The dust reservoirs observed in two type IIP supernovae, SN 2004et and SN 2017eaw, both in the medium-sized, face-on spiral galaxy NGC 6946 about 22 million light-years away, is radiatively heated to 100-150 K (minus 173 to minus 123 degrees Celsius, minus 280 to minus 190 degrees Fahrenheit) by ongoing shock interaction with the circumstellar medium.
Hubble image of NGC 6946, the host galaxy of both SNe 2004et and 2017eaw. Bottom left-hand panel: composite image of SN 2004et taken with Webb/MIRI. Bottom right-hand panel: composite image of SN 2017eaw taken with Webb/MIRI. Image credit: NASA / ESA / CSA / Ori Fox, STScI / Melissa Shahbandeh, STScI / Alyssa Pagan, STScI.
Dust is a building block for many things in our Universe, planets in particular.
Where that dust comes from has puzzled astronomers for decades. One significant source of cosmic dust could be supernovae — after the dying star explodes, its leftover gas expands and cools to create dust.
“Direct evidence of this phenomenon has been slim up to this point, with our capabilities only allowing us to study the dust population in one relatively nearby supernova to date — SN 1987A, 170,000 light-years away from Earth,” said Dr. Melissa Shahbandeh, an astronomer at Johns Hopkins University and the Space Telescope Science Institute.
“When the gas cools enough to form dust, that dust is only detectable at mid-infrared wavelengths provided you have enough sensitivity.”
For supernovae more distant than SN 1987A like SN 2004et and SN 2017eaw, both in NGC 6946, that combination of wavelength coverage and exquisite sensitivity can only be obtained with Webb’s Mid-Infrared Instrument (MIRI).
The Webb observations are the first breakthrough in the study of dust production from supernovae since the detection of newly formed dust in SN 1987A with the Atacama Large Millimeter/submillimeter Array (ALMA) telescope nearly a decade ago.
Another particularly intriguing result of the new study isn’t just the detection of dust, but the amount of dust detected at this early stage in the supernova’s life.
In SN 2004et, Dr. Shahbandeh and colleagues found more than 5,000 Earth masses of dust.
“When you look at the calculation of how much dust we’re seeing in SN 2004et especially, it rivals the measurements in SN 1987A, and it’s only a fraction of the age,” said Dr. Ori Fox, an astronomer at the Space Telescope Science Institute.
“It’s the highest dust mass detected in supernovae since SN 1987A.”
While astronomers have confirmed that supernovae produce dust, the question has lingered about how much of that dust can survive the internal shocks reverberating in the aftermath of the explosion.
Seeing this amount of dust at this stage in the lifetimes of SN 2004et and SN 2017eaw suggests that dust can survive the shockwave — evidence that supernovae really are important dust factories after all.
“There’s a growing excitement to understand what this dust also implies about the core of the star that exploded,” Dr. Fox said.
“After looking at these particular findings, I think our fellow researchers are going to be thinking of innovative ways to work with these dusty supernovae in the future.”
The results are published in the Monthly Notices of the Royal Astronomical Society.
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Melissa Shahbandeh et al. 2023. JWST observations of dust reservoirs in type IIP supernovae 2004et and 2017eaw. MNRAS 523 (4): 6048-6060; doi: 10.1093/mnras/stad1681
