96P/Machholz
 96P/Machholz as seen by STEREO-A in April 2007 | |
| Discovery | |
|---|---|
| Discovered by | Donald Machholz[1] |
| Discovery date | May 12, 1986 |
| Alternative designations | 96P, Machholz, Machholz 1, 1986 J2, 1991 XII, 1986e, 1986 VII |
| Orbital characteristics A | |
| Epoch |
2007-Apr-15 (JD 2454205.5)[1] |
| Aphelion | 5.9079 AU |
| Perihelion | 0.12461 AU |
| Semi-major axis | 3.0162 AU |
| Eccentricity | 0.95868 |
| Orbital period | 5.24 yr |
| Inclination | 59.955° |
| Last perihelion |
July 14, 2012 18:49[2][3][4] April 4, 2007[2] January 8, 2002[2] |
| Next perihelion | October 27, 2017[4] |
Comet 96P/Machholz or 96P/Machholz 1[5] is a short-period comet discovered on May 12, 1986 by amateur astronomer Donald Machholz on Loma Prieta peak, in central California using 130 millimetres (5.1 in) binoculars.[5][6] On June 6, 1986, comet 96P/Machholz passed 0.40373 AU (60,397,000 km; 37,529,000 mi) from the Earth.[7] Comet 96P/Machholz last came to perihelion on July 14, 2012,[2] and will next come to perihelion on October 27, 2017.[4] 96P/Machholz has an estimated radius of around 3.2 km.[8]
Machholz 1 is unusual among comets in several respects. Its highly eccentric 5.2 year orbit has the smallest perihelion distance known among numbered/regular[9] short-period comets, bringing it considerably closer to the Sun than the orbit of Mercury. It is also the only known short-period comet with both high orbital inclination and high eccentricity.[8] In 2007, Machholz 1 was found to be both carbon-depleted and cyanogen-depleted, a chemical composition nearly unique among comets with known compositions.[10][11] The chemical composition implies a different and possible extrasolar origin.[12]
Orbit
The orbit of Machholz 1 corresponds to the Arietids and the Marsden and Kracht Comet groups.[13] Its Tisserand parameter with respect to Jupiter, TJ, is 1.94 and comets are generally classified as Jupiter family if TJ > 2.[8] Orbital integrations indicate that TJ was greater than 2 about 2500 years ago.[8] Machholz 1 is currently in a 9:4 orbital resonance with Jupiter.[8] 96P will not make another close approach to the Earth until 2028, when it will pass at a distance of 0.319 AU (47,700,000 km; 29,700,000 mi).[7]
Observations
Machholz 1 entered the field of view of the orbiting Solar and Heliospheric Observatory (SOHO) in 1996, 2002, and 2007, where it was seen by the corona-observing LASCO instrument in its C2 and C3 coronagraphs.[5][14] During the 2002 passage the comet brightened to magnitude −2,[15] and was very impressive as seen by SOHO.[16] During the comet's last perihelion passage in 2007, it appeared in SOHO's LASCO C3's field of view from April 2 to April 6, peaking in brightness on April 4, 2007,[17] around magnitude +2.[18] In these observations, its coma was substantially smaller than the Sun in volume, but the forward scattering of light made the comet appear significantly brighter.[19]
The most recent opportunity to observe Machholz 1 was when it returned to perihelion in 2012.[12] Between July 12–17, 2012, comet Machholz was visible in the SOHO LASCO/C3 field of view and expected to brighten to about magnitude +2.[20] Two small faint fragments of Comet Machholz were detected in the SOHO C2 images.[21] The fragments were 5 hours ahead of Comet Machholz, and probably fragmented from the comet during the 2007 perihelion passage.[21]
Unusual composition
Spectrographic analysis of the coma of Machholz 1 was made during its 2007 apparition, as part of the Lowell Observatory comet composition long-term observing program.[22] When compared with the measured abundances of five molecular species in the comae of the other 150 comets in their database, these measurements showed Machholz 1 to have far fewer carbon molecules than the 150 other comets.[8] These other comets had on average 72 times as much cyanogen as Machholz 1.
The only comet previously seen with similar depletion both in carbon-chain molecules and cyanogens is Yanaka (1988r; 1988 Y1), but it has a substantially different orbit.[23]
Possible cause of the unusual chemical composition
There are currently three hypotheses to explain the chemical composition of Machholz 1.
Extrasolar origin
One hypothesis for the difference is that Machholz 1 was an interstellar comet from outside the Solar System and was captured by the Sun.[24]
Oort cloud origin
Other possibilities are that it formed in an extremely cold region of the Solar System (such that most carbon gets trapped in other molecules).
Extreme thermal alteration
Given how close it approaches the Sun at perihelion, repeated baking by the Sun has stripped most of its cyanogen.
References
- ↑ 1.0 1.1 "JPL Small-Body Database Browser: 96P/Machholz 1". Jet Propulsion Laboratory. 2007-08-12 last obs. Retrieved 2012-02-01.
- ↑ 2.0 2.1 2.2 2.3 Seiichi Yoshida (2007-12-30). "96P/Machholz 1". aerith.net. Archived from the original on 27 April 2011. Retrieved 2011-04-06.
- ↑ Syuichi Nakano (2009-04-22). "96P/Machholz 1 (NK 1771)". OAA Computing and Minor Planet Sections. Retrieved 2012-02-20.
- ↑ 4.0 4.1 4.2 Horizons output. "Observer Table for 96P/Machholz 1". Retrieved 2012-07-16. (Observer Location:@sun)
- ↑ 5.0 5.1 5.2 Gary W. Kronk. "96P/Machholz 1". Cometography. Archived from the original on 5 July 2008. Retrieved 2008-08-06.
- ↑ "Astronomy magazine podcast: Don Machholz and Comet 96P". Astronomy.com. March 29, 2007. Retrieved 2008-08-06.
- ↑ 7.0 7.1 "JPL Close-Approach Data: 96P/Machholz 1". 2007-08-12 last obs. Retrieved 2011-09-13.
- ↑ 8.0 8.1 8.2 8.3 8.4 8.5 Schleicher, David G. (2008). "The Extremely Anomalous Molecular Abundances of Comet 96P/MACHHOLZ 1 from Narrowband Photometry". The Astronomical Journal 136 (5): 2204–2213. Bibcode:2008AJ....136.2204S. doi:10.1088/0004-6256/136/5/2204.
- ↑ A'Hearn, M. F.; Millis, R. L.; Schleicher, D. G.; Osip, D. J.; Birch, P. V. (1995). "The ensemble properties of comets: Results from narrowband photometry of 85 comets, 1976-1992.". Icarus 118 (2): 223–270. Bibcode:1995Icar..118..223A. doi:10.1006/icar.1995.1190. (login required)
- ↑ "IAU Circular 8842". International Astronomical Union. 2007-06-06. Retrieved 2011-07-05.
- ↑ Langland-Shula, Laura E.; Graeme H. Smith (2007). "The Unusual Spectrum of Comet 96P/Machholz". The Astrophysical Journal Letters (IOP publishing) 664 (2): L119–L122. arXiv:0706.2022. Bibcode:2007ApJ...664L.119L. doi:10.1086/520839.
- ↑ 12.0 12.1 MacRobert, Alan (2008-12-02). "A Very Oddball Comet". Sky & Telescope magazine. Archived from the original on 7 December 2008. Retrieved 2008-12-05.
- ↑ Ohtsuka, Katsuhito; Nakano, Syuichi; Yohikawa, Makoto (February 2003). "On the Association among Periodic Comet 96P/Machholz, Arietids, the Marsden Comet Group, and the Kracht Comet Group.". Science Links Japan. Retrieved 2008-08-06.
- ↑ Boschat, Mike (January 7, 2002). "(meteorbs) Comet 96P/Machholz now in the SOHO C3 images". meteorbs. Archived from the original on 6 July 2008. Retrieved 2008-08-06.
- ↑ Seiichi Yoshida (May 29, 2007). "96P/Machholz 1 (2002)". arieth.net. Retrieved 2012-02-03.
- ↑ "Exclusive Views of Comet 96P/Machholz". SOHO hotshots. January 6–10, 2002. Retrieved 2012-02-03.
- ↑ SOHO Movie Theater
- ↑ Seiichi Yoshida (September 20, 2007). "96P/Machholz 1 (2007)". arieth.net. Archived from the original on 29 August 2008. Retrieved 2008-08-06.
- ↑ Marcus, Joseph C. (2007). "Forward-Scattering Enhancement of Comet Brightness. I. Background and Model". International Comet Quarterly 29 (2): 39–66. Bibcode:2007ICQ....29...39M.
- ↑ Michal Kusiak. "Transits of Objects through the LASCO/C3 field of view (FOV) in 2012". Sungrazing Comets @ Navy.mil. Retrieved 2012-02-01.
- ↑ 21.0 21.1 Battams, Karl (July 16, 2012). "Breaking News: Comet Machholz had babies!!". Sungrazing Comets. Navy.mil. Retrieved 2012-07-16.
- ↑ "A New Compositional Class of Comets: from Fire, Ice, or Beyond? Lowell Observatory Astronomer Confirms New Class of Comets". Lowell Observatory press release. 2008-12-02. Retrieved 2008-12-05.
- ↑ Fink, Uwe (1992). "Comet Yanaka (1988r): A New Class of Carbon-Poor Comet". Science 257 (5078): 1926. Bibcode:1992Sci...257.1926F. doi:10.1126/science.257.5078.1926. PMID 17753496.
- ↑ Jeanna Bryner (2 December 2008). "Odd Comet Possibly from Another Star System". Space.com.
External links
- 96P/Machholz 1 at the JPL Small-Body Database
- SOHO hotshots of comet
- video of 96P/ Machholz in STEREO HI1a
- For the fourth time since launch in 1995, SOHO/LASCO sees Comet 96/P Machholz! (13 July 2012)
- Family ties: Meet the Machholz's -- possibly the most complex family in the solar system!
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