Scientists have found a star, "eating" the planet

Christopher Davidson
July 23, 2018

Trying to resolve the mystery of RW Aur A, the scientists used data gathered by NASA's Chandra X-ray Observatory, which provided them with evidence that the stars' light is being sucked up by a mysterious "absorber" that "inhabits" the inner disk of the star.

Inquiry about this star spread as it commenced to dim extremely habitually and for lengthier periods of time as per Hans Moritz Guenther, a research scientist in MIT's Kavli Institute for Astrophysics and Space Research and lead author on the study. The scientists believe that at least one of the planets sucked by RW Aur A contained a very high level of iron, releasing it into the star's disk after the collision.

The study proposes that the parent star, situated around 450 light-years from the Earth, at present is in the course of gulping down the planetary remains resulting from the blast of young planetary bodies. This discovery gives insight into the processes affecting the survival of infant planets.

The scientists have always been fascinated by a binary star system called RW Aur, belonging to the Auriga constellation and located some 450 light years away from us. Every few decades, the star's light has faded briefly before brightening again. Fragments of these bodies would fall on this star, a phenomenon predicted but never observed for a young sun a few million years old. If one or both of those doomed worlds were made partly of iron, the collision could release large amounts of iron-rich debris that could obscure the RW Aur A's light as it plunged into the star.

The star's previous dimming events may have been caused by similar collisions of planet-size bodies or large remnants produced in previous collisions.

RW Aur A dimmed again in January 2017 and this time around, Guenther's team studied the event with Chandra.

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"If our interpretation of the data is correct, this would be the first time that we directly observe a young star devouring a planet or planets", Guenther said.

Around young stars, usually has a disk of matter from fine dust to large objects, which disappears in 5-10 million years of the star. This star and its binary companion star, RW Aur B, are both about the same mass as the sun.

The noticeable dips in the optical brightness of RW Aur A that occurred every few decades each lasted for about a month. The decrease in luminosity was then repeated in mid-2014 and it was not until November 2016 that the star became "normal" again. This would explain the sudden iron enrichment of the protoplanetary disk and the crown of the star. If the disk's structure changes suddenly, such as when the star's partner star passes close by, the resulting tidal forces can release the trapped particles, creating an excess of iron that can fall into the star.

The study is in Wednesday's Astronomical Journal.

Regardless, Guenther hopes to continue making observations of the star.

"Here, we see a lot more iron, at least a factor of 10 times more than before, which is very unusual, because typically stars that are active and hot have less iron than others, whereas this one has more", Guenther says.

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