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Dark comets are divided into two families

Dark comets are divided into two families

Dec. 10 () –

The discovery of seven new dark cometsa celestial object that looks like an asteroid but moves through space like a comet, has revealed that they are divided into two distinct populations.

Thus, the largest reside in the outer solar system and the smallest in the inner solar system, with several other characteristics that differentiate them. This discovery is published in the journal Proceedings of the National Academy of Sciences (PNAS).

Scientists had their first clue to the existence of dark comets when they noted in a March 2016 study that the trajectory of “asteroid” 2003 RM had moved very slightly from its expected orbit. That deviation could not be explained by the typical accelerations of asteroids, such as the small acceleration known as the Yarkovsky effect.

“When you see that kind of disturbance on a celestial object, it usually means it’s a comet, with volatile material outgassing from its surface, giving it a little boost,” he said. in a statement study co-author Davide Farnocchia of NASA’s Jet Propulsion Laboratory in Southern California. “But no matter how hard we tried, we couldn’t find any sign of a comet’s tail. It looked like any asteroid, just a point of light. So, for a short time, we had this strange celestial object that we couldn’t completely decipher“.

Farnocchia and the astronomical community didn’t have to wait long for another piece of the puzzle. The following year, in 2017, a NASA-sponsored telescope discovered the first documented celestial object in history that originated outside our solar system. 1I/2017 U1 (‘Oumuamua) not only appeared as a single point of light, like an asteroid, but rather its trajectory changed as if it were outgassing volatile material from its surface, like a comet.

“‘Oumuamua was surprising in a number of ways,” Farnocchia said. “The fact that the first object we discovered from interstellar space exhibited similar behaviors to 2003 RM made 2003 RM even more intriguing.”

By 2023, researchers had identified seven solar system objects that looked like asteroids but acted like comets. That was enough for the astronomical community to grant them their own category of celestial object: “dark comets.” Now, with the discovery of seven more of these objects, researchers could begin to address a new set of questions.

“We had a large enough number of dark comets that we started to wonder if there was something that set them apart,” said Darryl Seligman, a postdoctoral researcher in the physics department at Michigan State University, East Lansing, and lead author of the new paper. . “When analyzing reflectivity,” or albedo, “and orbits, we discovered that our solar system contains two different types of dark comets.”

The study’s authors found that one guy, whom they call outer dark comets, It has similar characteristics to comets of the Jupiter family: they have very eccentric (or elliptical) orbits and are larger (hundreds of meters or more in diameter).

The second group, inner dark cometsreside in the inner solar system (which includes Mercury, Venus, Earth, and Mars), travel in nearly circular orbits, and are smaller (tens of meters or less).

Like so many astronomical discoveries, Seligman and Farnocchia’s research not only expands our knowledge of dark comets, but also raises several additional questions: Where did dark comets originate? What causes its abnormal acceleration? Could they contain ice?

“Dark comets are a new potential source of having brought to Earth the materials necessary for the development of life“Seligman said. “The more we can learn about them, the better we can understand their role in the origin of our planet.”

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