2023-05-03 15:41:02
The planets that orbit very close to their star just before being engulfed, astronomers no longer count them. Neither do the giant stars that have made their planets their last meal. But this time, they saw something they had never seen before. A star swallowing a planet. Live.
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[EN VIDÉO] When and how will the Sun die? Our star would be halfway through its life, but what will happen…
In four to five billion years, our Sun will run out of fuel. Like all stars of its kind, it will then become extremely bright, and begin to grow in size. Again and again. To transform into what astronomers call a red giant. Along the way, our Sun will have literally swallowed up, one by one – at least the closest ones – the planets that have been gravitating around it for so long. Among them, our Earth.
It is exactly this film which took place before the astonished eyes of researchers of Massachusetts Institue of Technology (MIT, USA), Harvard University (USA), Caltech (USA) and other prestigious universities. Some 12,000 light-years from our Solar System, on the side of the constellation of the Eagle, in May 2020. As they searched for binary systems of stars that would suck up the mass of the other, the astronomers observed a star becoming more than 100 times brighter than usual in just 10 days before quickly fading away. According to the researchers, it was unlike anything they had seen so far.
But it was by analyzing the spectroscopic measurements taken by the Keck Observatory (Hawaii) that the researchers had the real surprise. Instead of detecting the helium and hydrogen they expected to see, they recorded signs of “particular molecules”. Molecules that only exist at very low temperatures. Incompatible with what usually happens in a binary system.
Elements that betray the event
A year later, when astronomers observed the same region using an infrared instrument from the Palomar Observatory (USA), they are “fallen out of their chairs”. Because the initial source was then “incredibly bright in the near infrared”. The signature of the presence of cold materials. Perhaps a clue to point them towards a star merger event, ultimately, rather than an explosion.
To be convinced, the researchers then compiled this data with others, returned by the Neowise space telescope. They were thus able to calculate the amount of energy released by the star since the initial event. The result they found was about 1/1,000 of what they expected for a stellar fusion event. Conclusion: what crashed into the star in question must have been about one thousandth the mass of a star. A bit like… Jupiter!
This is how astronomers today are able to tell us the story of what they have observed in the sky since May 2020. “brilliant hot flash” doubtless corresponding to the last moments of a Jupiter-like planet drawn towards the atmosphere of its dying star. As the planet fell onto the star’s core, the star’s outer layers exploded. They then settled into cold dust over the next year.
On numerous occasions, researchers had already observed the before and after of the death of a planet. This is the first time they have witnessed these last moments in real time. A discovery that they unanimously qualify as “really exciting”.
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