Astronomers think the erratic dimming of a distant star may be caused by the orbiting remains of planets it has “consumed”.
Stars normally shine brightly and consistently, but RZ Piscium – found 550 light years away in the constellation Pisces – is prone to unpredictable and previously unexplained periods of dimming.
“Our observations show there are massive blobs of dust and gas that occasionally block the star’s light and are probably spiralling into it,” said Kristina Punzi, a doctoral student at the Rochester Institute of Technology and lead author of the new study.
The scientists think these orbiting clouds result from the star – dubbed an “eater of worlds” by Indiana University, which was also involved in the study – destroying planets in its orbit.
“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,” said Ms Punzi.
Planets that are ripped apart by their suns in this way are known as “disrupted planets”.
“It seems either that we’re seeing a fairly massive, gaseous planet being pulled apart by the star, or perhaps two gas-rich planets that have collided and been torn apart,” said Professor Catherine Pilachowski, an astronomer at Indiana University and one of the study’s co-authors.
This behaviour has been outlined in a new study published in The Astronomical Journal.
An alternative explanation for the sun’s dusty surroundings could be that it is relatively young.
Younger stars can possess “planet-forming discs” of dust, but these tend to disperse after a few million years.
Astronomers can use lithium to age stars because the element declines over time. Analysis of lithium on the star’s surface suggested RZ Piscium is around 40 million years old, signifying its belt of debris was not a mark of youth but newly acquired.
This led Ms Punzi and her collaborators to conclude that the star was consuming its planetary “offspring”.
The work provides an insight into the machinations of solar systems, which can often be unstable – particularly in their early history.
Newly born planets strongly interact with each other and with their suns through gravity, leading to events similar to the destructive nature seen on RZ Piscium.
However, after longer periods of time, solar systems do tend to stabilise as ours has.
“This discovery really gives us a rare and beautiful glimpse into what happens to many newly formed planets that don’t survive the early dynamical chaos of young solar systems,” said Professor Pilachowski.
“It helps us understand why some young solar systems survive – and some don’t.”
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