Fatal Attraction

Star swallows its planet: new discovery by NASA's James Webb Space Telescope

A planet the size of Jupiter about 12,000 light years from Earth, having reduced its orbit, was drawn towards the star and was eventually sucked into it

23 April 2025

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A new, important clue as to how the planets of the solar systems in our Galaxy end up, sooner or later. This is yet another excellent result from NASA's James Webb Space Telescope, which has added a new chapter to this subject that concerns us all: a star has been observed for the first time as it literally swallows up one of its planets, thanks to the force of gravity it exerts. The new findings suggest that the star did not actually swell up to encompass a planet, as previously assumed: instead, observations from the James Webb Space Telescope show that the planet's orbit shrank over time, slowly bringing it closer to its parent star until it was completely swallowed up.

The star we put in the centre of the stage is about 12,000 light years from Earth, close enough to us, then, but not too close, since the linear size of our Galaxy is estimated at about 106,000 light years

Already in 2023, astrophysicists, using an instrument in the famous Mount Palomar Observatory, had observed an important flare, a flash of light in the optical field, that of the wavelengths we normally see with our eyes.

This type of event is given a name, and that was called, ZTF SLRN-2020. Going to look up what another NASA satellite, NEOWISE, had recorded of this flash, the researchers saw that the star had indeed lit up in the infrared well over a year before the flash of optical light, probably due to the presence of dust around the star itself, which can be seen very well when looking in the infrared.

Star Expansion

Nothing special in the preliminary conclusions of 2023: we know that stars such as our Sun, after a long stay in a state of equilibrium, such as the one we are currently experiencing, due to complicated issues related to the nuclear fusion that takes place within them, expand a lot. In the case of our solar system, calculations, based on what has been observed in other similar stars, predict that our Sun will invade the space of the nearest planets. In our case it will expand to encompass Mercury, Venus, our Earth and Mars, almost up to Jupiter, about 500 million kilometres if we want to attempt a number and consider that we are at 150 million.

(NASA)

It expands a lot, therefore, and even if, as a consequence, matter is, of course, rarefied, since it has to fill a much larger volume, we will certainly not fare well on Earth. However, there is no need to worry too much: if the astrophysicists' calculations are correct, this will certainly happen, but in four billion years or more.

The first hypotheses for interpreting the ZTF flash SLRN-2020 were therefore directed towards this hypothesis, which was considered normal.

This is where Nasa's James Webb Space Telescope, with a major European participation, comes into the picture.

The fallen planet inside the star

Thanks to the high sensitivity of an instrument on board the space telescope, the Miri spectrograph, Webb was able to accurately measure the star's hidden emission and found that the star was less luminous than expected if it had expanded as the red giant star theory assumes. The twist, therefore, indicates that the planet had not been engulfed, or cannibalised if you like the 'crime' genre, but had probably been drawn towards the star and eventually fallen into it.

The planet was the size of Jupiter, large therefore, as it occupies a volume 1320 times that of the Earth, and orbited very close to its star, probably less than 50 million kilometres, less than Mercury does to our Sun. Over millions of years, the planet, due to gravitational attraction, orbited closer and closer to the star, leading to catastrophic consequences.

"Eventually, the planet began to skim the star's atmosphere. From that point on, an uncontrolled and faster falling process began," said Morgan MacLeod, a member of the Harvard-Smithsonian Center for Astrophysics and Massachusetts Institute of Technology group in Cambridge, Massachusetts. "The planet, as it fell, began to break apart around the star."

In the end, the planet would have literally dissolved, even ejecting gas from the outer layers of the star, which then cooled around the star itself, thus fully justifying the observations made.

A case of fatal attraction then.