Supernova Dust Factory Spotted By ALMA

One square degree image of the Tarantula Nebula and its surroundings. The spidery nebula is seen in the upper-centre of the image. Slightly to the lower-right, a web of filaments harbours the famous supernova SN 1987A. Many other reddish nebulae are visible in the image, as well as a cluster of young stars on the left, known as NGC 2100. Technical information: the image is based on observations carried out by Joao Alves (Calar Alto, Spain), Benoit Vandame and Yuri Beletsky (ESO) with the Wide Field Imager (WFI) at the 2.2-m telescope on La Silla. These data consist of a 2×2 WFI mosaic in the B- and V-bands, and in the H-alpha and [OIII] narrow bands. The data were first processed with the ESO/MVM pipeline by the Advanced Data Products (ADP) group at ESO. 
Credit: ESO/R. Fosbury (ST-ECF)

 

An international team of astronomers used ALMA to observe the glowing remains of Supernova 1987A [2], which is in the Large Magellanic Cloud, a dwarf galaxy orbiting the Milky Way about 160 000 light‐years from Earth. SN 1987A is 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 dust would form as atoms of oxygen, carbon, and silicon bonded together in the cold central regions of the remnant. However, earlier observations of SN 1987A with infrared telescopes, made during the first 500 days after the explosion, detected only a small amount of hot dust.

 

This artist’s illustration of Supernova 1987A is based on real data and reveals the cold, inner regions of the exploded star’s remnants (in red) where tremendous amounts of dust were detected and imaged by ALMA. This inner region is contrasted with the outer shell (lacy white and blue circles), where the blast wave from the supernova is colliding with the envelope of gas ejected from the star prior to its powerful detonation.

Credit: ALMA (ESO/NAOJ/NRAO)/Alexandra Angelich (NRAO/AUI/NSF)

 

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

“SN 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.”

Supernovae, however, can both create and destroy dust grains.

The site of the supernova is surrounded by bright glowing rings of material that were seen in earlier observations with the NASA/ESA Hubble Space Telescope. These were initially lit up by the ultraviolet flash from the original explosion, but over the past few years the ring material has brightened considerably as it collides with the expanding shockwave. 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 towards the centre of the remnant. “At some point, this rebound shockwave will slam into these billowing clumps of freshly minted dust,” said Indebetouw. “It’s likely that some fraction of the dust will be blasted apart at that point. It’s hard to predict exactly how much — maybe only a little, possibly a half or two thirds.” If a good fraction survives and makes it into interstellar space, it could account for the copious dust astronomers detect in the early Universe.

“Really early galaxies are incredibly dusty and this dust plays a major role in the evolution of galaxies,” said Mikako Matsuura of University College London, UK. “Today we know dust can be created in several ways, but in the early Universe most of it must have come from supernovae. We finally have direct evidence to support that theory.”
Notes

[1] Cosmic dust consist of silicate and graphite grains — minerals also abundant on Earth. The soot from a candle is very similar to cosmic graphite dust, although the size of the grains in the soot are ten or more times bigger than typical grain sizes of cosmic graphite grains.

[2] Light from this supernova arrived at Earth in 1987, as is reflected in the name.

 

Contacts and sources:

European Southern Observatory

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Southern Observatory (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

 

ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

This research was presented in a paper “Dust Production and Particle Acceleration in Supernova 1987A Revealed with ALMA”, by R. Indebetouw et al., to appear in the Astrophysical Journal Letters.