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

It is an inconvenient truth of astronomy that no one receives a personal invitation to witness the dying breaths of a star. Catching a glimpse of a star at a critical moment in its demise is a matter of luck, making it a rare find.

With a little help from a well-placed galaxy cluster, an international team of researchers has measured the flash of light emitted by a distant supernova at three different times.

The data will allow them to test theories about what the star’s dying light might tell us about its size.

The star itself is too distant for any telescope to make out in any detail. It is so distant that its light has taken some 11.5 billion years to travel across the yawning expanse, arriving at our doorstep amid the brightness of countless other stars in its home galaxy.

However, we can observe changes in the star’s brightness, and they reveal a few things about how it died. And lived

Somewhere between here and there, the starlight disaster happened within a section of the Abell 370 galaxy cluster – a knot of several hundred galaxies some 4 billion light years away.

Having so many galaxies together is bound to put a big dent in the cosmic landscape, causing the starlight to bend slightly as it slips by.

The effect was a bit like that of a giant telescope the size of a galaxy, one with a scratched, wrinkled lens warped by uneven gravity.

Smeared in a configuration called an Einstein crossthe original light was amplified and copied, producing subtly different versions of the distant galaxy as it appeared at different points in time.

Researchers discovered the ring of gravitational lensing light in a survey of stars by the Hubble Space Telescope in 2010. Using a clever model, the team turned the light into something sensible, revealing three of the four points of the cross (the fourth was too faint to make out).

An analysis of the light within each smear revealed the growing glow of an exploding star somewhere within, staggered over eight days. One of them showed light only six hours after the initial burst.

Together, the three blurs of light provide details of the supernova slowly cooling over a week, from about 100,000 degrees Kelvin to a much cooler 10,000 K.

Dying stars of a certain size do not go quietly into the night. Exhausted from the atomic fuel to fuel their fires, they cool enough for their cores to collapse with a fury that results in the mother of all nuclear explosions.

To know precisely when a certain star will go bang is something that researchers are slowly working on. While the expanding shells of gas and light from supernova explosions aren’t hard to find, 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 galaxy far, far away, but also vital details about changes in its light over a short period.

This information helps confirm models of how the material surrounding stars interacts with the burst of radiation from within, heating up in a flash before quickly cooling again, allowing them to work backwards to determine the original size of the star based on how it cools.

Based on what they learned in this case, the team is confident that the star they witnessed in its dead moments had a radius more than 530 times that of our own Sun.

The study not only supports theoretical models about the evolution of supernovae and the stars that produce them, but also paves the way for analyzing a whole new population of stars in the early Universe.

And that’s as close to an invitation to a star’s last fleeting moments as we’ll ever get.

This research was published in Nature.