This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Like Earth, most planetary bodies circle their star in stable, detached orbits. These companionable systems can suddenly change when a planet comes too close to its star.
In such a close encounter, a star can pull the planet in and swallow it whole. Across the galaxy, astronomers have seen plenty of stable, detached planetary systems. They have also observed a handful of stars quickly engulfing their planets.
Now, for the first time, scientists have spotted a system that is striking a curious balance between the two extremes. And it's revealing a new way that stars can interact with planetary companions. In a paper appearing today in Nature Astronomy, scientists at MIT and elsewhere have discovered a star leisurely snacking on a closely orbiting brown dwarf—a planet-like object that is more massive than a planet yet not quite as big as a star.
The new system, named ZTF J0440+2325, is within the Milky Way galaxy, roughly 300 light-years from Earth, and represents the first observation of a low-mass object that is slowly and steadily consuming material from another low-mass object. The rate at which the star is feeding from the brown dwarf suggests that this slow stellar cannibalism could carry on for hundreds of thousands or even billions of years. "When we think of stars interacting with planets or brown dwarfs, the picture is always that the star eventually swallows the other thing," says Kevin Burdge, assistant professor of physics at MIT.
"This is what will happen to the Earth when the sun becomes a red giant. But here, we've found an alternative: Instead of swallowing the thing up, the star can gradually eat it, for billions of years." The study's MIT coauthors include Aaron Householder, Kaitlyn Shin, Saul Rappaport, Joheen Chakraborty and Emma Chickles, along with collaborators from Caltech, the University of Hawaii, the Instituto de Astrofísica de Canarias and the Universidad de La Laguna in Spain, and the Harvard and Smithsonian Center for Astrophysics. The new system was spotted initially by the Zwicky Transient Facility.
The ZTF uses a camera as part of a telescope at the Palomar Observatory in California to scan the sky for rapid changes in brightness, which could signal the presence of a supernova, a gamma-ray burst or colliding neutron stars. Several years ago, Burdge was looking through ZTF data when he noticed a strange light curve, or pattern in brightness. Light curves for supernovas resemble a bell curve, signaling the gradual brightening and then fading of a star as it bursts.
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