ESO ALMA: Supernova 1987A's super dust factory

This is a composite image of supernova 1987A. 

ALMA data (in red) shows newly formed dust in the center of the remnant. 

HST (in green) and Chandra (in blue) show the expanding shockwave. 

Credit: Alexandra Angelich (NRAO/AUI/NSF); NASA Hubble; NASA Chandra

Galaxies can be remarkably 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 capabilities, however, has been slim and cannot account for the copious amount of dust detected in young, distant galaxies.

Striking new observations with the ESO 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.

Remy Indebetouw

"We have found a remarkably large dust mass concentrated in the central part of the ejecta from a relatively young and nearby supernova," said Remy Indebetouw, an astronomer with the National Radio Astronomy Observatory (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 Astronomical Society (AAS). They also are accepted for publication in the Astrophysical Journal Letters.

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.

This artist's illustration of supernova 1987A 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 energy from the supernova is colliding with the envelope of gas ejected from the star prior to its powerful detonation. 

Credit: Alexandra Angelich (NRAO/AUI/NSF)

Astronomers predicted that as the gas cooled after the explosion, large amounts of molecules and dust would form as atoms of oxygen, carbon, and silicon bonded together in the cold central regions of the remnant.

However, earlier observations of 1987A with infrared telescopes, made within the first 500 days after the explosion, detected only a small amount hot dust.

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.

More information: J. Kamenetzky et al. 2013 ApJ 773 L34. doi:10.1088/2041-8205/773/2/L34

Hubble Image: Super-freezer Supernova 1987A is a dust factory

Hubble Space Telescope image of supernova 1987A 

Credit: ESA, NASA, P. Challis and R. Kirshner

The keyhole-like shape at the centre is the remnant of the supernova explosion 1987A. 

This remnant is still expanding with a speed of 2200 km per second. 

It is believed that the surrounding ring was formed before the explosion.

Surprisingly low temperatures detected in the remnant of the supernova 1987A may explain the mystery of why space is so abundant with dust grains and molecules.

The results will be presented by Dr Mikako Matsuura at the National Astronomy Meeting 2013 in St Andrews on Friday 5 July.

In 1987, an explosion of a massive star was detected in our neighbouring galaxy, the Large Magellanic Cloud, just 170,000 light years away.

This supernova, dubbed 1987A, released approximately thousand million times more energy than that emitted by the Sun in one year.

Twenty five years later, an international team of astronomers has used the Herschel Space Observatory and Atacama Millimeter and Submillimeter Array (ALMA) to study the supernova remnant.

They found a vast reservoir of unexpectedly cold molecules and dust.

"The powerful explosion we saw in 1987 scattered elements made by star into space in the form of a very hot plasma. The gas has now cooled down to temperatures between -250 to -170 degrees Celsius.

That's surprisingly cold, comparable to the icy surface of Pluto at the edge of our Solar System. The gas has formed molecules and some has even condensed into solid grains of dust. The supernova has now become a super freezer!" said Dr Matsuura.

The Herschel observations show that the supernova produced dust and solid material equal to about 250 000 times the mass of the Earth, or three quarters of the mass of the Sun.

To date, scientists have believed that supernova remnants contain only very energetic atomic gas, detectable at optical X-ray wavelengths; the new observations show that this is not the case.

The discovery of such a large mass of dust should help us to understand how supernovae slowly spread and fill galaxies with gas, dust and small rocky particles, some of which may eventually end up in the next generation of stars and planets.

"We were surprised by the amount of dust and molecular gas in the reservoir created by the supernova 1987A. The ALMA and Herschel observations show that the reservoir contains carbon monoxide molecules equalling one tenth of the mass of the Sun. Herschel shows that the dust mass was even larger - about half the solar mass!" said Dr Matsuura.