Astronomers captured the incredibly rare sight of a star hours after it exploded

It is an unpleasant fact in astronomy that no one receives a personal invitation to watch the breath of a dying star. Watching a star at the critical moment of its demise is a matter of luck, making it a rare find.

With a little help from a well-placed group of galaxies, an international team of researchers has measured the flash of light emitted by a distant supernova at three distinct moments.

The data will allow them to test theories about what the light of a dying star can tell us about its size.

The star itself is too far from any telescope to do any detail. It’s so far away that its light took about 11.5 billion years to cross the yawning expanse, arriving at our doorstep entangled in the brilliant glow of countless other stars in its home galaxy.

However, we can notice the changes in the star’s glow, and they reveal a few things about how he died. And he lived.

Somewhere in between here and there, the chaos of starlight occurred within a section of the Abell 370 galaxy cluster — knots of several hundred galaxies about 4 billion light-years away.

Having so many galaxies close together would inevitably create a huge dimple in the cosmic scene, causing the star’s light to bend slightly as it glides.

The effect was somewhat similar to a giant telescope the size of a galaxy, with a scratched, wrinkled lens distorted by uneven gravity.

The original light was smeared into a configuration referred to as an Einstein cross, and the original light was magnified and copied, producing subtly different copies of the distant galaxy as it appeared at different moments in time.

Researchers discovered the gravitationally-lensed ring of light in a survey of stars taken by the Hubble Space Telescope in 2010. With some clever modeling, the team turned the light into something plausible, revealing three out of four points of the cross (the fourth point was too faint to visualize) .

Multiple images of the supernova. (Chin et al., temper nature2022)

Analysis of the light within each smear revealed the bulging glow of an exploding star somewhere inside, overlapping over the course of eight days. One showed the light only six hours after the initial explosion.

Taken together, the three light hazes provide details of a supernova that slowly cools over the course of a week, from 100,000 degrees Kelvin to a cooler temperature of 10,000 K.

Dying stars of a certain size do not go quietly at night. Exhausted the atomic fuel to ignite her fires, she is cooling enough for her heart to collapse with the fury that results in the mother of all nuclear explosions.

Knowing exactly when a particular star explodes is something researchers are slowly doing. While it’s not hard to find the expanding shells of gas and light from supernova explosions, catching a star at the moment of death takes a lot of luck.

Here, astronomers not only had the flash of a dying star in a distant galaxy, but they also had vital details of the changes in its light over a short period.

This information helps confirm models of how the material surrounding the stars interacts with the burst of radiation from the interior, heating up in a blink before rapidly cooling again, allowing it to work backwards to determine the original size of the star from how it cooled.

Based on what they learned in this case, the team is confident that the radius of the star they saw in its dying days is more than 530 times the diameter of our sun.

The study not only supports theoretical models about the evolution of supernovae and the stars that produce them, but also opens the way for the analysis of a whole new group of stars from the early universe.

This is as close to inviting fleeting superstar moments as we’ll ever get.

This research was published in temper nature.

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