168P/Hergenrother
A periodic comet that fragmented after a 2012 outburst.
168P/Hergenrother is a periodic comet that orbits the Sun. It was first detected on November 22, 1998, when Carl W. Hergenrother identified it in CCD images taken the previous day by Timothy B. Spahr using the Catalina Sky Survey’s 0.41-meter telescope. Brian G. Marsden calculated its orbit, finding a period of 6.78 years. At discovery, the comet shone at magnitude 17 in Ursa Minor.
The comet was originally designated P/1998 W2. After its return in 2005, it received the temporary name P/2005 N2. Kazuo Kinoshita and Shuichi Nakano independently predicted its next perihelion around November 2, 2005, based on the 1998 apparition, and Australian astronomer David Herald successfully recovered it on November 6, 2005.
During its 2012 apparition, the comet reached perihelion on October 1. It was expected to brighten to about magnitude 15.2, but an outburst boosted it to magnitude 8—over 500 times brighter than normal. On October 19, the Virtual Telescope Project captured a dust cloud trailing the nucleus. By October 26, images from the 2-meter Faulkes Telescope North confirmed a fragmentation event, with a secondary fragment around magnitude 17. The 8.1-meter Gemini telescope later revealed at least four fragments from six separate breakups.
The comet’s next perihelion occurred on August 5, 2019, when it was 76 degrees from the Sun. It made its closest approach to Earth on November 6, 2019, at a distance of 1 AU (150 million km) with a solar elongation of about 110 degrees. It was not recovered until January 3, 2020, when it was 141 degrees from the Sun, but only two observations were reported from a single night. It was last observed in January 2020 and may have continued fragmenting after the 2012 outburst.
Spitzer Space Telescope observations from 2006–2007 originally estimated the nucleus at about 0.96 km in diameter before the 2012 fragmentation. A 2020 reanalysis revised this to 0.91 km.
Quick Facts
- Discovery Ref
- IAUC_7057
- Discoverer
- Carl W. Hergenrother
- Discovery Site
- Catalina Sky Survey
- Discovery Date
- 22 November 1998
- Mpc Name
- P/1998 W2, P/2005 N2
- Orbit Ref
- jpl1 · MPC
- Epoch
- 25 February 2023 (JD 2460000.5)
- Observation Arc
- 21.12 years
- Earliest Precovery Date
- 21 November 1998
- Obs
- 3,631
- Perihelion
- 1.357 AU
- Aphelion
- 5.817 AU
Facts from the source article.
Lore & Background
168P/Hergenrother was discovered on 22 November 1998 by Carl W. Hergenrother from CCD images taken by Timothy B. Spahr a day earlier with the Catalina Sky Survey's 0.41 m telescope. Preliminary orbital calculations by Brian G. Marsden revealed a periodic orbit of 6.78 years. At discovery, the comet was a 17th-magnitude object in Ursa Minor. Between 2000 and 2002, Kazuo Kinoshita and Shuichi Nakano independently used the comet's 1998 positions to predict its next perihelion around 2 November 2005, and it was recovered by David Herald on 6 November 2005.
The comet came to perihelion on 1 October 2012 and was expected to reach about magnitude 15.2, but an outburst caused it to reach magnitude 8, briefly more than 500 times brighter than without the outburst. On 19 October, images by the Virtual Telescope Project showed a dust cloud trailing the nucleus. Images by the Faulkes Telescope North on 26 October confirmed a fragmentation event, with a secondary fragment about magnitude 17. Further observations by the Gemini telescope showed the comet fragmented into at least four parts in six fragmentation events.
During its 2019 apparition, 168P came to perihelion on 5 August 2019, when it was 76 degrees from the Sun. It made a closest approach to Earth on 6 November 2019 at 1 AU with a solar elongation of about 110 degrees. It was not recovered until 3 January 2020, when only two observations on a single night were reported. The comet may have continued fragmenting after the 2012 outburst.
Reader's Guide
168P/Hergenrother's significance lies in its dramatic 2012 outburst, which provided a rare opportunity to study comet fragmentation in detail. The outburst, which made the comet over 500 times brighter than expected, was followed by multiple fragmentation events observed by large telescopes such as the Faulkes Telescope North and the Gemini telescope. These observations revealed that the nucleus, originally about 0.96 km in diameter (later revised to 0.91 km), broke into at least four parts across six fragmentation events. The comet's behavior highlights the dynamic and unpredictable nature of cometary nuclei. Its legacy includes the detailed record of its fragmentation, which contributes to understanding how comets evolve and disintegrate over time. The comet's last observation in January 2020, with only two reports on a single night, suggests it may have continued fragmenting, leaving its ultimate fate uncertain.
Did You Know?
- The comet was originally named P/1998 W2 and later given the temporary name P/2005 N2.
- During the 2012 outburst, the comet reached apparent magnitude 8, more than 500 times brighter than expected.
- The nucleus was originally about 0.96 km in diameter before fragmentation, later revised to 0.91 km.
More in Periodic Comets 1-24
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