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Astronomers have spotted what they believe to be the second interstellar object ever observed in the solar system.
Comet C / 2019 Q4. Image credit: G. Borisov.
C / 2019 Q4 is a relatively large active comet with a diameter between 1.2 and 10 miles (2-16 km).
Also designated 2I / Borisov, the object was discovered by Gennady Borisov, an amateur astronomer from Crimea, Ukraine on August 30, 2019.
About a week later, astronomers from NASA and ESA got images of the object and made several position measurements. The data confirmed the unusual orbit of the object, which was first reported by the NASA Scout system.
"We can learn a lot about the shape of its orbit, especially its eccentricity – how far it is stretched," said Dr. Marco Micheli of ESA's Center for Near-Earth Objects Coordination and colleagues.
"The planets in almost perfect circular orbit around their star, the Earth for example, have an eccentricity close to zero."
"Comets and asteroids orbiting a body whose trajectories are elongated are described as having an eccentricity between zero and one, and objects with an eccentricity greater than one," hyperbolic "orbits, are interstellar.
Current observations suggest that C / 2019 Q4 is interstellar, its orbit being greatly elongated with an eccentricity of 3.14.
"The current speed of the comet is high, about 150 000 km / h (150 000 km / h), which is much higher than the typical speed of objects orbiting the Sun at this distance," said Dr. Davide. Farnocchia from NASA's Center for Near-Earth Objects Studies.
"The high speed not only indicates that the object is probably coming from outside our solar system, but also that it will leave and return to interstellar space."
The hyperbolic orbit of C / 2019 Q4. Image credit: ESA.
C / 2019 T4 is moving towards the inner solar system and is currently 260 million km (420 million km) from the Sun.
On October 26, 2019, the comet will pass through the ecliptic plane – the plane in which the Earth and other planets gravitate around the Sun – from above, at an angle of about 40 degrees.
On December 9, he is expected to be closest to the Sun, less than 293 million kilometers from our star.
It will reach its closest point to Earth on December 28th at a distance of about 283 million km (176 million miles).
"We are now working to obtain more observations of this unusual object," Dr. Micheli said.
"We have to wait a few days to understand its origin with observations that will either prove the current thesis that it is interstellar or may radically change our understanding."
The discovery of T4 C / 2019 was announced in the Circular electronic minor planet Bulletin (MPEC) published by the Minor Planet Center of the International Astronomical Union on September 13, 2019.
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H. Mikuz et al. Comet C / 2019 Q4 (Borisov). Circular electronic minor planet # 2019-R113
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