NASA discovers seven objects that look like asteroids but act like comets

NASA has taken to its Jet Propulsion Laboratory (JPL) blog to announce the official discovery of seven strange celestial objects, with the findings being published on Monday, December 9, in the Proceedings of the National Academy of Sciences.

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An artistic illustration of 'Oumuamua

These celestial objects are known as "dark comets," which are astronomical objects that look like asteroids but strangely move through space like a comet. These odd objects were first discovered less than two years, but according to NASA the first inkling of dark comets was a March 2016 study that found an asteroid seemingly randomly deviated from its course, changing its orbit.

NASA writes the behavior of dark comets could explain the 2016 study documentation, as the lead author of the December 9 study, Davide Farnocchia of NASA's Jet Propulsion Laboratory in Southern California, explained, "When you see that kind of perturbation on a celestial object, it usually means it's a comet, with volatile material outgassing from its surface giving it a little thrust." However, when researchers looked through instruments, the object named 2003 RM appeared as an asteroid, just a single light dot on the display. By comparison, a comet typically has a long tail that is depicted as a thinning streak from a center point of light.

Then, Oumuamua was detected in 2017, the first interstellar visitor. It looked like an asteroid but moved as if it were outgassing like a comet, perking the interest of many astronomers.

"'Oumuamua was surprising in several ways," said Farnocchia. "The fact that the first object we discovered from interstellar space exhibited similar behaviors to 2003 RM made 2003 RM even more intriguing."

Fast-forward to 2023, and researchers have discovered enough of these objects that they got better at finding them, and have now found seven solar system objects that look like asteroids but move like comets, earning themselves the name "dark comets". The team discovered through analyzing the reflectivity of the dark comets and their orbits that there are two types of dark comets: outer dark comets and inner dark comets.

Outer dark comets have a highly eccentric or elliptical orbit, and are typically large with diameters of hundreds of meters or more. As for inner dark comets, these are located in the inner solar system near Mercury, Venus, Earth, and Mars. These dark comets travel in circular orbits and are typically smaller, measuring just tens of meters in diameter.

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