April 13, 2024

The stars align: Israeli researchers track a supernova in real time

Scientists at the Weizmann Institute of Science in Rehovot have obtained the most complete view of a supernova by observing and tracking an exploding star in real time, as observed in a new study.

This discovery is a huge step forward in our understanding of one of the most important phenomena in the universe.

The findings of this study were published in the peer-reviewed academic journal Nature.

Simply put, they represent a fundamental part of the larger cosmic cycle of life, creation, death and expansion.

Stars of all types are powered by this energy production in their cores, which sees energy produced by nuclear fission fusing lighter elements to form heavier elements. It is this process that keeps the star hot, allowing gases to expand while attracting their mass towards the core in a delicate gravitational balance.

When a star can no longer produce energy, it dies. The larger stars, which are now full of heavy elements, will trigger a powerful explosion known as a supernova. This fuses some of these heavy elements to form even heavier ones, and they are all launched into the cosmos.

ASTROPHYSICIST AVISHAY GAL-YAM and researcher Ido Irani look at a screen in their laboratory at the Weizmann Institute of Science in Rehovot last week. (credit: Sebastian Rocandio/Reuters)

This process is essential to the functioning of the universe, allowing everything to continue expanding and ultimately sending the building blocks of the universe’s continued expansion.

In other words, everything in the universe is made of stardust, and it is supernovae that send this stardust to accumulate and create new things.

The remains of that star are still there, condensing to form a neutron star or black hole.

The study of supernovae has given scientists a wealth of information about the universe. Over time, the library of academic literature on supernovae has become even more extensive, especially as technological advances have helped scientists locate supernovae that occur in distant galaxies.

But there is still a big problem: how to predict whether a star will become a supernova?

Throughout our history, except for times when supernovae were visible in the skies above Earth in the distant past, scientists have not been able to determine in advance when a star will explode.

Of course, when a supernova actually happens, it becomes pretty obvious – after all, these explosions are literally shaping the universe. But all scientists can do is study the aftermath, seeing what the explosion left in its wake.

But Weizmann scientists managed to witness a supernova in real time. So how did they manage to do the impossible and predict whether a star would explode?

The answer is extremely simple: they didn’t.

In 2023, the researchers, part of Prof.’s group. Avishay Gal-Yam in the Weizmann Department of Particle Physics and Astrophysics hoped to use NASA’s Hubble Space Telescope for data on supernova interactions. Instead, they witnessed not only a supernova, but also one that was relatively nearby: a red supergiant in the neighboring galaxy Messier 101.

BUT THE old saying “Man plans, God laughs” could easily be rephrased as “Man plans, supernovas have bad timing”, because it came at a very inconvenient time.

The supernova was discovered on a Friday, which is already the weekend in Israel, and just before the weekend in Baltimore, where Hubble’s operations center is located. The person who found it was a Japanese amateur astronomer, Gal-Yam explained, noting that he was browsing his email while sitting at home that Friday. Seeing this, he promptly sent an email to his students.

To complicate matters further, this happened just before one of the study’s authors, doctoral student Erez Zimmerman, got married.

“I was about to get married on Sunday. I received a bunch of guests from abroad and we went to a bar together,” said Zimmerman. “A torrent of emails started arriving on my smartphone while I was still at the bar. I looked at the email and realized that this was exactly the supernova I was hoping to observe with the Hubble Space Telescope. This was a day and a half before the wedding… I went out to the car with my bride and told her, ‘Uh, look, I think there’s a supernova I need to work on.’ She said, ‘Hubble?’ And I said ‘Yes, Hubble’.”

Gal-Yam said: “It’s very rare as a scientist that you have to act so quickly. Most scientific projects don’t happen in the middle of the night, but the opportunity arose and we had no choice but to respond accordingly.”

This was a race against time, all the data needed to be obtained as quickly as possible, and they had to perfectly orient Hubble to the right location to collect the data before NASA’s Hubble operators left for the weekend.

Despite the horrible timing and Hubble’s own slowness, the researchers did the impossible. Within 50 hours, Hubble was observing the supernova – the first time scientists had gotten there so quickly.

But what about marriage? It still went ahead, and many of the researchers arrived a mix of exhausted and energized from all their work.

Zimmerman explained that he worked hard to get everything ready for the wedding day and then received confirmation from NASA that they would be observing the supernova. “So I knew this was going to happen the day after my wedding,” he noted.

Hubble even confirmed on social media that it was analyzing the supernova for Zimmerman.

So what did they learn?

Interestingly, Hubble had already observed and collected data from this specific part of the universe many times. As such, there was a huge amount of data available in the NASA archives.

Researchers were able to see the red supergiant star in its final days, creating an almost perfectly complete portrait of what a supernova is: the death of a star.

But remember: a supernova leaves something behind, usually a neutron star or a black hole. What about?

In this regard, the researchers noticed something interesting.

In a statement, Weizmann’s doctoral student Ido Irani noted that when calculating the density and mass of circumstellar material before and after the supernova, something was missing: specifically, a lot of mass.

Mass is not like weight, which can change with gravity. Instead, mass is a static figure. To disappear, it must have gone somewhere. The hypothesis put forward by the team is that a black hole formed and may have absorbed this mass.

But overall, researchers were able to witness a supernova like never before, which in turn means they are able, in retrospect, to study what a star was like in its final days, rather than resorting to what amounts to collection of one-star forensic evidence. Supernova.

Because that star was so close, the available data is of very high quality.

But there is still more to discover. The supernova is not over yet and new data is still coming in. Where will all the material go? What will this result in? Well, it was the materials spread by supernovae in the distant past that eventually created the Milky Way, our solar system, Earth and all life.

“There is a saying that we are all stardust, and it is true, actually, because every element of our body [originates] on a star,” Zimmerman said. “And when stars explode, they emit this material and eventually it ends up in us.”

Given all this, the possibilities could be practically endless.

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