超新星是星际尘埃的主要来源

Galaxies¹ can be remarkably² dusty places and supernovas are thought to be a primary source of that dust, especially in the early Universe. Direct evidence of a supernova's dust-making capabilities³, however, has been slim and cannot account for the copious⁴（丰富的） amount of dust detected in young, distant galaxies. Striking new observations with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope capture, for the first time, the remains⁵ of a recent supernova brimming with freshly formed dust. If enough of this dust makes the perilous⁶ transition into interstellar space, it could explain how many galaxies acquired their dusty, dusky appearance.

 

"We have found a remarkably large dust mass concentrated in the central part of the ejecta（喷出物） from a relatively⁷ young and nearby supernova," said Remy Indebetouw, an astronomer⁸ with the National Radio Astronomy Observatory⁹ (NRAO) and the University of Virginia, both in Charlottesville. "This is the first time we've been able to really image where the dust has formed, which is important in understanding the evolution of galaxies."

 

The results are being reported at the January meeting of the American Astronomical¹⁰ Society (AAS). They also are accepted for publication in the Astrophysical Journal Letters.

 

An international team of astronomers¹¹ used ALMA to observe the glowing remains of supernova 1987A, which is in the Large Magellanic Cloud, a dwarf¹² galaxy¹³ orbiting the Milky¹⁴ Way approximately 168,000 light-years from Earth. Light from this supernova arrived at Earth in 1987, inspiring its name. This makes 1987A the closest observed supernova explosion since Johannes Kepler's observation of a supernova inside the Milky Way in 1604.

 

Astronomers predicted that as the gas cooled after the explosion, large amounts of molecules¹⁵ and dust would form as atoms of oxygen, carbon, and silicon¹⁶ bonded¹⁷ together in the cold central regions of the remnant. However, earlier observations of 1987A with infrared¹⁸ telescopes, made within the first 500 days after the explosion, detected only a small amount hot dust.

 

With ALMA's unprecedented¹⁹ resolution and sensitivity, the research team was able to image the far more abundant cold dust, which glows brightly in millimeter and submillimeter light. The astronomers estimate that the remnant now contains about 25 percent the mass of our Sun in newly formed dust. They also found that significant amounts of carbon monoxide and silicon monoxide have formed.

 

"1987A is a special place since it hasn't mixed with the surrounding environment, so what we see there was made there," said Indebetouw. "The new ALMA results, which are the first of their kind, reveal a supernova remnant chock full of material that simply did not exist a few decades ago."

分享到：