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C/2014 UN271 (Bernardinelli–Bernstein)

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C/2014 UN271 (Bernardinelli-Bernstein)
Discovery image of C/2014 UN271 from the Dark Energy Survey
Discovery
Discovered byPedro Bernardinelli
Gary Bernstein
(Dark Energy Survey)
Discovery date20 October 2014
(first discovery image)
Designations
2014 UN271
Orbital characteristics
Epoch3 August 2016
(JD 2457603.5)[a]
Number of
observations		82[5]
Orbit typeOort cloud
Aphelion≈ 40,000 AU (inbound)[1]
≈ 54,000 AU (outbound)[b]
Perihelion10.95 AU[2]
Semi-major axis≈ 20,000 AU (inbound)[3][1]
≈ 27,000 AU (outbound)
Eccentricity0.99944 (inbound)[1]
1.0003 (2016)[4]
1.0007 (perihelion)[5]
0.99960 (outbound)[1]
Orbital period≈ 3 million yr (inbound)[1]
≈ 4.5 million yr (outbound)
Inclination95.568°
Next perihelion≈ 23 January 2031[c][2]
TJupiter–0.398[4]
Jupiter MOID6.174 AU[4]
Physical characteristics
Dimensions100–200 km[6] (assumed albedo 0.04-0.10)
Comet total
magnitude (M1)		6.7±0.7[4]
Comet nuclear
magnitude (M2)		7.802±0.256 (assumed)[4]

C/2014 UN271 (Bernardinelli-Bernstein), or simply 2014 UN271, is a potentially large Oort cloud comet discovered by astronomers Pedro Bernardinelli and Gary Bernstein in archival images from the Dark Energy Survey.[7][8] When first imaged in October 2014, the object was 29 AU (4.3 billion km) from the Sun and almost as far as Neptune's orbit. As of 2021, it is currently approaching the Sun at a distance of 20.2 AU (3.0 billion km) and will reach its perihelion of 10.9 AU (just outside of Saturn's orbit) in January 2031.[4]

Nomenclature

The object was initially given the minor planet provisional designation 2014 UN271, where 2014 is when the first discovery image was taken, U is the discovery half-month (2nd half of October), and N271 is the discovery counter in that half-month. Following the confirmation of cometary activity by the Minor Planet Center, the object was given its official cometary designation C/2014 UN271 (Bernardinelli-Bernstein), with the C/ prefix indicating a non-periodic orbit.[9]

Observations

C/2014 UN271's absolute magnitude in its discovery images was 7.8.[10]. Assuming it had an asteroidal appearance at that time, this suggested that its nucleus was around 100 km in diameter. However, if cometary activity was present at the time of the original observations, it would be significantly smaller.[11] On 22 June 2021, cometary activity was observed and reported by Tim Lister at the Las Cumbres Observatory's telescope in Sutherland, South Africa and Luca Buzzi at the SkyGems Remote Telescope in Namibia.[12][13][9] The object's heliocentric distance was 20.18 AU (3.0 billion km) and it was observed to be brighter than predicted, with a slightly elongated coma reported by SkyGems to be approximately 15 arcseconds wide.[12][13] The comet is suspected to have been active at 23.8 AU (3.6 billion km) and may have been active at 29 AU (4.3 billion km) which suggests the comet nucleus is significantly smaller than early estimates.[14] Cometary activity has previously been observed as far as 25.8 AU (3.9 billion km) from the Sun on a few comets, for example C/2010 U3 (Boattini).[15] Cometary activity at these distances can be generated by supervolatiles such as CO and CO2.

Orbit

Orbit diagram of C/2014 UN271

With an observation arc of several years using dozens of observations, the orbit of C/2014 UN271 is securely known.[d] Its incoming orbit in 1950, as calculated by JPL Horizons, has a semimajor axis of 20,000 AU (0.3 ly). This indicates that C/2014 UN271 was at its furthest distance, or aphelion, of 40,000 AU (0.6 ly) in the Oort cloud around 1.5 million years ago.[1][a][e] It will come to perihelion (closest approach to the Sun) around 23 January 2031 at a distance of 10.95 AU[2] which is just outside of Saturn's orbit. It will make its closest approach to Earth around 5 April 2031 at a distance of 10.11 AU.[16] It will cross the ecliptic plane in August 2033 when it is outbound ~12 AU from the Sun. Its outbound orbital period will be approximately 4.5 million years with an aphelion distance of about 54,000 AU (0.9 ly).[1] The object is only very loosely bound to the Sun and subject to perturbations by the galactic tide while in the Oort cloud.

With a current declination of −47°, it is best seen from the Southern hemisphere. Its cometary activity and evolution will be monitored by the Vera Rubin Observatory as it approaches perihelion.[17] Once at perihelion, the comet is not expected to get brighter than Pluto (mag 13–16) and is more likely to reach the brightness of Pluto's moon Charon (mag 16.8) as the comet does not enter the inner Solar System where comets become notably more active.[18][19] Even if it reaches the magnitude of Pluto, it will require about a 200 mm telescope to be visually seen.[20] The similarly-sized centaurs 2060 Chiron and 5145 Pholus both come closer to the Sun than C/2014 UN271 will.

Comets from the outer Oort Cloud
Comet Inbound
Epoch 1950
Barycentric
Aphelion
(AU) 		Outbound
Epoch 2050
Barycentric
Aphelion
(AU)
C/1980 E1 (Bowell) 75,000 hyperbolic
C/1999 F1 (Catalina) 54,000 66,000
C/2003 A2 (Gleason) 47,000 15,000
C/2006 P1 (McNaught) 67,000 4,100
C/2010 U3 (Boattini) 34,000 9,900
C/2011 L4 (PANSTARRS) 68,000 4,500
Comet ISON hyperbolic hyperbolic
C/2013 A1 (Siding Spring) 52,000 13,000
C/2013 US10 (Catalina) 38,000 hyperbolic
C/2014 UN271 (Bernardinelli-Bernstein) 40,000 54,000[b]
C/2017 K2 (PANSTARRS) 50,000 1,800
C/2017 T2 (PANSTARRS) 74,000 3,000

See also

Notes

  1. ^ a b For epoch 1950-Jan-01 orbit period is "PR= 1.01E+09 / 365.25 days" = ~2.8 million years. In 1950 the comet was still 95 AU from the Sun and had not entered the planetary region of the Solar System.
  2. ^ a b For epoch 2100-Jan-01 orbit period is "PR= 1.63E+09 / 365.25 days" = ~4.46 million years. In 2100 the comet will be 84 AU from the Sun and will have exited the planetary region of the Solar System.
  3. ^ Perihelion passage: Given perihelion is still 10 years away and the orbit is highly eccentric, an epoch closer to 2031 will give a more accurate estimated perihelion date that better accounts for continuing planetary perturbations. The JPL SBDB's epoch 2016 unperturbed two-body solution (Sun+comet) gives a date of 2031-Jan-21. But properly integrating the orbit with JPL Horizons to perihelion passage accounts for all planetary perturbations and gives a date of 2031-Jan-23.
  4. ^ JPL 1 (4 year arc) defined at epoch 2021-Jul-01 had aphelion (Q) = ~14,300 AU and period = ~604,000 years. The current orbit (6 year arc) defined at epoch 2021-Jul-01 also has aphelion (AD) = 14,300 AU and period = ~602,000 years. The solutions are basically the same.
  5. ^ While a loosely bound long-period comet such as C/2014 UN271 is in the planetary region of the Solar System at an epoch defined near the present year, the JPL SBDB can show a misleading orbital period such as ~600000 years that does not display the true inbound or outbound orbital period or true aphelion distances. The orbit of a long-period comet is properly obtained when the osculating orbit is computed at an epoch before and/or after leaving the planetary region. Using an epoch of 1950 (inbound) and 2100 (outbound) will generate much more meaningful results.

References

  1. ^ a b c d e f g "JPL Horizons On-Line Ephemeris for 2014 UN271 at epoch 1950 and 2100". JPL Horizons On-Line Ephemeris System. Jet Propulsion Laboratory. Retrieved 19 June 2021. Solution using the Solar System Barycenter. Ephemeris Type:Elements and Center:@0 (To be outside planetary region, inbound epoch 1950 and outbound epoch 2100. Aphelia/orbital periods defined while in the planetary-region are misleading for knowing the long-term inbound/outbound solutions.)
  2. ^ a b c "Perihelion in January 2031" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Retrieved 20 June 2021.
  3. ^ Bernardinelli, Pedro [@phbernardinelli] (20 June 2021). "our a (semi-major axis) is 20,500+-300 au" (Tweet). Retrieved 22 June 2021 – via Twitter.
  4. ^ a b c d e f "JPL Small-Body Database Browser: (2014 UN271)" (2021-06-22 last obs.). Jet Propulsion Laboratory. Retrieved 19 June 2021.
  5. ^ a b "2014 UN271". Minor Planet Center. Retrieved 19 June 2021.
  6. ^ "The Largest Comet Ever Found Is Making Its Move Into a Sky Near You". New York Times. 28 June 2021. Retrieved 1 July 2021.
  7. ^ "MPEC 2021-M53 : 2014 UN271". Minor Planet Electronic Circulars. Minor Planet Center. 19 June 2021. Retrieved 19 June 2021.
  8. ^ Kocz, Amanda (25 June 2021). "Giant Comet Found in Outer Solar System by Dark Energy Survey". NOIRLab. Retrieved 25 June 2021.
  9. ^ a b "MPEC 2021-M83 : COMET C/2014 UN271 (Bernardinelli-Bernstein)". Minor Planet Electronic Circulars. Minor Planet Center. 24 June 2021. Retrieved 24 June 2021.
  10. ^ "Archive of JPL #1 (solution date: 2021-Jun-21)". Jet Propulsion Laboratory. 21 June 2021.
  11. ^ Schwamb, Meg [@megschwamb] (20 June 2021). "We're assuming we're measuring the brightness of the object with no contribution from a dust coma. It will be smaller if there is a coma. [...]" (Tweet). Retrieved 22 June 2021 – via Twitter.
  12. ^ a b Kokotanekova, Rosita; Lister, Tim; Bannister, Michele; Snodgrass, Colin; Opitom, Cyrielle; Schwamb, Meg; Kelley, Michael S. P. (22 June 2021). "Newly discovered object 2014 UN271 observed as active at 20.18 au". The Astronomer's Telegram. Retrieved 22 June 2021.
  13. ^ a b "2014 UN271: cometary activity". MPML @ groups.io. Retrieved 22 June 2021.
  14. ^ Farnham, Tony (6 July 2021). "Comet C/2014 UN271 (Bernardinelli-Bernstein) exhibited activity at 23.8 au". The Astronomer's Telegram. Retrieved 6 July 2021.
  15. ^ Hui, Man-To; Farnocchia, Davide; Micheli, Marco (2019). "C/2010 U3 (Boattini): A Bizarre Comet Active at Record Heliocentric Distance". The Astronomical Journal. 157 (4): 162. arXiv:1903.02260. doi:10.3847/1538-3881/ab0e09.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  16. ^ "Closest Approach to Earth 2031" (Closest Earth approach occurs when deldot flips from negative to positive). JPL Horizons. Retrieved 25 June 2021.
  17. ^ Gater, Will (24 June 2021). "Huge Oort Cloud object has been spotted entering the solar system". PhysicsWorld. Retrieved 24 June 2021.
  18. ^ Irving, Michael (20 June 2021). "Extremely eccentric minor planet to visit inner solar system this decade". New Atlas. Retrieved 21 June 2021.
  19. ^ Williams, David (25 November 2020). "Pluto Fact Sheet". NASA. Retrieved 21 June 2021.
  20. ^ Johnson-Roehr (4 July 2021). "See Pluto in 2015". Sky & Telescope. Retrieved 4 July 2021.

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