 P/2019 LD2 (ATLAS) imaged by theHubble Space Telescope in April 2020 | |
| Discovery[1] | |
|---|---|
| Discovered by | A. Fitzsimmons D. Young |
| Discovery site | ATLAS–MLO |
| Discovery date | 10 June 2019 |
| Orbital characteristics[3][4] | |
| Epoch | 31 March 2024 (JD 2460400.5) |
| Observation arc | 5.53 years |
| Earliestprecovery date | 9 May 2018 |
| Number of observations | 748 |
| Aphelion | 5.860 AU |
| Perihelion | 4.537 AU |
| Semi-major axis | 5.199 AU |
| Eccentricity | 0.12724 |
| Orbital period | 11.854 years |
| Inclination | 11.606° |
| 179.43° | |
| Argument of periapsis | 118.24° |
| Mean anomaly | 124.96° |
| Last perihelion | 18 February 2020 |
| Next perihelion | 25 July 2028[2] |
| TJupiter | 2.942 |
| EarthMOID | 3.580 AU |
| JupiterMOID | 0.052 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 aJupiter-family comet andcentaur[7] discovered by theAsteroid Terrestrial-impact Last Alert System on 10 June 2019.[8][9] It was initially reported as the first knownJupiter trojanasteroid to displaycometary activity,[10] but its classification as a Jupiter trojan was retracted after closer examination and a longerobservation arc revealed its orbit to be unstable like a typical Jupiter family comet and implied that its position near the trojans is temporary.[3][11]
P/2019 LD2 was discovered in images by the Asteroid Terrestrial-impact Last Alert System (ATLAS) at theMauna Loa Observatory taken on 10 June 2019.[4] Upon discovery, astronomers Alan Fitzsimmons and David Young atQueen's University Belfast suspected a faintcoma aroundP/2019 LD2.[1] Follow-up observations by theLas Cumbres Observatory in 11 and 13 June 2019 confirmed the cometary appearance ofP/2019 LD2, which now had a more apparent coma and tail. Later observations by the ATLAS-MLO in April 2020 showed thatP/2019 LD2 still retained its cometary appearance, suggesting that it has been continuously active for almost a year.[10]
The discovery ofP/2019 LD2's cometary activity was announced in a press release by theUniversity of Hawaiʻi Institute for Astronomy on 20 May 2020, purporting it as the first known active Jupiter trojan, as it was discovered near Jupiter'sL4Lagrangian point where theGreek camp trojans reside.[10] However, upon closer examination ofP/2019 LD2's orbital dynamics by amateur astronomer Sam Deen,P/2019 LD2 was found to be aJupiter-family comet with a chaotic orbit instead of a Jupiter trojan.[12][11] Subsequently, the comet was reclassified and was given theperiodic comet designationP/2019 LD2 (ATLAS) by theMinor Planet Center on 22 May 2020.[1]
P/2019 LD2 orbits the Sun at a mean distance of 5.29 AU once every 12.18 years. Its orbit has aneccentricity of 0.135 and aninclination of 11.6 degrees with respect to theecliptic.[3] The body'sobservation arc begins with aprecovery, published by thePan-STARRS 1 survey and taken atHaleakala Observatory on 21 May 2018, or 11 months prior to its official discovery observation by the ATLAS-MLO survey.[4]
P/2019 LD2 is a Jupiter-family comet with aTisserand parameter of 2.94, typical for other Jupiter-family comets.[3] The comet's nominal orbit suggests that it is not in a stable 1:1 resonance with Jupiter as it has 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.[3][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 aquasi-satellite cycle with respect to Jupiter that started in 2017 and will end in 2028.[13][14] On 2063 January 23, it will have a very close encounter with Jupiter at 0.016 AU (2.4 million km) orbital predictions after this flyby are rather uncertain.[14]
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 anabsolute magnitude of 12.2.[3] However if the comet displays activity, that can lead to the nucleus size to be overestimated. Archival images byDECam 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 inTajikistan 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[update], no rotationallight curve ofP/2019 LD2 has been obtained fromphotometric observations. The body'srotation period,pole and shape remain unknown.[3][17] The visiblespectrum 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]
2020 in space | ||
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| Space probe launches  |
|   _on_Jul_14_2020_aligned_to_stars.jpg) |
| Impact events | ||
| Selected NEOs | ||
| Exoplanets |
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| Discoveries |
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| Comets | ||
| Space exploration |
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