2023-05-10 18:00:21
Twice in less than six months, the ZTF has been talked about in the prestigious magazine Nature. Behind this acronym hides a camera, Zwicky Transient Facility, installed on one of the telescopes of Mount Palomar (California), which scans the sky with a fairly wide field of view, looking for what astronomers call transient events (passages of comets or asteroids, but also star explosions…). On November 30, 2022, it was announced that the ZTF had detected a star shredded by a black hole. This time, in its May 4 issue, Nature publishes an American study showing another cosmic event as brutal as it is unprecedented: the absorption of a giant planet by its star.
It all started in May 2020. The paper’s first author, Massachusetts Institute of Technology postdoc Kishalay De, was reviewing ZTF data for bright flares in double star systems. ” A night, he says, I noticed that the brightness of a star had increased by a factor of 100 in the space of a week, without warning. I had never seen such a stellar puff in my life. » What was going on up there?
To find out, Kishalay De and several fellow astrophysicists collected additional data from other instruments to see what happened before and after the sudden brightening. And they proceeded by elimination. The first reflex of an astrophysicist faced with such a phenomenon is to think of a classic nova. Imagine a moribund double star, one component of which is a red giant at the end of its life and the other a white dwarf, a kind of stellar corpse that is still hot and extremely dense. The latter tears material from its companion, which “piles up” on its surface, until all this accumulated gas produces a thermonuclear explosion. And a nice flash.
A red nova
The authors of the study had to rule out this scenario, because the data collected did not stick. The May 2020 phenomenon did not give rise to a fantastic and brief expulsion of very hot gas. On the contrary, for months after the luminous burst, it was noted that the star regularly released rather cold material into space, clearly visible in the infrared. Researchers then turned to a lesser known – and also calmer – type of nova, the red nova, which signals the merger of two stars.
But there again there was a catch. By resuming the measurements of the original event, Kishalay De and his associates noticed that the quantity of energy emitted was ridiculously low compared to what it should have been if one star had absorbed another. About a thousand times weaker. What had been “gobbled up” must therefore have been a thousand times less massive than a star. However, when we know that, in our Solar System, the most imposing of the planets, the gaseous giant Jupiter, has a mass almost exactly one thousandth of the mass of the Sun, the conclusion was not complicated to find: what the ZTF had observed, 12,000 light-years from Earth, was the absorption of a giant planet by its star.
You have 30.26% of this article left to read. The following is for subscribers only.
#star #caught #act #absorbing #planet