RZ Piscium may be smashing, eating its own planets

A new study shows that the blinking star RZ Piscium may be devouring the planets around it.
By Joseph Scalise | Dec 26, 2017
A team of U.S. astronomers analyzing the star RZ Piscium has found evidence that the body's random dimming episodes are the result of vast orbiting clouds of gas and dust created from one or more destroyed planets, according to research published inThe Astronomical Journal.

RZ Piscium sits 550 light years from Earth in the constellation Pisces. Sometimes, the star will go through dimming periods that can last as long as two days. During that time, the formation producesmore energy at infrared wavelengths than those emitted by stars like our sun. That suggests the body is surrounded by a disk of warm dust.

"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 lead author Kristina Punzi, a doctoral student at the Rochester Institute of Technology, according to Phys.org. "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."

Initially, astronomers concluded that RZ Piscium is a young sun-like star surrounded by a dense asteroid belt, where frequent collisions grind the rocks to dust. However, that evidence was far from clear. Further analysis showed the star was older than our sun, and it was just beginning to shift into the red giant stage. A dusky disk from the star's youth would have also dispersed after a few million years.

To explain that odd discrepancy,researchers used various telescopes to discover that, while the star is young, it is much too old to be surrounded by so much gas and dust. As most sun-like stars lose theirplanet-forming disks within a few million years of their birth, it is likelyRZ Piscium is destroying planets instead of building them.

Further ground-based observations showed thatthe dust is accompanied by substantial amounts of gas. That discovery, combined with the intense heat of the dust, means the debris likely orbits roughly30 million miles from the star.

"While we think the bulk of this debris is about as close to the star as the planet Mercury ever gets to our Sun, the measurements also show variable and rapidly moving emission and absorption from hydrogen-rich gas," said study co-author Carl Melis, an associate research scientist at the University of California, San Diego, in a statement. "Our measurements provide evidence that material is both falling inward toward the star and also flowing outward."

Though astronomers are not sure, they think RZ Piscium's tides are stripping material from a close substellar companion or giant planet in order to produce the ring of gas. There is also a chance thatone or more massive gas-rich planets in the system underwent a catastrophic collision in the recent past.

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