Someday the Sun will swell and swallow up neighboring planets, including our own. In the meantime, scientists have seen this process from a safe distance, seeing for the first time how a massive planet dies in the embrace of its star.
At the end of their lives, medium-sized stars greatly increase in size, briefly turning into dim red giants. In about five billion years, this will be the fate of our Sun, which will expand, cool down, and swallow up the nearest planets, including Earth. Recently, astronomers have seen this process "live", watching as a star located 12 thousand light-years away destroyed a massive planet.
Kishalay De of the Massachusetts Institute of Technology (MIT) and colleagues analyzed data from the Palomar Observatory's Zwicky Transient Facility survey. Their main goal was to look for bright red novae - explosions caused by star mergers. Scientists noticed a similar signal in the 2020 observations: it came from a distance of more than 12 thousand light-years and was named ZTF SLRN-2020.
Within ten days, ZTF SLRN-2020 became a hundred times brighter, but still not bright enough for merging stars. So scientists took a closer look at the source, using instruments from NASA's NEOWISE Space Infrared Observatory and the ground-based Keck Observatory. The new data showed that the energy of the flare was quite modest, about a thousand times less than one would expect from a red nova. And instead of a cloud of red-hot plasma, it was surrounded by slightly heated dust, poor in both hydrogen and helium.
Scientists concluded that the distant event was due to the merger of not so large objects. After additional observations and calculations, they showed that ZTF SLRN-2020 began blazing in the infrared long before it was detected and remains bright until now. "Whatever merged with the star was a thousand times smaller than the star. By happy coincidence, Jupiter's mass is about a thousand times less than the Sun. So we realized: this is a planet falling on the star," noted Kishalai De.
The star itself is only in the early stages of becoming a red giant, but a nearby planet has already "not done well. The outer shell of the star quickly reached its orbit, and due to the friction of this substance, the planet, weighing about 30 times more than Earth, began to slow down and decline. As it heated up more and more and lost matter, it created an infrared signal until it finally collapsed, creating a visible flash in the optical range.
