Paris (AFP)
And two! A comet from elsewhere has been spotted in our solar system, according to a study published Monday in Nature Astronomy. This is the second of its kind after the discovery in 2017 of Oumuamua, a strange cigar-shaped object.
It all began on August 30, when Gennady Borisov, an amateur astronomer, spotted a racing car in the sky. Alerted, astronomers are bending over the unknown object.
They are then formal: the analysis of the collected data shows that its orbit can not have its origin inside our solar system. It comes from another star system. But which one? It remains a mystery.
"We quickly organized sightings with the William Herschel Telescope (WHT) and the Gemini Observatory," told AFP Piotr Guzik, from the Jagiellonian University in Krakow, Poland. Co-author of the study, he remembers a mixture of excitement and amazement.
While Oumuamua was alternatively called an asteroid, an alien spacecraft and a comet, the nature of the little one leaves little doubt: astronomers could see his coma ("hair") and his tail, characteristics of known comets.
Concerning the new comet named 2I / Borisov, in homage to its discoverer, the team was able to determine that it is mainly composed of dust, that it has a slightly reddish color and that its solid nucleus is about 1 km radius.
It should also be observed in December when it will be even closer to the Sun.
Oumuamua had been spotted by the Pan-STARRS1 telescope in Hawaii, hence its name, which means "messenger" in Hawaiian. It is approximately 400 meters long and 40 meters wide, and has been tracked by several telescopes as the first detected object from another star system.
Comets are composed of ice, organic materials and rocks from ancient stars and interstellar clouds.
When they get closer to the Sun, the ice turns into gas. The mixture of gas and dust forms the tail of the comet.
© 2019 AFP