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Astronomers spy on three comets that circle a star nearby

Artistic representation of exoplanets and comets in the orbit of Beta Poctoris
Photo: Michaela Pink

NASA's exoplanet hunting spaceship TESS has discovered three comets orbiting a starlight circle. Years away, so a new release.

Comets in our own solar system are solar orbiting objects that develop a cloud and tail from fleeting elements when they receive enough solar energy. Scientists have already discovered comet-like objects orbiting other stars, but these three are the first to be seen in Mission Transiting Exoplanet Survey Satellite (TESS) data. The findings show what exciting discoveries can be expected from this relatively new mission, which started in April 2018.

The first author of the study, master student Sebastian Zieba from the Austrian University of Innsbruck, analyzed TESS observations of Beta Pictoris, a well-known bright star in the southern sky. Scientists already knew this star is interesting – it has an exoplanet and a carbon-rich disc. However, the data revealed a strange break-in, a sign that something was passing in front of the star and darkening its light.

Beta Pictoris, however, may be hard to study, said Zieba's consultant Konstanze Zwintz. "The star itself is swinging," she explained. The light flickers and since there is a different light signal from the star, the researchers must fully understand it to detect the source of the dimming. Both the oscillating star and the darkening of the comet are incredibly weak.

"It's like being on a mountain, lighting a candle and going to another mountain, one kilometer away, watching the candle flicker," said Zwintz. "The signals … are even smaller than these."

After considering the flickering of the star and considering any potential sounds that TESS itself could cause, a signal like the capital letter V written in the font remained – a sharp fade, then a less sharp lightening. It looked exactly like a prediction made two decades ago of what Exokometen should look like, Zwintz explained. Upon closer examination of the data, they found two more of these signals, according to the study published in Astronomy and Astrophysics.

Other researchers also think it's cool. "It was a prediction made twenty (20) years ago that Beta Pictoris would have observable exocrats, so it's very satisfying to see that this is indeed the case," said Jessie Christiansen, astrophysicist at the Exoplanet Science Institute NASA in Caltech. Gizmodo said in an e-mail. "And the data is really clean, which helps with big claims like" exokomets. "

Of course, this is an interpretation of a data block, and more data is needed to better understand what's going on. It is unclear how much of what they see is the cometary nucleus and how much the tail is of gas and dust and how dense all that stuff is. Hopefully, researchers will someday be able to learn what these exokomets are made of.

The work continues to demonstrate the power of the TESS mission and the many exciting things it will find outside our solar system.

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