Using the Atacama Large Millimeter/submillimeter Array (ALMA), two teams of astronomers have discovered a rich inventory of molecules at the center of supernova 1987A remnant and mapped the location of these molecules to create a high-resolution 3D image of the object.
This is an artist’s impression of the SN 1987A remnant. The image is based on real data and reveals the cold, inner regions of the remnant, 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. Image credit: ALMA / ESO / NAOJ / NRAO / Alexandra Angelich, NRAO / AUI / NSF.
Supernovae — the violent endings of the brief yet brilliant lives of massive stars — are among the most cataclysmic events in the cosmos.
Though supernovae mark the death of stars, they also trigger the birth of new elements and the formation of new molecules.
On February 23, 1987, astronomers witnessed one of these events unfold inside the Large Magellanic Cloud, a neighboring dwarf galaxy some approximately 163,000 light-years away.
Over the next three decades, observations of the remnant of that explosion — SNR 1987A — revealed never-before-seen details about the death of stars and how atoms created in those stars (like carbon, oxygen, and nitrogen) spill out into space and combine to form new molecules and dust. These microscopic particles may eventually find their way into future generations of stars and planets.
Recently, two international teams of astronomers used ALMA to probe SNR 1987A.
One of the teams, led by Cardiff University astronomer Dr. Mikako Matsuura, found two previously undetected molecules, formylium (HCO+) and sulfur monoxide (SO), in this object.
These molecules were accompanied by previously detected compounds such as carbon monoxide (CO) and silicon oxide (SiO).
“This is the first time that we’ve found these species of molecules within supernovae, which questions our long held assumptions that these explosions destroy all molecules and dust that are present within a star,” Dr. Matsuura said.
The team estimates that about 1 in 1,000 silicon atoms from the exploded star can be found in SiO molecules and only a few out of every million carbon atoms are in HCO+ molecules.
It was previously thought that the massive explosions of supernovae would completely destroy any molecules and dust that may have been already present.
However, the detection of these unexpected molecules suggests that the explosive death of stars could lead to clouds of molecules and dust at extremely cold temperatures, which are similar conditions to those seen in a stellar nursery where stars are born.
“Our results have shown that as the leftover gas from a supernova begins to cool down to below 200 degrees Celsius, the many heavy elements that are synthesized can begin to harbor rich molecules, creating a dust factory,” Dr. Matsuura said.
“What is most surprising is that this factory of rich molecules is usually found in conditions where stars are born. The deaths of massive stars may therefore lead to the birth of a new generation.”
The findings are published in the Monthly Notices of the Royal Astronomical Society.
SNR 1987A as seen by ALMA. Purple area indicates emission from SiO molecules. Yellow area is emission from CO molecules. The blue ring is actual Hubble data (H-alpha) that has been artificially expanded into 3D. Image credit: ALMA / ESO / NAOJ / NRAO / R. Indebetouw.
The second team, led by Francisco Abellan of the University of Valencia, created a 3D model of SN 1987A, revealing important insights into the original star itself and the way supernovae create the basic building blocks of planets.
“When this supernova exploded, now more than 30 years ago, astronomers knew much less about the way these events reshape interstellar space and how the hot, glowing debris from an exploded star eventually cools and produces new molecules,” said co-author Dr. Rémy Indebetouw, an astronomer at the University of Virginia and the National Radio Astronomy Observatory.
“Thanks to ALMA, we can finally see cold ‘star dust’ as it forms, revealing important insights into the original star itself and the way supernovae create the basic building blocks of planets.”
The results are published in the Astrophysical Journal Letters.
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M. Matsuura et al. ALMA spectral survey of Supernova 1987A – molecular inventory, chemistry, dynamics and explosive nucleosynthesis. Mon Not R Astron Soc 469 (3): 3347-3362; doi: 10.1093/mnras/stx830
F.J. Abellán et al. 2017. Very Deep inside the SN 1987A Core Ejecta: Molecular Structures Seen in 3D. ApJL 842, L24; doi: 10.3847/2041-8213/aa784c
