97P/Metcalf–Brewington

97P/Metcalf–Brewington is a periodic Jupiter-family comet originally discovered by Joel H. Metcalf in 1906 but subsequently lost.^[6] A new observation in 1991 by Howard J. Brewington was matched to the 1906 sighting; the orbit was computed and the comet was observed again on its returns to perihelion in 2001, 2011, and 2022.^[6]

97P/Metcalf–Brewington

Comet Metcalf–Brewington imaged by the Zwicky Transient Facility on 10 November 2021
Discovery[1][2]
Discovered by	Joel H. Metcalf Howard J. Brewington
Discovery site	Taunton, Massachusetts Cloudcroft, New Mexico
Discovery date	10 October 1906 7 January 1991
Designations
MPC designation	P/1906 V2, P/1991 A1
Alternative designations	1906 VI, 1991 I 1906h, 1991a
Orbital characteristics[3][4]
Epoch	31 March 2024 (JD 2460400.5)
Observation arc	115.20 years
Number of observations	607
Aphelion	6.960 AU
Perihelion	2.572 AU
Semi-major axis	4.766 AU
Eccentricity	0.4593
Orbital period	10.406 years
Inclination	17.949°
Longitude of ascending node	184.08°
Argument of periapsis	230.10°
Mean anomaly	73.309°
Last perihelion	15 February 2022
Next perihelion	19 July 2032[5]
TJupiter	2.710
Earth MOID	1.656 AU
Jupiter MOID	0.109 AU
Physical characteristics[3]
Dimensions	3.4 km (2.1 mi)
Comet total magnitude (M1)	13.7

Observational history

1906 discovery

On photographic plates taken on 15 November 1906, Joel H. Metcalf discovered the comet as a 12th-magnitude object within the constellation Eridanus.^[a]

1914–1922 apparitions and loss

The comet passed about 0.86 AU (129 million km) from Jupiter on September 1911, perturbing its orbit enough for astronomers to revise their calculations for the 1914 and 1922 apparitions.^[7] Henrietta Swan Leavitt reported that she may have recovered Metcalf's comet in 1915, however the two images she took were later confirmed to be that of 393 Lampetia instead.^[8] The comet was never found after its last reported observation on 16 January 1907 and after a series of orbital calculations showed that viewing conditions were unfavorable on each subsequent apparition until 1975,^[2] it was declared lost after 1922.^[7]

1991 rediscovery

Until 1975, Metcalf's comet was expected to appear no brighter than magnitude 18, although no attempts were made to find the comet due to unfavorable conditions.^[9] In 7 January 1991, Howard J. Brewington discovered a new comet within the constellation Cetus,^[b] which was verified by Alan Hale in the same night.^[10] Following additional observations by Katsuhito Ohtsuka and Robert H. McNaught between 7 and 9 January 1991, Brian G. Marsden noted that the orbit of Brewington's comet strongly resembled that of Metcalf's comet in 1906, concluding that they are one and the same object.^[11] It is later determined that the previous calculations for the 1914 and 1922 apparitions were off by a few days and a couple months respectively, which caused the failure of this comet's recovery during those apparitions.^[7]

Analysis of its light-curve revealed that during its 1991 apparition, comet Metcalf–Brewington had just experienced a massive outburst that brightened up the comet by 11 magnitudes!^[12] It was later determined that it might be caused by thermal stresses on an exposed ice pocket rich in hydrogen cyanide (HCN) gas, which cracked the crust of its nucleus during perihelion.^[12]

Recent observations

Shortly after being recovered, revised orbital calculations for the comet has revealed that it made a close encounter with Jupiter at a distance of 0.11 AU (16 million km) in March 1993, where it was also predicted to return by 2000 or 2001.^[13]

In October 2021, the comet experienced an outburst that expelled material out to 19,400 km (12,100 mi) from its nucleus, resulting in a temporary rise in apparent magnitude from 18 to 16.^[14]

See also

• C/1991 Y1 (Zanotta–Brewington)