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C/2022 E3 (ZTF)

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C/2022 E3 (ZTF)
C/2022 E3 (ZTF) on 27 January 2023.
Discovery
Discovered byZwicky Transient Facility
Discovery date2 March 2022[1]
Orbital characteristics
Observation arc456 days
Number of
observations		3382
Orbit typeLong-period comet
Aphelion≈2800 AU (barycentric epoch 1950)[2]
Perihelion1.112 AU[3]
Eccentricity1.00002 (heliocentric epoch 2495)[4]
0.999992 (barycentric epoch 2050)[2]
Orbital period≈50,000 yr (inbound)[2]
Ejection or many millions of years (outbound)
Inclination109.17°
Last perihelion12 January 2023[3]
Earth MOID0.221 AU (33.1 million km)[3]
Jupiter MOID1.743 AU (260.7 million km)
Physical characteristics
Dimensions≈1 km[5]
Comet total
magnitude (M1)		10.5±0.6[3]

C/2022 E3 (ZTF) is a long-period comet from the Oort cloud that was discovered by the Zwicky Transient Facility (ZTF) on 2 March 2022.[1] The comet has a bright green glow around its nucleus, due to the effect of sunlight on diatomic carbon and cyanogen.[6][5]

The comet's systematic designation starts with C to indicate that it is not a periodic comet, and "2022 E3" means that it was the third comet to be discovered in the first half of March 2022.[5]

The comet nucleus was estimated to be about a kilometre in size, rotating every 8.7 hours.[7][8] Its tails of dust and gas extended for millions of kilometres and, during January 2022, a third anti-tail was visible.[9]

The comet reached its perihelion on 12 January 2023, at a distance of 1.11 AU (166 million km; 103 million mi), and the closest approach to Earth was on 1 February 2023, at a distance of 0.28 AU (42 million km; 26 million mi). The comet reached magnitude 5 and is visible with the naked eye under moonless dark skies.[10][11][12][13]

Observational history

Astronomers Bryce Bolin and Frank Masci discovered C/2022 E3 (ZTF) using the Zwicky Transient Facility (ZTF) survey on 2 March 2022.[1] Upon discovery the comet had an apparent magnitude of 17.3 and was about 4.3 AU (640 million km; 400 million mi) from the Sun. The object was initially identified as an asteroid, but subsequent observations revealed it had a very condensed coma, indicating it is a comet.[1][14]

By early November 2022, the comet had brightened to magnitude 10 and was appearing to move slowly in Corona Borealis and Serpens as it moved parallel to Earth.[15] The comet exhibited a green coma and a yellowish dust tail and a faint ion tail. The comet was visible in the early evening and started being visible in the morning sky by the end of November.[16] By 19 December, the comet had developed a greenish coma, short, broad dust tail, and long faint ion tail stretching across a 2.5-degree wide field of view.[17] After that, the comet started moving northward, passing through Boötes, Draco, and Ursa Minor, passing within about 10 degrees of Polaris by the end of January.[16][18]

The comet reached its perihelion on 12 January 2023, at a distance of 1.11 AU (166 million km; 103 million mi).[19][20] The first naked eye observations of the comet occurred on 16 and 17 January, with the comet having an estimated magnitude of 5.4 and 6.0 respectively.[21] Strong solar wind from a coronal mass ejection caused a disconnection event of the ion tail of the comet on 17 January, making it appear broken.[22] On 22 January an antitail became visible. This tail appears pointing toward the Sun and opposite the dust and ion tails. It is caused by particles lying on a disk on the orbital plane of the comet, and when Earth aligns with that plane, they look like a reverse tail.[23][24]

The comet's closest approach to Earth was on 1 February 2023, at a distance of 0.28 AU (42 million km; 26 million mi). As of 31 January 2023, the comet has an apparent magnitude of about 5; its coma is reported to be about 20' across.[10] During its closest approach to Earth it will appear near the north celestial pole[25] and be located within the Camelopardalis constellation.[26] The moon is now waxing gibbous and the brightening moon hampers viewing the comet without optical aid.[27] On 5 February, at the full moon, the comet will pass 1.5 degrees from the bright star Capella.[27] On 10 to 11 February, the comet will pass 1.5 degrees from Mars and, on 13 to 15 February, will pass in front of the Hyades star cluster.[16]

Positions of the comet C/2022 E3 (ZTF) in the starry sky between 14 January and 16 February 2023

C/2022 E3 closest Earth approach on 2023-Feb-01 17:55 UT[3]
Date & time of
closest approach 		Earth distance
(AU) 		Sun distance
(AU) 		Velocity
wrt Earth
(km/s) 		Velocity
wrt Sun
(km/s) 		Uncertainty
region
(3-sigma) 		Lunar
elongation 		Lunar
phase 		Reference
2023-02-01 17:55 0.2839 AU (42.47 million km; 26.39 million mi; 110.5 LD) 1.159 AU (173.4 million km; 107.7 million mi; 451 LD) 57.4 39.1 ± 500 km 44° 86% Horizons

Color

The green color is likely due to the presence of diatomic carbon, chiefly around the comet's head.[28] The C2 molecule, when excited by the solar ultraviolet radiation, emits mostly in infrared, but its triplet state radiates at 518 nm (nanometers). It is produced by photolysis of organic materials evaporated from the nucleus. It then undergoes photodissociation, with a lifetime of about two days, at which time the green glow appears in the comet's head but not the tail.[29][30] The comet researcher Matthew Knight opined that the green color of this comet is not unusual for comets with a higher gas content, but they only rarely approach the Earth as close so it provides for very good observation of the greenish hue.[31]

Outbound trajectory

JPL Horizons shows the barycentric outbound orbit to be bound to the Sun+Jupiter system at an epoch in the year 2050, but with an unrealistic maximum distance of 270,000 AU (4.3 ly) which is beyond the Oort cloud.[2] Using a heliocentric orbit at epoch 2495 with just the Sun's mass shows the comet unbound to the Solar System, but an epoch of 2499 shows it bound.[4] The comet will either leave the Solar System altogether or return in many millions of years depending on perturbations from outgassing or perturbations while in the Oort cloud.[32]

Comparable objects

Diffuse objects visible to the naked eye
Object apmag
Andromeda Galaxy (M31) 3.4
Orion Nebula (M42) 4
C/2022 E3 (ZTF) 5
Triangulum Galaxy (M33) 5.7
Wikimedia Commons has media related to C/2022 E3 (ZTF).
  • The comet in December 2022, from the Asiago Astrophysical Observatory
    The comet in December 2022, from the Asiago Astrophysical Observatory
  • The comet on 10 January 2023 by Andrea Reguitti of the University of Padua
    The comet on 10 January 2023 by Andrea Reguitti of the University of Padua
  • The comet on 20 January 2023, showing a broad dust tail and a thin ion tail
    The comet on 20 January 2023, showing a broad dust tail and a thin ion tail
  • The comet on 22 January 2023, with the antitail visible
    The comet on 22 January 2023, with the antitail visible
  • The comet on 28 January 2023, with star trails due to its relative motion in the sky
    The comet on 28 January 2023, with star trails due to its relative motion in the sky

References

  1. ^ a b c d Bolin, B.; et al. (21 March 2022). "MPEC 2022-F13 : COMET C/2022 E3 (ZTF)". Minor Planet Electronic Circular. Minor Planet Center. Archived from the original on 25 March 2022. Retrieved 24 August 2022.
  2. ^ a b c d Horizons output. "Barycentric Osculating Orbital Elements for Comet C/2022 E3 (ZTF)". Archived from the original on 15 January 2023. Retrieved 24 August 2022. (Solution using the Solar System's barycenter (Sun+Jupiter). Select Ephemeris Type:Elements and Center:@0) Epoch 1950 has PR= 1.887E+07 / 365.25 = 51700 years
  3. ^ a b c d e "JPL Small-Body Database Browser: C/2022 E3". JPL. Archived from the original on 19 January 2023. Retrieved 24 August 2022.
  4. ^ a b Horizons output. "Heliocentric Osculating Orbital Elements for Comet C/2022 E3 (ZTF) still near 1.0 and chaotic in epoch 2495+".
  5. ^ a b c "A rare green comet is becoming visible in northern skies. How to see it without a telescope". www.usatoday.com. Retrieved 2 February 2023.
  6. ^ Georgiou, Aristos (10 January 2023). "What makes the green comet green?". Newsweek. Archived from the original on 25 January 2023. Retrieved 25 January 2023.
  7. ^ "Once in 50,000-year comet may be visible to the naked eye". France 24. 7 January 2023. Retrieved 2 February 2023.
  8. ^ "ATel #15879: Rotation period of comet C/2022 E3 ZTF from CN morphology". The Astronomer's Telegram. 30 January 2023. Retrieved 2 February 2023.
  9. ^ "Understanding the Tails of Comet ZTF (C/2022 E3)". Sky & Telescope. 1 February 2023. Retrieved 2 February 2023.
  10. ^ a b "COBS: Comet C/2022 E3 (ZTF) observation list". Archived from the original on 1 February 2023. Retrieved 31 January 2023.
  11. ^ "Circumpolar Comet ZTF (C/2022 E3) is Here!". Sky & Telescope. 16 January 2023. Archived from the original on 17 January 2023. Retrieved 17 January 2023.
  12. ^ Hall, Shannon (20 January 2023). "How to Watch the 'Green Comet' in Night Skies". The New York Times. Archived from the original on 20 January 2023. Retrieved 21 January 2023.
  13. ^ Mack, Eric (23 January 2023). "Bright Green Comet Passing Earth Is Visible Now in Dark Skies". CNET. Archived from the original on 23 January 2023. Retrieved 24 January 2023.
  14. ^ "Electronic Telegram No. 5111- COMET C/2022 E3 (ZTF)". Central Bureau for Astronomical Telegrams. 21 March 2022. Archived from the original on 17 September 2022. Retrieved 24 August 2022.
  15. ^ Ratcliffe, Martin; Ling, Alister (1 November 2022). "Sky This Month: November 2022". Astronomy. Archived from the original on 10 November 2022. Retrieved 4 November 2022.
  16. ^ a b c King, Bob (17 November 2022). "Sneak Peek at Two Promising Comets". Sky & Telescope. Archived from the original on 12 November 2022. Retrieved 18 November 2022. {{cite web}}: |archive-date= / |archive-url= timestamp mismatch; 12 December 2022 suggested (help)
  17. ^ "Comet 2022 E3 (ZTF) | Science Mission Directorate". NASA. 24 December 2022. Archived from the original on 30 December 2022. Retrieved 31 December 2022.
  18. ^ Atkinson, Stuart (30 January 2023). "How to see the Green Comet C/2022 E3 (ZTF) in the sky". BBC Sky at Night. Archived from the original on 11 January 2023. Retrieved 30 January 2023.
  19. ^ Machholz, Donald (25 March 2022). "EarthSky | New comet might brighten enough for binoculars". Earth & Sky. Archived from the original on 18 January 2023. Retrieved 24 August 2022.
  20. ^ Atkinson, Stuart (7 December 2022). "Comet C/2022 E3 (ZTF) is one to watch out for in December and January". BBC Sky at Night. Archived from the original on 11 January 2023. Retrieved 10 December 2022.
  21. ^ "COBS - Comet OBServation database". cobs.si. Archived from the original on 18 January 2023. Retrieved 18 January 2023.
  22. ^ Pultarova, Tereza (19 January 2023). "Brilliant green comet loses part of its tail to solar storm in this stunning astrophotographer photo". Space.com. Archived from the original on 22 January 2023. Retrieved 22 January 2023.
  23. ^ Thomson, Jess (23 January 2023). "Green comet ZTF develops strange "anti-tail" pointing in wrong direction". Newsweek. Archived from the original on 24 January 2023. Retrieved 24 January 2023.
  24. ^ Tingley, Brett (23 January 2023). "How to see the green comet C/2022 E3 (ZTF) visible in the night sky now as it approaches Earth". Space.com. Archived from the original on 23 January 2023. Retrieved 24 January 2023.
  25. ^ King, Bob (30 March 2022). "Comets to View in 2022". Sky & Telescope. Archived from the original on 7 January 2023. Retrieved 24 August 2022.
  26. ^ Urbain, Tom (10 November 2022). "Starlust.org | Meet Comet C/2022 E3 (ZTF), the next naked-eye comet in the night sky". StarLust. Archived from the original on 12 January 2023. Retrieved 10 November 2022.
  27. ^ a b King, Bob (27 January 2023). "See Comet ZTF (C/2022 E3) Dash Between Big and Little Dippers". Sky & Telescope. Archived from the original on 29 January 2023. Retrieved 30 January 2023.
  28. ^ Rao, Joe (6 January 2023). "A comet not seen in 50,000 years is coming. Here's what you need to know". Space.com. Archived from the original on 6 January 2023. Retrieved 6 January 2023.
  29. ^ Krämer, Katrina (23 December 2021). "Comets' green colour comes from dicarbon dissociation, experiments confirm". Chemistry World. Archived from the original on 26 November 2022. Retrieved 7 January 2023.
  30. ^ Koe, Crystal (31 January 2022). "Why are comet heads green — but not their tails?". Massachusetts Institute of Technology. Archived from the original on 7 January 2023. Retrieved 7 January 2023.
  31. ^ Greshko, Michael (1 February 2023). "A green comet is passing by Earth. Here's how to see it". National Geographic. Archived from the original on 1 February 2023. Retrieved 2 February 2023.
  32. ^ Brandon Spektor (19 January 2023). "Green comet C/2022 E3 will make its closest approach to Earth in 50,000 years this week. Here's how to watch". Live Science. Archived from the original on 1 February 2023. Retrieved 1 February 2023.
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