ALMA finds stardust

Striking new observations with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope capture, for the first time, the remains of a recent supernova brimming with freshly formed dust. If enough of this dust makes the perilous transition into interstellar space, it could explain how many galaxies acquired their dusty, dusky appearance.

ALMA observes the Universe in different frequency bands. One of those, Band 9, was designed and constructed by SRON Groningen in collaboration with staff from the University of Groningen Kapteyn Institute for Astronomy.

An international team of astronomers used ALMA to observe the glowing remains of supernova 1987A, which is in the Large Magellanic Cloud, a dwarf galaxy orbiting the Milky 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.

With ALMA’s unprecedented 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.

Supernovas, however, can both create and destroy dust grains. As the shockwave from the initial explosion radiated out into space, it produced bright glowing rings of material, as seen in earlier observations with the Hubble Space Telescope.

After hitting this envelope of gas, which was sloughed off by the progenitor red giant star as it neared the end of its life, a portion of this powerful explosion rebounded back toward the center of the remnant. At some point, this rebound shockwave will slam into these billowing clumps of freshly minted dust. It’s likely that some fraction of the dust will be blasted apart at that point. But if a good fraction survives and makes it into interstellar space, it could account for the copious dust astronomers detect in the early universe.

The new study is a follow-up of observations made by the Herschel infrared satellite, for which SRON Groningen also built an instrument.

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

Source: press NRAO release.