A failed star called an “accident” puzzled astronomers


Dan Casselden On the evening of November 3, 2018, playing video games Counter-strike, When he created the history of astronomy. Every time he died, he would jump on his laptop to check the automatic search for images of the NASA Space Telescope he was running.

Suddenly, in the early hours of the morning, something strange appeared in the field of vision. “It’s very confusing,” Casselden said. “It moves faster than anything I have found. It is weak and fast, which makes it very strange.”

Kasselden emailed the astronomers he worked with Backyard World: Planet 9 project. Once they ruled out the possibility that it was an image artifact, they realized that they were observing something completely unusual, an extremely faint object 50 light years away, burning in the Milky Way at a speed of 200 kilometers per second. It was named WISE 1534-1043, but with its unique characteristics and accidental discovery, it quickly won the “Accident. “

Astronomers now believe that Casselden has discovered a brown dwarf—a failed star that lacks the volume needed to begin nuclear fusion at its core. “It’s shaped like a star,” said Sarah Keswell, An astronomer at the University of Leicester, UK. “However, it will never gain enough mass to fuse hydrogen into helium and start burning anything.”

The discovery of the accident highlights that we still have much to know about brown dwarfs. The masses of these objects range from 13 times the estimated mass of Jupiter to 75 times or more, but the exact location of these two borders is an ongoing dilemma. “People have been arguing about this in meetings,” said Beth Biller, An astronomer at the University of Edinburgh, especially the lower limit.Although the mass of 13 Jupiters is approximately Deuteron fusion can happen-The characteristics that distinguish brown dwarfs from gas giants-the boundaries may be different. “The masses of 13 Jupiters are nothing special,” Biller said. “This is completely temporary.”

The temperature of brown dwarfs also varies greatly. Biller said the hottest surface temperature is about 2,000 degrees Celsius-“about the temperature of a candle flame.” The coldest temperature is below 200 degrees. Since they do not have their own heat source, brown dwarfs will gradually cool to these lower temperatures over billions of years. (Subdwarfs further blur the boundaries between planets and brown dwarfs, possibly even colder. One called Wise Men 0855-0714 Below freezing point. “This is the coldest object outside the solar system we know,” Biller said. )

The appearance of brown dwarfs at close range is also unclear. Despite their names–Astronomer Gil Tate proposed 1975-They may not be brown. They are more like orange or red. “For better or worse, it is treated as a name,” said David Kirkpatrick, An astronomer at the California Institute of Technology.

They also have atmospheres, and these atmospheres may show some kind of band and point storms, just like on Jupiter.Last year, Biller and her colleagues took advantage of these storms Measuring the wind speed of brown dwarfs About 34 light years away. They first observe that features in the atmosphere enter and exit the field of view as they rotate, and then compare this speed with the measured value of the internal rotation speed of the object collected from the magnetic field. Comparing these two values, the researchers calculated a wind speed of more than 2,300 kilometers per hour—more than five times the wind speed of Jupiter.

Because brown dwarfs bridge the gap between stars and planets, they can help us understand both. At the upper end of the mass scale, the boundary between the largest brown dwarf and the smallest star can give us insight into how nuclear fusion begins.The temperature an object needs to reach About 3 million degrees Celsius The core is to initiate nuclear fusion, saying Nolan Greaves University of Geneva, Switzerland; this triggers a chain reaction that converts hydrogen into helium. But no one knows exactly how much mass is needed for this to happen, and when the brown dwarf will become a star. “In many aspects of stellar evolution, our knowledge is still very uncertain,” Biller said. “Where is the limit of fusion is one of these issues.”


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