The following is a list of
Halley-type comets (HTCs), which are
periodic comet
Periodic comets (also known as short-period comets) are comets with orbital periods of less than 200 years or that have been observed during more than a single perihelion passage (e.g. 153P/Ikeya–Zhang). "Periodic comet" is also sometimes us ...
s with an orbital period between 20 and 200 years, often appearing only once or twice within one's lifetime. The majority come from between the orbits of Saturn and Neptune. Due to the nature of their orbits, they can be perturbed by the giant planets and sent into orbits too far from the Sun to outgas, and vice versa.
Minor planet
According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet. Before 2006, the IAU officially used the term ''minor ...
s in comet-like orbits similar to HTCs that never come close enough to the Sun to outgas are called
centaurs
A centaur ( ; grc, κένταυρος, kéntauros; ), or occasionally hippocentaur, is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse.
Centaurs are thought of in many Greek myths as bein ...
. HTCs are named after the first discovered member, and the first discovered periodic comet,
Halley's Comet
Halley's Comet or Comet Halley, officially designated 1P/Halley, is a short-period comet visible from Earth every 75–79 years. Halley is the only known short-period comet that is regularly visible to the naked eye from Earth, and thus the on ...
, which orbits the Sun in about 75 years, and passing as far as the orbit of
Neptune
Neptune is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 time ...
.
Most of the comets that have a period between 20 and 200 years (making them HTCs based on the classical definition) are actually officially classified as either Jupiter-family comets (JFCs) or Chiron-type comets (CTCs), based on their
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-thousand ...
Tisserand's parameter
Tisserand's parameter (or Tisserand's invariant) is a value calculated from several orbital elements ( semi-major axis, orbital eccentricity and inclination) of a relatively small object and a larger " perturbing body". It is used to distinguish d ...
(T
Jupiter). Although JFCs are classically defined by (
P < 20 y), they're officially defined by (2 < T
Jupiter < 3). CTCs, on the other hand, are officially defined by (T
Jupiter > 3;
a > a
Jupiter). Since they do not include any period-related constraints, some of the 20–200 year-period comets unfortunately match one of the classifications, making comet classifications even more vague.
Numbered HTCs
For the 14 numbered HTCs, see the
list of numbered comets, where they are labelled "HTC" in column "class".
Unnumbered HTCs
This list contains only Halley-type comets which are not numbered yet because they have been observed only once. Comets that belong to a different comet classification based on its Jupiter Tisserand parameter are given its alternative classification next to the comets' name.
See also
*
List of comets by type
*
List of near-parabolic comets
The following is a list of comets with a very high eccentricity (generally 0.99 or higher) and a period of over 1,000 years that do not quite have a high enough velocity to escape the Solar System. Often, these comets, due to their extreme semimaj ...
*
List of hyperbolic comets
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 ...
References
{{Portal bar, Astronomy, Stars, Spaceflight, Outer space, Solar System
Halley-type comets