This image shows how the stars KIC 3542116 watching the Kepler space telescope. Cooler colors in darker regions, and warmer colors brighter regions.
There are small comets in orbit around foreign suns. And the man can detect.
Six times, about 800 years ago, dark things passed between the bright-yellow dwarf star KIC 3542116 and Earth. They were small in cosmic terms, about 330 billion tonnes (300 billion tons). That is about the size of Halley’s Comet, or just a one-245-millionth of the mass of the Earth to the moon.
But they were large enough. They blocked a fraction of a fraction of the light that was streaming out of that star. Eight hundred years later, the sensitive lens of the Kepler Space Telescope — an almost meterwide piece of precision-ground glass floating in the darkness of the space detects that dimming as KIC 3542116 the old light reached this solar system. [The 9 Most Brilliant Comets Ever Seen]
The stars seemed to dim rapidly, though almost imperceptibly, as the small dark things passed on the front side (from Earth perspective) six times between 2009 and 2013. Three times the gray deep, and three times the dimmed light, at irregular periods, during that four years.
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This is a well-known signal-to astronomers, the same type of dimming that has allowed them to spot the majority of the 3,728 planets discovered by February. 2. But the little dark things behaved as small planets only at the beginning of their journey. As they continued their journey across the plane of their star, the star only its brightness slowly, in the course of about a day.
That is not how exoplanets (in principle, large symmetrical bulbs) look at Kepler. But it is how a comet, with its long dusty tail, would appear. In fact, it’s how a team of astronomers predicted that such a comet passers-by would look in 1999.
In a study due for publication Feb. 21 in the journal Monthly Notices of the Royal Astronomical Society (and for the first time released in 2017 on the arXiv), a team of researchers report that these dark objects are the first “exocomets, or comets in another galaxy, that has ever been discovered.
The team wrote that they are not exactly how many comets were there, cast a shadow over Kepler’s lens during that period. It may be six persons, each one close to pass to their star that showed up in Kepler’s data. Or there is a smaller cluster, with some comets make multiple crossings.
Maybe just a comet was in orbit around the star very tight, they suggest — but they were not able to fully figure out the trajectory of a single comet that would have been for the six irregular time shadows.
The astronomers for more than five months of hunting by more than 201,250 Kepler photos before they found these six transits, and in all that time they found only one other likely comet’s shadow crossing over of another star. KIC 11084727, also a yellow dwarf, gray times, vaguely, like KIC 3542116 where the six shadows were found.
Two stars “in the vicinity of a pair of twins,” the astronomers wrote. Both are very light, and of similar size and scope. And they are somewhat unusual in the Kepler dataset, they wrote, that tends to target “cooler, sun-like stars.” Perhaps, they suggested, comets (or at least comet transits visible from the Earth) are more frequent around stars of this type.
Regardless of where more might be found in the future, these comets are the smallest objects that humans have ever observed in alien solar systems. Previously, the authors, the smallest thing ever spotted in the passage of the star Kepler-37b. That small exoplanet is just 2,400 miles (3,860 kilometers wide, or a little larger than the moon.
Originally published on Live Science.