Astronomers discover more dark comets

The first dark comet (an object that looks like an asteroid but moves through space like a comet) was reported less than two years ago. Six more were discovered soon after. In a new paper, researchers announce the discovery of seven more dark comets, doubling the number of known dark comets and finding that they fall into two distinct populations. One is the larger comets that exist outside the solar system, and the other is the smaller comets that exist inside the solar system. Various other characteristics that make them stand out.

The findings were published in the Proceedings of the National Academy of Sciences on Monday, December 9th.

Scientists first became aware of the existence of dark comets in March 2016, when they noticed that the orbit of the asteroid 2003 RM was slightly deviated from its expected orbit. This deviation cannot be explained by typical accelerations of asteroids, such as the small acceleration known as the Yarkovsky effect.

“When you see such perturbations in a celestial object, it usually means it’s a comet and volatiles are ejecting gas from its surface, giving it a little thrust.” said 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 the comet’s tail. It looked like any other asteroid. It was just a point of light. So for a while, we couldn’t find any sign of the comet’s tail. There was this strange celestial body that we couldn’t find.”We don’t know completely. ”

strange celestial body

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-ever documented celestial object that originated outside our solar system. 1I/2017 U1 (Oumuamua) not only appeared as a single point of light like an asteroid, but also changed its orbit as if it was emitting volatile substances from its surface like a comet.

“’Oumuamua was surprising in several ways,” Farnocchia said. “The fact that the first object discovered from interstellar space to behave similarly to 2003 RM makes 2003 RM even more surprising. It became interesting.”

By 2023, researchers have identified seven solar system objects that look like asteroids but behave like comets. That was enough for the astronomical community to give it its own celestial category: “dark comet.” Now, the discovery of seven more of these objects allows researchers to address a new set of questions.

“There were enough dark comets that we could start asking if there was something that differentiated them,” said Dr. Schwarzenegger, a postdoctoral fellow in the Department of Physics at Michigan State University and lead author of the paper. said one Darryl Seligman. new paper. “By analyzing their reflectance, or albedo, and their orbits, we found that our solar system contains two different types of dark comets.”

Two types of dark comets

The study’s authors found that a class of comets called outer dark comets have characteristics similar to Jupiter-based comets. They have highly eccentric (or elliptical) orbits and are on the larger side (more than a few hundred meters in diameter).

The second group, inner dark comets, reside in the inner Solar System (including Mercury, Venus, Earth, and Mars), orbit in roughly circular orbits, and are smaller in size (less than a few tens of meters).

Like many astronomical discoveries, Seligman and Farnocchia’s work not only expands our knowledge about dark comets, but also raises some additional questions. Where do dark comets come from? What causes their unusual acceleration? Is it possible that there is ice in it?

“Dark comets represent a new potential source of materials needed for the development of life on Earth,” Seligman said. “The more we learn about them, the more we will understand their role in the origin of our planet.”