C/2017 U7 (PanSTARRS) is a

hyperbolic comet This is a list of parabolic and hyperbolic comets in the Solar System. Many of these comets may come from the Oort cloud, or perhaps even have interstellar origin. The Oort Cloud is not gravitationally attracted enough to the Sun to form into ...

(previously classified as A/2017 U7, a hyperbolic asteroid), first observed on 29 October 2017 by astronomers of the

Pan-STARRS The Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1; obs. code: F51 and Pan-STARRS2 obs. code: F52) located at Haleakala Observatory, Hawaii, US, consists of astronomical cameras, telescopes and a computing facility that is ...

facility at Haleakala Observatory, Hawaii, United States when the object was from the Sun. Despite being discovered only 10 days after interstellar asteroid 1I/'Oumuamua, it was not announced until March 2018 (along with C/2018 C2 (Lemmon), which was believed to be another hyperbolic asteroid at the time) as its orbit is not strongly hyperbolic beyond most

Oort Cloud The Oort cloud (), sometimes called the Öpik–Oort cloud, first described in 1950 by the Dutch astronomer Jan Oort, is a theoretical concept of a cloud of predominantly icy planetesimals proposed to surround the Sun at distances ranging from ...

comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail. These phenomena ...

s. Based on the

absolute magnitude Absolute magnitude () is a measure of the luminosity of a celestial object on an inverse logarithmic astronomical magnitude scale. An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if it ...

of 10.6, it may measure tens of kilometers in diameter. As of August 2018, there is only 1 hyperbolic asteroid known,

ʻOumuamua Oumuamua is the first known interstellar object detected passing through the Solar System. Formally designated 1I/2017 U1, it was discovered by Robert Weryk using the Pan-STARRS telescope at Haleakalā Observatory, Hawaii, on 19 October ...

, but hundreds of

s are known.

Orbit

Although C/2017 U7's orbit is no longer bound to the

Solar System The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...

, unlike

, it is probably not an

interstellar object An interstellar object is an astronomical object (such as an asteroid, a comet, or a rogue planet, but not a star) in interstellar space that is not gravitationally bound to a star. This term can also be applied to an object that is on an inter ...

. It had an inbound orbital period of roughly 800000 years. Its point of origin is inclined only 3.5 degrees from the galactic plane, but its

aphelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ell ...

points roughly to the

Galactic anticenter The galactic anticenter is a direction in space directly opposite to the Galactic Center, as viewed from Earth. This direction corresponds to a point on the celestial sphere. From the perspective of an observer on Earth, the galactic anticenter ...

, so if it did somehow originate from interstellar space with a typical Solar System velocity (which is highly unlikely) it would have been traveling on an unusual orbit directly into the galactic core from beyond the Sun's orbit around the Milky Way. A barycentric orbit of C/2017 U7, however, shows that it is only a very distant Solar System object, approaching as far as 16,000 ± 1,000 AU from the Sun, around the distance of the

. It had an inbound orbital period of roughly 740,000 years until the current approach to the Solar System, where perturbations show it on an extremely weak

hyperbolic trajectory In astrodynamics or celestial mechanics, a hyperbolic trajectory or hyperbolic orbit is the trajectory of any object around a central body with more than enough speed to escape the central object's gravitational pull. The name derives from the f ...

after leaving the planetary region of the Solar System. The barycentric eccentricity increases above 1 starting with an

epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided by ...

of July 2022, reaching 1.0000088 once it gets beyond planetary perturbations. , C/2017 U7 is inbound from the Sun. C/2017 U7 makes closest approach to the Sun on 10 September 2019 at a distance of 6.4 AU (outside of

Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousandth t ...

's orbit). Due to the

orbital inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Earth ...

, on 18 May 2020, the asteroid will be about from Jupiter, generating a peak heliocentric eccentricity at 1.003. The dynamical analysis shows that the object has probably originated in the Oort cloud, however an interstellar origin cannot be discarded. 2017U7-skypath.png, Path across sky 2017U7-orbit.png, Hyperbolic trajectory through solar system

Physical characterization

The spectra and the colors of the hyperbolic comet C/2017 U7 (PANSTARRS) are atypical and the feature and overall spectral shape can be reproduced by laboratory spectra of kerite, a template for aliphatic-rich hydrocarbons that has been previously identified in NIR cometary spectra absorptions.

Notes

References

External links

* {{DEFAULTSORT:C/2017 U7 Hyperbolic comets Discoveries by Pan-STARRS 20171029