A hyperbolic asteroid is any sort of
asteroid
An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...
or non-
comet
A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...
ary astronomical object observed to have an orbit not bound to the
Sun and will have an
orbital eccentricity
In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values be ...
greater than 1 when near
perihelion. Unlike
hyperbolic comets, they have not been seen out-gassing
light elements, and therefore have no cometary
coma
A coma is a deep state of prolonged unconsciousness in which a person cannot be awakened, fails to Nociception, respond normally to Pain, painful stimuli, light, or sound, lacks a normal Circadian rhythm, sleep-wake cycle and does not initiate ...
. 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
The Solar SystemCapitalization 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 "Sola ...
revolve in an almost circular motion – called an
elliptical orbit
In astrodynamics or celestial mechanics, an elliptical orbit or eccentric orbit is an orbit with an orbital eccentricity, eccentricity of less than 1; this includes the special case of a circular orbit, with eccentricity equal to 0. Some or ...
– 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 (''e'') 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.
ʻOumuamua
Oumuamua is the first confirmed interstellar object detected passing through the Solar System. Naming of comets#Current system, Formally designated 1I/2017 U1, it was discovered by Robert Weryk using the Pan-STARRS telescope at Haleakalā O ...
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.
* Recent hyperbolic comets that were originally listed as hyperbolic asteroids include
C/2017 U7 (A/2017 U7),
C/2018 C2 (Lemmon),
C/2018 F4 (PANSTARRS),
C/2019 O3 (Palomar),
and C/2019 G4.
* 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
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
Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
. Just because an orbit solution looks unbound at 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 b ...
when the object is near
perihelion (closest approach to the Sun) does not mean the orbit will be unbound when beyond the planets.
[
]
See also
* ʻOumuamua
Oumuamua is the first confirmed interstellar object detected passing through the Solar System. Naming of comets#Current system, Formally designated 1I/2017 U1, it was discovered by Robert Weryk using the Pan-STARRS telescope at Haleakalā O ...
, formerly designated a hyperbolic asteroid, but may be an exocomet instead.
* Hyperbolic comet, a Solar System comet with an eccentricity greater than 1.
*
References
External links
MPEC 2019-U194 : A/2019 G4 and A/2019 S4
'' Minor Planet Electronic Circular'', 27 October 2019
A/2019 O3
Minor Planet Center
A/2019 G4
Minor Planet Center
A/2017 U7
Minor Planet Center
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Hypothetical astronomical objects