See that reddish cloud inside this supernova's shockwave? It's a massive plume of dust that formed shortly after the star ripped itself to shreds. The observation was made using the the brand new ALMA telescope — and it's one that will help explain how galaxies got their dusty and dim complexion.
The image above is an artistic impression of Supernova 1987A — the closest observed supernova explosion since Johannes Kepler's observation of a supernova inside the Milky Way in 1604. It's located about 160,000 light-years away in the Large Magellanic Cloud, a dwarf galaxy orbiting the Milky Way. The visualization shows the cold, inner regions of the exploded star's remnants (in red) containing a tremendous amount of dust. The outer shell, shown in lacy white and blue circles, is where the blast wave from the supernova is colliding with the envelope of gas ejected from the star just before it detonated.
Below is an actual composite image of 1987A as captured by the Atacama Large Millimeter/submillimeter Array (ALMA) telescope, Hubble, and Chandra. Its remnants are seen in light of varying wavelengths, with red indicating newly formed dust in the center (ALMA), while green (Hubble) and blue (Chandra) show the expanding shock wave.
A Remarkably Large Dust Mass
Galaxies contain a considerable amount of dust. Astronomers have speculated that supernovae are the primary source of that dust in the early Universe, but evidence has been lacking; scientists haven't been able to account for the sheer amount of dust found in young galaxies. But these new observations are reaffirming their suspicions.
"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 at the National Radio Astronomy Observatory (NRAO) and the University of Virginia, in an ESO statement. "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 dust formed as atoms of oxygen, carbon, and silicon bonded together in the cold central regions of the remnant. It's estimated that it now contains about 25% of the mass of the Sun in the newly formed dust. What's more, this dust hasn't mixed with the surrounding environment — so it's a very "pure" sample. Fascinatingly, this dust didn't even exist just a few decades ago.
Sending the Dust Into Interstellar Space
But most of this dust won't make it out alive, as what a supernova creates it can also destroy. The ESO explains:
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 NASA/ESA 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 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."
Images: ALMA (ESO/NAOJ/NRAO)/Alexandra Angelich (NRAO/AUI/NSF) | ALMA (ESO/NAOJ/NRAO)/A. Angelich. Visible light image: the NASA/ESA Hubble Space Telescope. X-Ray image: The NASA Chandra X-Ray Observatory.
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