C/2018 C2 (Lemmon)

For other comets of the same name, see Comet Lemmon.

C/2018 C2 (Lemmon)

The orbit of C/2018 C2 (Lemmon)
Discovery [1]
Discovery site	Mount Lemmon Observatory
Discovery date	5 February 2018
Designations
MPC designation	C/2018 C2, A/2018 C2
Alternative designations	ZC82561
Orbital characteristics [2] [3]
Epoch	20 May 2018 (JD 2458258.5)
Observation arc	272 days
Earliest precovery date	28 January 2018
Number of observations	1,672
Aphelion	~50,000 AU (inbound) ~5,170 AU (outbound)
Perihelion	1.956 AU
Semi-major axis	~25,700 AU (inbound) ~2,590 AU (outbound)
Eccentricity	0.99992 (inbound) 0.99925 (outbound)
Orbital period	~4.1 million years (inbound) ~130,000 years (outbound)
Inclination	34.453°
Longitude of ascending node	91.139°
Argument of periapsis	134.14°
Last perihelion	2 June 2018
Earth MOID	1.062 AU
Jupiter MOID	1.405 AU
Physical characteristics [4]
Mean radius	4.4±0.5 km
Geometric albedo	0.04 (assumed)
Spectral type	(B–V) = 0.75±0.03 (V–R) = 0.41±0.02 (R–I) = 0.37±0.03
Comet total magnitude (M1)	7.6 [3]
Comet nuclear magnitude (M2)	14.8 [3]
Apparent magnitude	15.2 (2018 apparition) [5]

C/2018 C2 (Lemmon) is a hyperbolic comet (previously classified as A/2018 C2, a hyperbolic asteroid). It was first observed on 5 February 2018 by the Mount Lemmon Survey conducted at the Mount Lemmon Observatory near Tucson, Arizona. ^[6] The discovery was announced on 4 March 2018 along with another hyperbolic object, A/2017 U7. ^[1] On 22 March 2018 it was determined to be a hyperbolic comet. ^[7]

Orbit

Heliocentric eccentricity from 2000–2035 which is strongly influenced by Jupiter's 12 year orbital period.

The path of C/2018 C2 across the sky with annual retrograde loops

While near perihelion, A/2018 C2's heliocentric orbit is not bound to the Solar System, unlike ʻOumuamua, it is not an interstellar object. The heliocentric eccentricity drops below 1 starting with an epoch of January 2023, ^[8] when it is 13.8 AU from the Sun, making the orbit bound to the Sun before it leaves the planetary region of the Solar System. The more stable barycentric orbit of A/2018 C2, shows that it is only a very distant small Solar System body, approaching as far as 50,000  AU from the Sun, around the distance of the Oort Cloud. It had an orbital period of millions of years until the current approach to the Solar System, where perturbations will shorten the orbit drastically to about 5,200 AU, with an orbital period of 130,000 years. ^[2] Hui Man-To calculated that the comet would have its next perihelion after 130 to 140 thousands years, at a distance of about 2 AU. ^{[4] [2]}

As of March 2018 ^[update] , A/2018 C2 was inbound 2.2 AU (330,000,000 km; 200,000,000 mi) from the Sun. ^[1] A/2018 C2 made its closest approach to the Sun on 2 June 2018 at a distance of 1.9 AU (280 million km) (outside the orbit of Mars). ^[3] Since this object out gassed generating a cometary coma while near the inner Solar System, it was reclassified as a hyperbolic comet. ^[4]

References

1. "MPEC 2018-E18 : A/2018 C2". IAU Minor Planet Center. 4 March 2018. Retrieved 4 March 2018. (AK18C020)
2. Horizons output. "Barycentric Osculating Orbital Elements for Comet C/2018 C2 (Lemmon)" . Retrieved 15 October 2022.
3. "JPL Small-Body Database Browser: (A/2018 C2)" (2018-02-27 last obs.). Jet Propulsion Laboratory. Archived from the original on 5 March 2018. Retrieved 5 March 2018.
4. M. T. Hui (2018). "Two Hyperbolic Baldheads in the Solar System: 2017 U7 and 2018 C2". The Astronomical Journal. 156 (2): 73. arXiv: 1806.06904 . Bibcode:2018AJ....156...73H. doi: 10.3847/1538-3881/aacdf3 . S2CID   250760308.
5. "Observation list for C/2018 C2". COBS – Comet OBServation database. Retrieved 2 December 2025.
6. "C/2018 C2". Minor Planet Center. Retrieved 5 March 2018.
7. "MPEC 2018-F136: COMET C/2018 C2 (Lemmon)". IAU Minor Planet Center. 28 March 2018. Retrieved 28 March 2018. (CK18C020)
8. Horizons output. "Heliocentric orbit of Comet C/2018 C2 (Lemmon) becoming CLOSED in January 2023" . Retrieved 16 October 2022.

External links

• C/2018 C2 at the JPL Small-Body Database
  • Close approach  · Discovery  · Ephemeris  · Orbit viewer  · Orbit parameters  · Physical parameters