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P/2019 LD2 (ATLAS)

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P/2019 LD2 (ATLAS)
P/2019 LD2 (ATLAS) imaged by the Hubble Space Telescope in April 2020
Discovery[1]
Discovered byAlan Fitzsimmons
David Young
Discovery siteATLAS–MLO
Discovery date10 June 2019
Orbital characteristics[2][3]
Epoch23 September 2020 (JD 2459115.5)
Observation arc5.53 years
Earliest precovery date9 May 2018
Number of
observations		768
Aphelion5.990 AU
Perihelion4.578 AU
Semi-major axis5.284 AU
Eccentricity0.13359
Orbital period12.146 years
Inclination11.568°
179.67°
Argument of
periapsis		123.43°
Mean anomaly13.51°
Last perihelion18 February 2020
Next perihelion25 July 2028[4]
TJupiter2.942
Earth MOID3.580 AU
Jupiter MOID0.051 AU
Physical characteristics[5][6]
Mean diameter
<2.4 km (1.5 mi)
(V–R) = 0.51±0.09
Comet total
magnitude (M1)		7.0
Comet nuclear
magnitude (M2)		12.2
19.0

P/2019 LD2 (ATLAS) is a Jupiter-family comet and centaur[7] discovered by the Asteroid Terrestrial-impact Last Alert System on 10 June 2019.[8][9] It was initially reported as the first known Jupiter trojan asteroid to display cometary activity,[10] but its classification as a Jupiter trojan was retracted after closer examination and a longer observation arc revealed its orbit to be unstable like a typical Jupiter family comet and implied that its position near the trojans is temporary.[2][11]

Discovery

[edit]

P/2019 LD2 was discovered in images by the Asteroid Terrestrial-impact Last Alert System (ATLAS) at the Mauna Loa Observatory taken on 10 June 2019.[3] Upon discovery, astronomers Alan Fitzsimmons and David Young at Queen's University Belfast suspected a faint coma around P/2019 LD2.[1] Follow-up observations by the Las Cumbres Observatory in 11 and 13 June 2019 confirmed the cometary appearance of P/2019 LD2, which now had a more apparent coma and tail. Later observations by the ATLAS-MLO in April 2020 showed that P/2019 LD2 still retained its cometary appearance, suggesting it had been continuously active for almost a year.[10]

The discovery of P/2019 LD2's cometary activity was announced in a press release by the University of Hawaiʻi Institute for Astronomy on 20 May 2020, proposing it as the first known active Jupiter trojan, as it was discovered near Jupiter's L4 Lagrangian point where the Greek camp trojans reside.[10] However, upon closer examination of P/2019 LD2's orbital dynamics by amateur astronomer Sam Deen, P/2019 LD2 was found to be a Jupiter-family comet with a chaotic orbit instead of a Jupiter trojan.[12][11] Subsequently, the comet was reclassified and given the periodic comet designation P/2019 LD2 (ATLAS) by the Minor Planet Center on 22 May 2020.[1]

Orbit and classification

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Animation of P/2019 LD2 around Sun from 1600 to 2200
  Sun ·   Jupiter ·   P/2019 LD2

P/2019 LD2 orbits the Sun at a mean distance of 5.28 AU once every 12.15 years. Its orbit has an eccentricity of 0.134 and an inclination of 11.6 degrees with respect to the ecliptic.[2] The body's observation arc begins with a precovery, published by the Pan-STARRS 1 survey and taken at Haleakala Observatory on 21 May 2018, or 11 months prior to its official discovery observation by the ATLAS-MLO survey.[3]

P/2019 LD2 is a Jupiter-family comet with a Tisserand parameter of 2.92, typical for other Jupiter-family comets.[2] The comet's nominal orbit suggests that it is not in a stable 1:1 resonance with Jupiter as it made a close approach to the planet on 17 February 2017, at a distance of 0.092 AU (13.8 million km; 8.6 million mi), and will make a similarly close approach in 2028.[2][12] Unlike the Jupiter trojans, P/2019 LD2 is 21 degrees ahead of Jupiter, and will continue drifting 30 degrees ahead before returning to Jupiter and making close approaches.[12] P/2019 LD2 is now following what looks like a short arc of a quasi-satellite cycle with respect to Jupiter that started in 2017 and will end in 2028.[13][14] According to a 2021 study, it will have a very close encounter with Jupiter at an uncertain distance on 23 January 2063, possibly as close as 0.016 AU (2.4 million km).[14] Since then, the details of that close approach have been refined somewhat; as of March 2026, JPL gives the minimum and maximum possible close approach distances as 0.052 au and 0.076 au, respectively, and the date as 13 January 2063 (with an uncertainty of ± 1 day), based on data up to 19 November 2023.[2] Orbital predictions after this flyby are uncertain.[14]

Physical characteristics

[edit]
Color composite image of P/2019 LD2 tracked by Gemini North

Based on a generic magnitude-to-diameter conversion,[15] P/2019 LD2 measures approximately 14 kilometers in diameter, for an assumed albedo of 0.12 as the median for small Jupiter trojans,[16] and an absolute magnitude of 12.2.[2] However if the comet displays activity, that can lead to the nucleus size being overestimated. Archival images by DECam from March 2017 indicate that the comet was dimmer than magnitude 23.8 at that time, indicating that the nucleus's radius is less than 1.2 km assuming a 0.05 albedo or less than 0.8 km assuming an 11.2% albedo.[5] Broadband observations taken from the Sanglokh Observatory in Tajikistan suggest a revised upper limit to its radius at approximately 6.1 ± 0.1 km (3.790 ± 0.062 mi).[6]

As of May 2020, no rotational light curve of P/2019 LD2 has been obtained from photometric observations. The body's rotation period, pole and shape remain unknown.[2][17] The visible spectrum does not exhibit any evidence of CN, C2, or C3 emission.[13][14]

During the approach to perihelion in 2020, the comet shed large-grained (0.1 mm typical) dust grains rich with water ice.[13]

See also

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References

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  1. 1 2 3 A. Fitzsimmons; D. Young; et al. (22 May 2020). "Comet P/2019 LD2 (ATLAS)". Minor Planet Electronic Circulars. 2020-K134.
  2. 1 2 3 4 5 6 7 8 "P/2019 LD2 (ATLAS) – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 19 May 2026.
  3. 1 2 3 "P/2019 LD2 Orbit". Minor Planet Center. Retrieved 21 May 2020.
  4. ↑ S. Yoshida (25 March 2025). "P/2019 LD2 (ATLAS)". www.aerith.net. Retrieved 29 June 2025.
  5. 1 2 T. Kareta; L. M. Woodney; C. Schambeau; Y. R. Fernandez; O. H. Pinto; et al. (2021). "Contemporaneous Multiwavelength and Precovery Observations of the Active Centaur P/2019 LD2 (ATLAS)". The Planetary Science Journal. 2 (2): 48. arXiv:2011.09993. Bibcode:2021PSJ.....2...48K. doi:10.3847/PSJ/abe23d.
  6. 1 2 S. Borysenko; G. Kokhirova; F. Rakhmatullaeva (2022). "Some physical properties of a new Jupiter-family comet P/2019 LD2 (ATLAS) from broadband observations". Icarus. 372 114752. arXiv:2111.12810. Bibcode:2022Icar..37214752B. doi:10.1016/j.icarus.2021.114752. S2CID 244584006.
  7. ↑ T. Kareta; K. Volk; J. W. Noonan; et al. (2020). "An Extremely Temporary Co-orbital: The Dynamical State of Active Centaur 2019 LD2". Research Notes of the American Astronomical Society. 4 (5): 74. arXiv:2007.13945. Bibcode:2020RNAAS...4...74K. doi:10.3847/2515-5172/ab963c. S2CID 219739658.
  8. ↑ R. G. Andrews (3 December 2020). "A 'Front-Row Seat' to the Birth of a Comet". The New York Times. Retrieved 4 December 2020.
  9. ↑ J. K. Steckloff; G. Sarid; K. Volk; T. Kareta; et al. (2020). "P/2019 LD2 (ATLAS): An Active Centaur in Imminent Transition to the Jupiter Family". The Astrophysical Journal. 904 (2): L20. arXiv:2008.02943. Bibcode:2020ApJ...904L..20S. doi:10.3847/2041-8213/abc888. S2CID 221083420.
  10. 1 2 3 "UH ATLAS telescope discovers first-of-its-kind asteroid". Institute for Astronomy. University of Hawaiʻi. 20 May 2020. Archived from the original on 23 May 2020. Retrieved 21 May 2020.
  11. 1 2 "Astronomers recategorize asteroid-like comet detected by UH ATLAS telescope". University of Hawaiʻi. 26 May 2020. Retrieved 27 May 2020.
  12. 1 2 3 J. Hecht (28 May 2020). "Jupiter Has Trapped a Comet in a Bizarre Orbit". Sky & Telescope. Retrieved 29 May 2020.
  13. 1 2 3 B. T. Bolin; Y. R. Fernandez; C. M. Lisse; T. R. Holt; Z. Y. Lin; et al. (2021). "Initial Characterization of Active Transitioning Centaur, P/2019 LD2 (ATLAS), Using Hubble, Spitzer, ZTF, Keck, Apache Point Observatory, and GROWTH Visible and Infrared Imaging and Spectroscopy". The Astronomical Journal. 161 (116): 116. arXiv:2011.03782. Bibcode:2021AJ....161..116B. doi:10.3847/1538-3881/abd94b. S2CID 234356588.
  14. 1 2 3 4 J. Licandro; J. de Leon; F. Moreno; C. de la Fuente Marcos; R. de la Fuente Marcos; et al. (2021). "Activity of the Jupiter co-orbital comet P/2019 LD2 (ATLAS) observed with OSIRIS at the 10.4 m GTC". Astronomy and Astrophysics. 650: 79–89. arXiv:2103.14613. Bibcode:2021A&A...650A..79L. doi:10.1051/0004-6361/202038842. S2CID 232380303.
  15. ↑ D. Bruton. "Conversion of Absolute Magnitude to Diameter for Minor Planets". Department of Physics, Engineering, and Astronomy. Stephen F. Austin State University. Archived from the original on 23 July 2011. Retrieved 21 May 2020.
  16. ↑ Y. R. Fernández; D. C. Jewitt; J. E. Ziffer (2009). "Albedos of Small Jovian Trojans". The Astronomical Journal. 138 (1): 240–250. arXiv:0906.1786. Bibcode:2009AJ....138..240F. doi:10.1088/0004-6256/138/1/240. S2CID 5592793.
  17. ↑ "LCDB Data for 2019 LD2 – Not in Data Base". Asteroid Lightcurve Database (LCDB). Retrieved 21 May 2020.
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