spaceSpace and Physics

This Mysterious Dimming Star Might Be Eating Its Ruined Planets


Jonathan O'Callaghan

Senior Staff Writer

RZ Piscium appears to be surrounded by clouds of debris. NASA’s Goddard Space Flight Center/CI Lab

There's more than just one dimming star in town. Astronomers have discovered that the remains of planets may be causing another distant star to dim unpredictably.

The star is called RZ Piscium, and it’s located about 550 light-years from Earth. Observing the star, it was found that it could become up to 10 percent fainter now and again, for a long as two days.


The were two possible theories for why this was so. One idea was that the star, about 1 percent the age of our Sun, was surrounded by a dense asteroid belt. Frequent collisions would create a disk of debris, dimming the star.

Another idea was that it was actually older than our Sun, and was becoming a red giant. As a result it would be destroying planets as it expanded, producing dust and dimming its light.

The answer, according to a paper published in The Astronomical Journal, seems to be a bit of both. RZ Piscium does indeed seem to be young, but it also appears to be devouring some of its planets. And that’s causing a cloud of debris to periodically reduce its brightness from our point of view.

"Our observations show there are massive blobs of dust and gas that occasionally block the star's light and are probably spiraling into it," said Kristina Punzi from the Rochester Institute of Technology (RIT) in New York, lead author of the study, in a statement.


"Although there could be other explanations, we suggest this material may have been produced by the break-up of massive orbiting bodies near the star."

According to the study, it looks like the star is stripping material from a giant planet in orbit, producing streams of gas and dust. The planet might also be already destroyed, or it may be that multiple planets have collided in the system. At any rate, planets seem to be involved.

Scientists monitored RZ Piscium using a variety of telescopes to observe its light, noting that it produced far more infrared light than other wavelengths. This indicated it as surrounded by a warm disk of dust.

Its X-ray output was also found to be 1,000 times greater than our Sun, a sign that this star is young and not old. Lithium measurements also showed that it was likely about 30 to 50 million years old.


This is too old to be surrounded by the star’s original planet-forming disk of debris, so the astronomers surmised that it must be destroying its existing planets, not building new ones. And that led them to the conclusion that this star is surrounded by material from some ruined planets, either destroyed by the star itself or each other.


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