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spaceSpace and Physics

Mysterious Dimming Star May Have A Giant Cloud Of Material Orbiting It

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Jonathan O'Callaghan

Senior Staff Writer

clockDec 19 2016, 17:02 UTC

simonekesh/Shutterstock

Astronomers have found a strange star that is dimming in a peculiar way, indicating it may have a large cloud of material orbiting it.

The star is called RIK-210, and it is located 472 light-years from Earth. A team of researchers led by the California Institute of technology (Caltech) used data from NASA’s Kepler telescope to study the object, which was observed between August 22 and November 11, 2014, during its K2 mission. Their research is available in a paper on arXiv.

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The team observed that the star dimmed for between 6 and 18 hours every 5.67 days, in time with its rotation. These dips in light were between 5 and 20 percent of the star’s total light – far larger than would be expected from a planet in orbit.

RIK-210 is only 5 to 10 million years old, half as massive as the Sun, and is about 1.24 times the size of the Sun. Dimming events like this have been seen before, but normally around stars with a planet-forming disk of material, which RIK-210 does not appear to have.

What’s more, the dimming effect does not seem to have occurred before or after the K2 observations, based on data from other telescopes, suggesting it only happened for a short period of time.

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"We find transient, transit-like dimming events within the K2 time series photometry of the young star RIK-210,” the scientists wrote in their paper. “These dimming events are variable in depth, duration, and morphology.”

The dips were seen every 5.6685 days. David et al, 2016

To explain what’s going on, they’ve ruled out a couple of options, namely another large object (like another star or a brown dwarf) eclipsing the star from our point of view, because they could not see any gravitational effects from such objects. They also ruled out features on the surface of the star, such as sunspots, being the cause.

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Instead, they suggest that a large cloud of material may be orbiting the star. There are a number of possible progenitors for this cloud, including the remnants of a late stage of planetary formation, debris left from a collision, or even a protoplanet surrounded by dust or gas with an elongated tail.

“Speculative sources of the obscuring material could be a magnetospheric cloud, an accretion flow from residual (yet undetected) gas and dust, remnants of the late stages of planet formation, the product of a giant-impact type collision, an enshrouded protoplanet with an extended tail, or one or more eccentric bodies undergoing periodic tidal disruption upon each periastron passage,” the researchers wrote.

They are now hoping for further studies of the stars, including more transit observations and also observing its emitted light, to fully understand what’s going on.


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