The second-ever interstellar comet sighting has recently been made, only two years after 'Oumuamua was discovered.
Astronomers believe they have detected another space rock that was formed in a distant system before traveling across space to reach our solar system.
The object, a comet named C/2019 Q4 (Borisov), was recently sighted by the Minor Planet Center.
Detecting an interstellar object
How do astronomers know an object has come from outside of our solar system? As the Smithsonian reports, it's down to speed and trajectory. According to observations made of the comet, C/2019 Q4 is moving too fast — it's going at approximately 30.7 kilometers per second (68,700 miles per hour) — to have originated in our own solar system.
The comet was first observed by Gennady Borisov, a Ukrainian amateur astronomer at the Crimean Astrophysical Observatory, on 30 August.
An interstellar traveler
As the National Geographic reports, the space rock will come to within 180 million miles of Earth on 29 December and will make its closest approach to the Sun on 7 December. After passing the Sun, it will slingshot back out of our solar into interstellar space.
Observations by astronomers have allowed them to determine that C/2019 Q4 is two miles wide, with a coma of gas and dust that surrounds the object as it moves through space.
“Based on the available observations, the orbit solution for this object has converged to the hyperbolic elements shown below, which would indicate an interstellar origin,” a statement from the Minor Planet Center says.
“Further observations are clearly very desirable.”
As it makes its closest approach to Earth, astronomers will point their telescopes to the sky to confirm whether this is, in fact, another interstellar comet.
A study on the initial observations of the comet was published today in Nature Astronomy.