C / 2017 K2 (PANSTARRS)

C / 2017 K2 (PANSTARRS) ^[i]

Hubble image from June 27, 2017
Properties of the orbit ( animation ) Epoch: March 2nd, 2019 ( JD 2,458,544.5)
Orbit type	hyperbolic (see chapter orbit)
Numerical eccentricity	1,00037
Perihelion	1,804 AU
Inclination of the orbit plane	87.5 °
Perihelion	December 20, 2022
Orbital velocity in the perihelion	31.4 km / s
Physical properties of the core
Medium diameter	<18 km (estimated)
Albedo	0.04 (assumption)
history
Explorer	Richard J. Wainscoat et al.
Date of discovery	May 21, 2017
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . Please also note the note on comet articles .

C / 2017 K2 (PANSTARRS) is a comet discovered in May 2017 when it was 16 AU / 2.4 billion km further from the Sun , further than the planet Saturn . This was possible because at this point he was already showing significant activity in the form of a coma . It is the most distant active comet from the Sun when it was discovered.

Discovery and observation

C / 2017 K2 was discovered by a team led by Richard J. Wainscoat on shots that on 21 May 2017 as part of the Pan-STARRS -Programms with the 1.8-m - telescope PS1 on Haleakala had been made (Hawaii) . The following day, the discovery was confirmed with further images from the 3.6 m Canada-France-Hawaii Telescope on Mauna Kea . At this point in time the comet showed a brightness of 19 mag, the coma a diameter of 12 ” .

It was subsequently shown that the comet could already be seen on images taken by the Canada-France-Hawaii telescope on May 12, 2013 ( Precovery ), but at that time it had not yet been identified as a comet.

Another six images with a total exposure time of 1,710 seconds were taken on June 27, 2017 with the Wide Field Camera 3 of the Hubble Space Telescope .

Scientific evaluation

Despite its great distance from the Sun, the comet's core was already showing activity in 2013. It is thus the incoming comet furthest from the Sun with an active nucleus - similarly early, but already within Saturn's orbit, only C / 1995 O1 (Hale-Bopp) had been discovered before. In the recordings of the comet from 2013 and 2017, it appears with an almost circular coma. For the size of the comment nucleus, David C. Jewitt and his colleagues determined a maximum radius of 9 km from the brightness profile of the images.

Due to the slow warming of the comet's nucleus from around 10 K in the Oort cloud to currently (2017) around 60–70 K, gases sublime from its surface that carry dust particles with it and thus form the coma cloud. Up to this point, however, there were no signs that the radiation pressure of the sun had an influence on the coma, which would have deformed it or formed a tail . The researchers therefore come to the conclusion that the comet ejects dust particles with a size of at least 0.1 mm and loses 60 kg / s of mass, which is very unusual for a comet beyond Saturn's orbit. From the known sublimation behavior of different gases depending on the distance from the sun to comets, they came to the conclusion that the dust particles are in no case carried away by sublimating water ice , as this sublimates only at a significantly smaller distance from the sun. Instead, it is likely to be super-volatile ice made of frozen carbon dioxide , carbon monoxide , oxygen or nitrogen , similar to what was observed in C / 1980 E1 (Bowell) . Such highly volatile substances were probably present in all comets of the Oort cloud a long time ago. These were released a long time ago from the comets closer to the sun. According to Jewitt, C / 2017 K2 is therefore the most original known comet.

Orbit

The comet is currently (as of July 2020) at a distance of 8.5 AU from the sun, which means that it is moving somewhat within the range of the orbit of Saturn towards the sun. Since its discovery, orbital elements of a currently temporarily hyperbolic orbit have been determined from 2773 observational data over a period of more than seven years . However, the orbit parameters will be able to be determined even more precisely as you get closer to the sun. For this reason, only rough estimates can currently be made of the earlier and future course of the comet's orbit, since the future course in particular can still be significantly changed by non-gravitational forces near the sun. The following information is therefore only to be understood as an evaluation of the currently known path parameters.

The comet's orbit is inclined by around 88 ° to the ecliptic , so it runs almost perpendicular to the planets of the planets. The comet will be the closest point to the Sun ( perihelion ) on 19./20. Passed through December 2022, it is then about 268.8 million km from the Sun and is then even further from the Sun than the planet Mars . During its passage through the inner solar system, the comet experiences a number of relatively close passages of the planets:

Approaches of C / 2017 K2 to planets
date	planet	Min. Distance (in AU )
May 1, 2022	Mars	2.6
May 27, 2022	Saturn	8.6
July 14, 2022	earth	1.8
November 24, 2022	Venus	1.4
February 14, 2023	earth	2.2
March 24, 2023	Mars	2.5
October 15, 2024	Jupiter	2.7
October 15, 2029	Uranus	7.9

Shortly after the discovery of the comet, S. Nakano determined preliminary orbital elements that indicated that the comet originally traveled an elliptical orbit with a semi-major axis of 12,800 AU and will move on one with a semi-major axis of around 850 AU in the future .

According to the currently known orbital elements (as of July 2020), long before it approached the inner solar system, the comet's orbit was elliptical with an eccentricity of around 0.999938 and a semi-major axis of the order of 30,000 AU. The comet came from the Oort cloud and is likely to experience its first passage through the inner solar system as a “dynamic young” comet. Due to the gravitational pull of the planets, especially due to the relatively close passages of Saturn and Jupiter, its orbital eccentricity will decrease to about 0.9980 and its semi-major axis to about 890 AU, so that its orbital period will decrease (without taking into account non-gravitational forces) will shorten to about 26,500 years.

Web links

Commons : C / 2017 K2 (PANSTARRS) - Collection of images, videos and audio files

Individual evidence

↑ ^a ^b ^c ^d D. C. Jewitt, M.-T. Hui, M. Mutchler, H. Weaver, J. Li, J. Agarwal: A Comet Active Beyond the Crystallization Zone. In: The Astrophysical Journal Letters. Vol. 847, 2, 2017, pp. L19: 1–5 doi: 10.3847 / 2041-8213 / aa88b4 . ( PDF; 1.22 MB )
↑ RJ Wainscoat, L. Wells, M. Micheli, H. Sato: Comet C / 2017 K2 (Panstarrs). In: Central Bureau Electronic Telegrams. 4393, 1, 2017 ( bibcode : 2017CBET.4393 .... 1W ).
↑ K. Hille: NASA's Hubble Observes the Farthest Active Inbound Comet Yet Seen. In: Hubble Space Telescope. NASA, October 31, 2017, accessed July 13, 2020 .
↑ C / 2017 K2 (PANSTARRS) in the Small-Body Database of the Jet Propulsion Laboratory (English).
↑ S. Nakano: C / 2017 K2 (PANSTARRS). In: Nakano Note. July 12, 2017, accessed on July 13, 2020 .
↑ SOLEX 12.1 by A. Vitagliano. Retrieved July 9, 2020 .

[ajl-1] D. C. Jewitt, M.-T. Hui, M. Mutchler, H. Weaver, J. Li, J. Agarwal: A Comet Active Beyond the Crystallization Zone. In: The Astrophysical Journal Letters. Vol. 847, 2, 2017, pp. L19: 1–5 doi: 10.3847 / 2041-8213 / aa88b4 . ( PDF; 1.22 MB )

[2] RJ Wainscoat, L. Wells, M. Micheli, H. Sato: Comet C / 2017 K2 (Panstarrs). In: Central Bureau Electronic Telegrams. 4393, 1, 2017 ( bibcode : 2017CBET.4393 .... 1W ).

[3] K. Hille: NASA's Hubble Observes the Farthest Active Inbound Comet Yet Seen. In: Hubble Space Telescope. NASA, October 31, 2017, accessed July 13, 2020 .

[4] C / 2017 K2 (PANSTARRS) in the Small-Body Database of the Jet Propulsion Laboratory (English).

[5] S. Nakano: C / 2017 K2 (PANSTARRS). In: Nakano Note. July 12, 2017, accessed on July 13, 2020 .

[6] SOLEX 12.1 by A. Vitagliano. Retrieved July 9, 2020 .