C/2013 R1 (Lovejoy)

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

C/2013 R1 (Lovejoy) is a non-periodic comet discovered on 7 September 2013 using a 0.2 m (7.9 in) Schmidt–Cassegrain telescope.^[2] It is the fourth comet discovered by Terry Lovejoy. It crossed the celestial equator on 14 October 2013, which made it better observed from the Northern Hemisphere.

C/2013 R1 (Lovejoy)

C/2013 R1 (Lovejoy) from a 3-minute exposure taken using a 6" refractor on 28 November 2013
Discovery[1][2]
Discovered by	Terry Lovejoy
Discovery site	Thornlands, Australia
Discovery date	7 September 2013
Designations
Alternative designations	CK13R010[2]
Orbital characteristics[3][4]
Epoch	29 December 2013 (JD 2456655.5)
Observation arc	372 days (1.02 years)
Number of observations	3,894
Aphelion	~830 AU (outbound)
Perihelion	0.812 AU
Eccentricity	0.99843
Orbital period	~6,900 years (inbound) ~8,500 years (outbound)
Inclination	64.041°
Longitude of ascending node	70.711°
Argument of periapsis	67.166°
Mean anomaly	0.001°
Last perihelion	22 December 2013[5]
TJupiter	0.499
Earth MOID	0.146 AU
Jupiter MOID	1.564 AU
Physical characteristics[6]
Mean radius	1.266 ± 0.10 km (0.787 ± 0.062 mi)
Mean density	480±70 kg/m3
Synodic rotation period	47.8±1.2 hours[7]
Comet total magnitude (M1)	11.5[4]
Apparent magnitude	4.0 (2013 apparition)[8]

Observational history

By 1 November 2013, the comet was visible to the naked eye near the Beehive Cluster (M44), about halfway between Jupiter and Regulus.^[9] It became more impressive than C/2012 S1 (ISON).^[10] In binoculars, the comet has the appearance of a green, unresolved globular cluster.

C/2013 R1 made its closest approach to Earth on 19 November 2013 at a distance of 0.3967 AU (59.35 million km),^[4] and reached an apparent magnitude of about 4.5.^[11] On 27 November 2013 the comet was in the constellation of Canes Venatici, near the bottom of the handle of the Big Dipper. From 28 November until 4 December 2013, the comet was in the constellation Boötes. On 1 December 2013 it passed the star Beta Boötis.^[12] From 4 December until 12 December 2013, the comet was in the constellation Corona Borealis.

From 12 December until 14 January 2014, the comet was in the constellation Hercules. On 14 December 2013, it passed the star Zeta Herculis.^[12] The comet came to perihelion (closest approach to the Sun) on 22 December 2013 at a distance of 0.81 AU (121,000,000 km; 75,000,000 mi) from the Sun.^[5] At perihelion, the comet had an elongation of 51 degrees from the Sun. By September 2014, the comet had faded to magnitude 18.^[13]

Physical characteristics

Chemical composition

Narrow-band spectroscopy of the comet in December 2013 revealed that the coma of C/2013 R1 has a relatively high abundance in H₂O and CO₂ molecules.^[14] Additional photometry from TRAPPIST until July 2014 determined that the detected organic compounds on its coma (OH, NH, CN, C₃, and C₂) were partly caused by the breakdown of HCN outgassing from the comet.^[15]

Infrared observations from the Keck Observatory detected enriched amounts of CO, as well as hydrocarbons like CH₄, C₂H₆, and CH₃OH, indicating the variability of chemicals found in other Oort cloud comets.^[16] Other complex organic compounds, such as HCOOH, CH₃CHO, (CH₂OH)₂ and NH₂CHO, were also detected from the comet.^[17]

Nucleus size and rotation

The nucleus of C/2013 R1 is estimated to be about 1.266±0.10 km in radius, with a low bulk density of roughly about 480±70 kg/m³.^[6] Measurements of the dust emission structures around the comet determined that it has a rotation period about 47.8±1.2 hours in length.^[7]