Английская Википедия:C/2018 F4 (PanSTARRS)

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Шаблон:Infobox planet

C/2018 F4 (PanSTARRS) is a hyperbolic comet (previously classified as A/2018 F4, a hyperbolic asteroid).[1] It was discovered on 17 March 2018 when it was beyond the orbit of Jupiter, Шаблон:Convert from the Sun.[2] It was quite far from the Sun and turned out to simply be an asteroidal object that was discovered before cometary activity was noticeable. As perihelion (closest approach to the Sun) is inside the orbit of Jupiter, this object should become more active. In April 2018 it was determined to be a hyperbolic comet.[3] Given that the incoming velocity was similar to that of an Oort cloud object, we can very confidently say that it is not of interstellar origin.[4][5] C/2018 F4 fragmented around August 2020.[6]

Overview

Файл:C2018 F4-skypath2.png
Path of comet across sky, with 30-day markers, visible over the south pole near perihelion

It would be no problem to fit a parabolic orbit to the C/2018 F4 data,[1]Шаблон:Efn as used to be done for most short arc comets. The orbital eccentricity is decently constrained at Шаблон:Val,Шаблон:Efn so it could even be a closed orbit with an eccentricity below 1.[1] The velocity of the object currently has an uncertainty of ±0.2 km/s. With a common Oort cloud velocity of roughly Шаблон:Convert when inbound 200 AU from the Sun, there is no reason to think 2018 F4 is of interstellar origin.[4]

It will come to perihelion around 3 December 2019 when it will be 3.4 AU from the Sun.[1]

Further observations will be necessary to determine if the orbit is hyperbolic. As a comet this object became known as C/2018 F4 (PANSTARRS).

The somewhat short observation arc of 35 days suggests that before entering the planetary region of the Solar System (epoch 1950), the comet had an orbital period on the order of a hundred thousand years. The heliocentric eccentricity became greater than 1 in November 2016 when the comet was Шаблон:Convert from the Sun.

Inbound velocity at 200 AU from the Sun
compared to Oort cloud objects[7]
Object Year Velocity
km/s		 # of observations
and obs arc
90377 Sedna 1746 Шаблон:Val 196 in 9240 days
C/1980 E1 (Bowell) 1765 Шаблон:Val 179 in 2514 days
C/1997 P2 (Spacewatch) 1779 Шаблон:Val 94 in 49 days
C/2010 X1 (Elenin) 1798 Шаблон:Val 2,222 in 235 days
C/2012 S1 (ISON) 1801 Шаблон:Val 6,514 in 784 days
C/2008 J4 (McNaught) 1855 Шаблон:Val 22 in 15 days
C/2018 F4 1792 Шаблон:Val 402 in 967 days
C/1999 U2 (SOHO) 1947 Шаблон:Val 41 in 1 day
1I/2017 U1 (ʻOumuamua) 1982 Шаблон:Val 121 in 34 days

At 200 AU from the Sun, the escape velocity from the Sun is 2.98 km/s. In the above table, the only outlier is ʻOumuamua with a confident 34-day observation arc. Comet C/2008 J4 (McNaught) has a short observation arc with large uncertainties. Comet C/1999 U2 (SOHO) has a meaningless 1-day observation arc. Comet C/2018 F4 has a common Oort cloud velocity when 200 AU from the Sun.[4]

Notes

Шаблон:Notelist

References

Шаблон:Reflist

External links

Шаблон:Commons category

Шаблон:2018 in space

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  1. ↑ 1,0 1,1 1,2 1,3 Ошибка цитирования Неверный тег <ref>; для сносок jpldata не указан текст
  2. ↑ Ошибка цитирования Неверный тег <ref>; для сносок MPEC2018-F139 не указан текст
  3. ↑ Ошибка цитирования Неверный тег <ref>; для сносок MPEC2018-H21 не указан текст
  4. ↑ 4,0 4,1 4,2 Шаблон:Cite journal
  5. ↑ Шаблон:Cite journal
  6. ↑ Re: fragmentation of comet C/2018 F4 (PANSTARRS)
  7. ↑ Ошибка цитирования Неверный тег <ref>; для сносок Horizons не указан текст
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