168P/Hergenrother

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168P/Hergenrother
168p-hergenrother.jpg
168P/Hergenrother during its 2012 outburst as imaged from the Mount Lemmon Observatory
Discovery [1]
Discovered by Carl W. Hergenrother
Discovery site Catalina Sky Survey
Discovery date22 November 1998
Designations
P/1998 W2
P/2005 N2
Orbital characteristics [2] [3]
Epoch 25 February 2023 (JD 2460000.5)
Observation arc 21.12 years
Earliest precovery date21 November 1998
Number of
observations		3,631
Aphelion 5.817 AU
Perihelion 1.357 AU
Semi-major axis 3.587 AU
Eccentricity 0.62169
Orbital period 6.794 years
Inclination 21.615°
355.43°
Argument of
periapsis 		15.041°
Mean anomaly 188.01°
Last perihelion5 August 2019
Next perihelion18 May 2026
TJupiter 2.663
Earth MOID 0.420 AU
Jupiter MOID 0.001 AU
Physical characteristics [2] [4]
Mean diameter
0.91 km (0.57 mi)
Comet total
magnitude (M1)		7.0
Comet nuclear
magnitude (M2)		15.2
8.0
(2012 apparition)

168P/Hergenrother is a periodic comet in the Solar System. The comet originally named P/1998 W2 returned in 2005 and got the temporary name P/2005 N2. [5] The comet was last observed in January 2020 [3] and may have continued fragmenting after the 2012 outburst.

Contents

Observational history

Discovery

On 22 November 1998, Carl W. Hergenrother spotted a new comet from CCD images taken by Timothy B. Spahr a day earlier with the Catalina Sky Survey's 0.41 m (16 in) telescope. [6] Preliminary orbital calculations by Brian G. Marsden reveal that the comet has a periodic orbit of 6.78 years. [1] At the time, the comet was a 17th-magnitude object within the constellation Ursa Minor. [a]

Between 2000 and 2002, Kazuo Kinoshita and Shuichi Nakano independently used the comet's positions during its 1998 apparition to predict its next perihelion date, which is around 2 November 2005. [6] It was successfully recovered by Australian astronomer, David Herald, on 6 November 2005. [5]

2012 outburst

The comet came to perihelion on 1 October 2012, [7] and was expected to reach about apparent magnitude 15.2, but due to an outburst the comet reached apparent magnitude 8. [8] As a result of the outburst of gas and dust, the comet was briefly more than 500 times brighter than it would have been without the outburst. [b] On 19 October, images by the Virtual Telescope Project showed a dust cloud trailing the nucleus. [9] Images by the 2 m (79 in) Faulkes Telescope North on 26 October, [10] confirm a fragmentation event. [11] The secondary fragment was about magnitude 17. Further observations by the 8.1 m (320 in) Gemini telescope show that the comet fragmented into at least four parts in six fragmentation events. [10] [12] [13]

2019 apparition

168P came to perihelion on 5 August 2019, [3] when it was 76 degrees from the Sun. It then made a closest approach to Earth on 6 November 2019, when it was 1 AU (150 million km) from Earth with a solar elongation of about 110 degrees. It was not recovered until 3 January 2020, when it was 141 degrees from the Sun, but only two observations on a single night were reported.

Physical characteristics

Observations conducted by the Spitzer Space Telescope between 2006 and 2007 showed that Hergenrother's nucleus was originally about 0.96 km (0.60 mi) in diameter before it disintegrated on its 2012 outburst. [14] This was later revised to 0.91 km (0.57 mi) upon reanalysis of data in 2020. [4]

References

Notes

  1. ↑ Reported initial position upon discovery was: α = 21h 15m 03.67s, δ = –14° 37′ 45″ [1]
  2. ↑ Apparent magnitude:

Citations

  1. 1 2 3 C. W. Hergenrother (23 November 1998). B. G. Marsden (ed.). "Comet C/1998 W2 (Hergenrother)". IAU Circular. 7057.
  2. 1 2 "168P/Hergenrother – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory . Retrieved 1 April 2025.
  3. 1 2 3 "168P/Hergenrother Orbit". Minor Planet Center . Retrieved 20 June 2014.
  4. 1 2 M. L. Paradowski (2020). "A New Method of Determining Brightness and Size of Cometary Nuclei" (PDF). Monthly Notices of the Royal Astronomical Society. 492 (3): 4175–4188. Bibcode:2020MNRAS.492.4175P. doi: 10.1093/mnras/stz3597 .
  5. 1 2 D. Herald (5 July 2005). D. W. Green (ed.). "Comet P/2005 N2 (Hergenrother)". IAU Circular. 8560.
  6. 1 2 G. W. Kronk. "168P/Hergenrother". Cometography.com. Retrieved 1 April 2025.
  7. ↑ S. Nakano (23 April 2009). "168P/Hergenrother (NK 1778)". OAA Computing and Minor Planet Sections. Retrieved 20 February 2012.
  8. ↑ S. Yoshida (21 February 2012). "168P/Hergenrother (2012)". www.aerith.net. Retrieved 25 February 2012.
  9. ↑ G. Masi (19 October 2012). "Comet 168P/Hergenrother: hi-res images (19 Oct. 2012)". Virtual Telescope Project. Retrieved 18 October 2016.
  10. 1 2 D. C. Agle (2 November 2012). "Scientists Monitor Comet Break-up". jpl.nasa.gov. Jet Propulsion Laboratory. 2012-349. Retrieved 1 April 2025.
  11. ↑ G. Sostero; N. Howes; E. Guido (26 October 2012). "Splitting event in comet 168P/Hergenrother". Remanzacco Observatory in Italy – Comets & Neo. Retrieved 28 October 2012.
  12. ↑ P. Plait (5 November 2012). "Breaking up is easy to do. If you're a comet". Bad Astronomy. Archived from the original on 8 November 2012. Retrieved 6 November 2012.
  13. ↑ Z. Sekanina (2014). "Temporal Correlation Between Outbursts and Fragmentation Events of Comet 168P/Hergenrother". arXiv: 1409.7641 [astro-ph.EP].
  14. ↑ Y. R. Fernández; M. S. Kelley; P. L. Lamy; I. Toth; O. Groussin; et al. (2013). "Thermal Properties, Sizes, and Size Distribution of Jupiter-family Cometary Nuclei". Icarus. 226 (1): 1138–1170. arXiv: 1307.6191 . Bibcode:2013Icar..226.1138F. doi:10.1016/j.icarus.2013.07.021.
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