Hyperbolic asteroid

A hyperbolic asteroid is any sort of asteroid or non-cometary astronomical object observed to have an orbit not bound to the Sun and will have an orbital eccentricity greater than 1 when near perihelion.[1] Unlike hyperbolic comets, they have not been seen out-gassing light elements, and therefore have no cometary coma. Most of these objects will only be weakly hyperbolic and will not be of interstellar origin.

Orbit explanation

The planets and most satellites of the solar system revolve in an almost circular motion - called an elliptical orbit - around the Sun or their parent planet, so their orbital eccentricity is generally much closer to 0 than to 1. In mathematics, by definition, an eccentricity of 1 characterizes a parabola, and e > 1, a hyperbola. Some comets are on parabolic and hyperbolic orbits. This means that these hyperbolic asteroids all have an orbital eccentricity greater than 1.

Known hyperbolic asteroids

So far most hyperbolic asteroids discovered have later displayed cometary behavior by either outgassing or demonstrating motion based on solar radiation pressure. Hyperbolic Asteroids are orbital objects with an orbit not bound to the sun while near perihelion.[2] ʻOumuamua had the motion of a comet but was never seen outgassing and thus it is listed as a hyperbolic asteroid by the JPL Small-Body Database.[3]

Recent hyperbolic comets that were originally listed as hyperbolic asteroids include C/2017 U7 (A/2017 U7),[4] C/2018 C2 (Lemmon),[5] and C/2018 F4 (PANSTARRS).[6]

Two other asteroids currently have hyperbolic heliocentric orbits, A/2019 G4[7] and A/2019 O3.[8]

According to astronomer David Jewitt, it is likely that, as the solar system moves toward the Lyra constellation, more hyperbolic asteroids will come into the view of astronomers[9] as that is where ‘Oumuamua was observed coming from.

Perturbation

Asteroids can become ejected or in a highly eccentric orbit around the Sun by being ejected by planets like Jupiter. Just because an orbit solution looks unbound at an epoch when the object is near perihelion (closest approach to the Sun) does not mean the orbit will be unbound when beyond the planets.[10]

See also
  • ʻOumuamua, formerly designated a hyperbolic asteroid, but may be an exocomet instead.
  • Hyperbolic comet, a Solar System comet with an eccentricity greater than 1.
  • Interstellar object, an object arriving from outside the Solar System. Those objects usually have unbound (e>1) orbits.

References
  1. http://ssd.jpl.nasa.gov/sbdb_help.cgi?class=HYA
  2. "Hyperbolic Asteroids | Space Reference". www.spacereference.org. Retrieved 12 November 2019.
  3. "JPL Small-Body Database Search Engine: orbital class Hyperbolic Asteroid (HYA)". Jet Propulsion Laboratory Solar System Dynamics. Retrieved 4 March 2018.
  4. Web Archive from 5 March 2018 for A/2017 U7
  5. Web Archive from 5 March 2018 for A/2018 C2
  6. Web Archive from 28 March 2018 for A/2018 F4
  7. "(A/2019 G4)". JPL Small-Body Database Browser. Retrieved 28 December 2019.
  8. "A/2019 O3". JPL Small-Body Database Browser. Retrieved 28 December 2019.
  9. Croswell, Ken (2017). "Astronomers race to learn from first interstellar asteroid ever seen". Nature News. doi:10.1038/nature.2017.22925.
  10. de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl; Aarseth, Sverre J. (6 February 2018). "Where the Solar system meets the solar neighbourhood: patterns in the distribution of radiants of observed hyperbolic minor bodies". Monthly Notices of the Royal Astronomical Society Letters. 476 (1): L1–L5. arXiv:1802.00778. Bibcode:2018MNRAS.476L...1D. doi:10.1093/mnrasl/sly019.

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