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| The Abell 370 galaxy cluster. (NASA, ESA/Hubble, HST Frontier Fields) |
The unfortunate fact that no one is personally invited to witness a star's dying breaths is a fact of astronomy. It is rare to see a star at its final critical moment of life because it is a matter of luck.
An international team of researchers has measured the flash of light emitted by a distant supernova in three distinct moments with a little assistance from a conveniently placed cluster of galaxies.
They will be able to put their theories about what the star's dying light might tell us about its size on the basis of the data.
The star itself is far too far away to be seen in any detail with a telescope. Because it is so far away, its light has taken approximately 11.5 billion years to cross the vast space, tangled in the bright light of numerous other stars in its home galaxy.
The changes in the star's glow, on the other hand, can be seen, and they tell us a few things about how it died. And endured.
The jumble of stars happened to pass within a portion of the Abell 370 galaxy cluster, which is a group of hundreds of galaxies about 4 billion light years apart.
The close proximity of so many galaxies is bound to create a significant depression in the cosmic landscape, causing the star's light to bend slightly as it passed through.
The effect was similar to that of a huge telescope the size of a galaxy with a warped, scratched, and wrinkled lens caused by the uneven gravity.
The original light was smeared into what is known as an Einstein cross after it was copied and magnified, resulting in subtlely different versions of the distant galaxy as it appeared at various points in time.
In 2010, the Hubble Space Telescope's survey of stars yielded the ring of gravitationally lensed light, which the researchers discovered. The team was able to transform the light into something useful through some clever modeling, revealing three of the four points of the cross (the fourth was too faint to be discernible).
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| Multiple images of the supernova. (Chen et al., Nature, 2022) |
Each smear's light was examined, and the swollen glow of an exploding star, spread out over eight days, could be seen within. Six hours after the initial burst, one showed the light.
When taken as a whole, the three blurs of light show how the supernova changed from a fiery 100,000 Kelvin to a much cooler 10,000 K over a week. Dying stars of a certain size don't just vanish into thin air. They cool just enough for their cores to collapse in a furious explosion, the mother of all nuclear explosions, as they have run out of atomic fuel to start their fires.
Researchers are slowly working on figuring out exactly when a given star will explode.Finding supernova explosions' expanding gas and light shells is not difficult, but catching a dying star requires a lot of luck.
Not only did astronomers have the signature flash of a dying star in a galaxy far, far away here, but they also had crucial information about how its light changed in a short time.
Models of how the material surrounding stars reacts to the burst of radiation from within are strengthened by this information, which enables them to work backward to determine the star's original size by observing how it cools.
The team is confident that the dying star they saw had a radius greater than 530 times that of our own Sun based on what they learned in this case.
In addition to paving the way for the investigation of a brand-new population of stars from the early universe, the study provides support for theoretical models of the evolution of supernovae and the stars that produce them.
And that is as close as we will ever get to being invited into the final, fleeting moments of a star.
This research was published in Nature.
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