Caught in the Act: Astronomers Spot Star Swallowing a Planet for First Time

upstart writes:

A sneak peek at Earth's eventual fate:

Roughly 5 billion years from now, our Sun will end, not with a bang but with a whimper. That's when it finally burns through all the fuel in its core and puffs outward into a red giant, swallowing all the inner planets of our Solar System in the process, including Earth. But no star has ever been caught in the act of gulping down a planet this way-until now. Astronomers have spotted a white-hot flash from a distant star in our Milky Way galaxy and concluded that it came from the final stage of this process, according to a new paper published in the journal Nature. Yes, it's a literal "Death Star," announced on the eve of Star Wars Day (May 4).

[...] This process only occurs a few times a year in the Milky Way. Astronomers have observed the early stages of the process (planets so close to their host stars that they will inevitably be engulfed when those stars expand) along with the aftermath of this stellar evolution (when the stars have puffed up and seem to have peculiar properties, such as their rotational speed or chemical composition). But scientists have never witnessed the actual devouring. That's what makes this discovery so exciting, according to co-author Kishalay De, an MIT postdoc: This is the first direct evidence of a crucial stage of stellar evolution.

[...] De was poring over data from the Zwicky Transit Facility (ZTF) at the Palomar Observatory in California about three years ago, hunting for the telltale brightening (by a factor of a few thousand times over the course of a week) that marks a nova. Such explosions occur when a white dwarf steals matter from a companion star. De spotted a star brightening by a factor of a few hundred times over the course of a couple of weeks. He quickly checked out observations of the same star taken by the Keck Observatory in Hawaii. But the spectrum revealed that the composition and temperature of the gas surrounding this star was nothing like a nova. "This source appeared to be surrounded by a bunch of cold gas," De said. "We were seeing signs of molecules that can only exist at cold temperatures."

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