that orbits the Milky Way at a distance of about 160,000 light-years and is visible as a large cloud of light in the Southern Hemisphere. The L.M.C. was the site of the last great supernova explosion witnessed by astronomers in 1987, an event known as SN1987a.
Observations with a spacecraft called the Infrared Astronomical Satellite in the 1980s revealed that WOH G64, once thought to be cool and dim, is actually the most luminous red supergiant star in that galaxy, a behemoth at least 2,000 times bigger than the sun.
When such big stars finally run out of the thermonuclear fuel that keeps their inner fires burning, their cores collapse. Some particularly massive stars vanish without further ado into black holes. But others rebound and explode as supernovas, spewing newly created elements into space to seed new stars and planets before settling into their final states as black holes or tiny dense neutron stars.
But before the end, massive stars can spend thousands of years or more erupting clouds of gas from their surfaces. Call it “Apocalypse Soon,” where “soon” can be a million years from now at the pace at which stars evolve.
Dr. Ohnaka and his team achieved their close-up of this process by using the Very Large Telescope, which consists of four eight-meter diameter telescopes on Cerro Paranal, Chile, and an interferometer called GRAVITY that combines the light from the telescopes to achieve the resolution of a much larger telescope.
The new photo shows the mango-shaped star surrounded by wreaths and arcs of gas and dust previously ejected by the dying star. Robert Kirshner, director of the TMT International Observatory in Hawaii and a supernova expert who is not part of Dr. Ohnaka’s team, said the image was “definitely an eye opener!” He added, “That star is a mess as it gets ready to explode.”
How long the show will go on is anybody’s guess, the astronomers said.
“If supernova 1987A is one to go by WOH G64 could first turn into a blue supergiant and blow ‘smoke rings’ while wearing an equatorial ‘belt,’” said Jacco van Loon, a team member from Keele University in England, who has been studying this stellar behemoth for years.
WOH G64 seems to have dimmed, he added, and appears to have become hotter, over the period of time in which he’s been observing it.
“We’ve never before caught such metamorphosis in the act,” he said.
While Dr. Ohnaka wasn’t sure what stage has been reached by WOH G64, he added, “I think it is interesting to stay tuned.”
Dennis Overbye is the cosmic affairs correspondent for The Times, covering physics and astronomy. More about Dennis Overbye
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