Astronomers See a Star Eating a Planet for the First Time

(Daily Beast, May 4, 2023)

Our own humble star, the sun, will soon die out. As it does, it will grow in size and engulf the planets around it, destroying them in the process. Scientists have seen stars bump into each other, but for the first time, they have recorded how this type of old star expansion actually ate up a planet. It was specifically a gas giant planet like Jupiter, nearly 10 times bigger, though.

The article in The Daily Beast referenced the original scientific journal article, An infrared transient from a star engulfing a planet, which was found in Nature.

A "transient" is a short event. Scientists used data collected by the Zwicky Transient Facility (ZTF) in California to discover a star eating a planet. The ZTF detects transients in visible and infrared (IR) wavelengths with a special camera on a telescope at the Palomar Observatory. The brief changes in light can mean several things, but this time it pleasantly surprised the scientists. They had seen stars eat stars before and generate bright transients as it happened, but this time the data showed a weaker optical change, so they determined the star had eaten something smaller: a planet.

Just to show how patient astronomers have to be, they noticed a mild rise in IR light coming from the system for 7 months, and then it rose more strongly in just 10 days to its peak. After that, they continued to monitor the IR transient for 15 more months!

Let's use a simple analogy on a much shorter time scale to picture this transient. Imagine, if you will, tossing a small piece of paper onto hot coals. The heat will burn the scrap quickly, but not too quickly for you to see how it gets dark with heat, flames up, and then chars and remains on the coals for a short time after that. Measuring those changes in space is what the researchers did for this transient called ZTF SLRN-2020. Of course, they used other data to confirm their findings, but the IR details are probably easier to understand.

Astronomy magazine has also just published an article New simulations zoom in on planets swallowed by their stars, which shows results from The Astrophysical Journal. The results are shown as some cool animations of the hydrodynamical flow of gases surrounding a star as it theoretically engulfs a planet.

FUN BONUS STUFF: Here's a YouTube video (3:31) with Neil deGrasse Tyson explaining how science discovered IR and ultraviolet light.