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The bizarre comet from another star system just noticed

During the sleepy hours of August 30, a Ukrainian amateur astronomer named Gennady Borisov saw a strange comet zooming through our solar system. Now astronomers have tentatively verified that the object, named C / 2019 Q4 (Borisov), is moving too fast for it to be captured by the gravity of the sun – a sign that it is probably an interstellar interloper.

If these results continue to hold, C / 2019 Q4 would be just the second visitor from another star system ever discovered, following the 2017 discovery of the enigmatic space rock known as & # 39; Oumuamua. Although its origin is not yet entirely certain, C / 201

9 Q4 is a confirmed comet. Already, astronomers have discovered that the object – which is probably a few miles across – has a coma, the fuzzy mantle of dust and gas that forms when sunlight warms a comet's icy surface.

This means that researchers will be able to gather much more information about its composition than they could for & # 39; Oumuamua. For one, the C / 2019 Q4 is larger and brighter, giving more opportunities to study its light and tease out chemical clues. In addition, astronomers & # 39; discovered Oumuamua just on their way out of the solar system – but C / 2019 Q4 is still incoming. It will approach the sun on December 7 and it will be closest to Earth, within 180 million miles, on December 29.

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"This is the first very active object we have seen coming in from something formed around another star," says Michele Bannister, an astronomer at Queen's University Belfast. Bannister adds that observations of C / 2019 Q4 cannot be taken seriously until mid-October, due to its position relative to the blinding sun. But then, for months to come, astronomers will turn their eyes to get what may be their best appearance yet on an interstellar visitor.

"What is really amazing is that this thing should be observable for a year," said Matthew Holman, interim chief of the International Astronomical Union & # 39; s Minor Planet Center, which issued the verification of C / 2019 Q4's path through space Wednesday evening.

"We get to see a little bit of another solar system," he adds, "and without necessarily knowing which one it came from, it is exciting."

Very eccentric

Borisov, a veteran cage hunter, found C / 2019 Q4 by focusing their observations at the Crimean Astrophysical Observatory on the low horizon to the northeast, in a sky patch near the constellation Gemini, astronomers tend to avoid peeking into these "light" patches of sky near the horizon, as they are difficult to see in and can damage the telescope's sensitive optics.

Early reports on Borisov's discovery made waves among astronomers Quanzhi Ye at the University of Maryland first learned about the comet on Sunday, after a colleague commented on the object's bizarre trajectories in a group message. also noted that Scout, a comet and asteroid tracking service operated by NASA's Jet Propulsion Laboratory, continued to calculate that the object did not appear to have a circular or elliptical orbit.

Ye was particularly fascinated by one of the comet's orbital parameters: its eccentricity. If a path's eccentricity is zero, the object traces a perfect circle around its home star. The more elongated and narrow the trajectory, the closer the eccentricity comes to one. If an object in our solar system has an eccentricity greater than one, it means that the object has an arcuate path and visits once. The Minor Planet Center says that C / 2019 Q4's eccentricity exceeds three.

According to Ye, it is unlikely that C / 2019 Q4 was a comet formed on the edge of the solar system and in some way tangled into an escape path. To get this kind of jerk, a comet would need to get close to an object large enough to change its course, like a planet. But as far as astronomers know, Q / 2019 Q4 could not have come anywhere near such usurpers in our solar system. The orbits of the planet around the sun are more or less in line with the same plane, but C / 2019 Q4 seems to dive bomb the solar system at a 44-degree angle.

"That's why we say gravitational interference is almost impossible," Ye says.

Telescope time

Astronomers estimate that at a given time there is an interstellar comet or asteroid somewhere within the orbit of Mars, and 10,000 or so within Neptune's orbit – but these objects are small and extremely faint, making them almost impossible to see.

& # 39; Oumuamua, the first interstellar visitor discovered in our solar system, rocket again in the fall of 2017. Astronomers did not detect the strange object until it was on its way out of the solar system, damaging it at 98,000 miles per hour, but in the small amount of time they had, avid scientists around the world turned their telescopes toward the object, and they learned a surprising amount about this paragraph. cosmic debris. (Learn more about & # 39; Oumuamua and what made it so strange.)

While the distant object just looked like a pin of light in the best of telescopes, it indicates that the intense darker and brighter each other for a few hours that it was elongated, rolling end ends as it zips through our solar system. Astronomers estimate that the object was somewhere between 590 feet and a quarter of a mile long but only up to 130 feet wide, giving the rocky body a pencil-like appearance.

Even more curious, "Oumuamua did not continue to compete at the same pace. After throwing around the sun in early 2018, it unexpectedly rushed up. Speculation immediately swirled about the cause. Harvard professors Shmuel Bialy and Abraham Loeb presented Another secular idea: Maybe it was a spaceship that used a sun sail sent by a foreign civilization.

However, there is almost certainly a more mundane explanation. According to other research, ventilation openings on the object's surface could have released gas jets that gave it a boost , in a spread of cometary activity too weak for our telescopes to see. Or, "Oumuamua could have been a lump of porous ice that was light enough to just give it sunlight a nudge.

"Oumuamua left many mysteries in its wake that can never be solved, so the prospect of studying C / Q4's even more detail has attracted astronomers. When asked via email what he did from Minor Planet Center's verification, Ye: "Yeaaaaaaaaaah time to take the telescope !!!"

Maya Wei-Haas contributed to the reporting.

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