 2020 XL5 imaged by theLowell Discovery Telescope on 2 February 2021 | |
| Discovery[1][2] | |
|---|---|
| Discovered by | Pan-STARRS 1 |
| Discovery site | Haleakala Obs. |
| Discovery date | 12 December 2020 |
| Designations | |
| (614689) 2020 XL5 | |
| 2020 XL5 · P11aRcq[3][4] | |
| Earth trojan[5] · NEO Apollo[6] | |
| Orbital characteristics[6] | |
| Epoch 21 January 2022 (JD 2459600.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 8.88 yr (3,243 days) |
| Earliestprecovery date | 23 December 2012 |
| Aphelion | 1.388AU |
| Perihelion | 0.6133 AU |
| 1.001 AU | |
| Eccentricity | 0.38713 |
| 1.00 yr (365.7 d) | |
| 316.420° | |
| 0° 59m 4.269s / day | |
| Inclination | 13.847° |
| 153.598° | |
| 87.981° | |
| Earth MOID | 0.07571 AU (11,326,000 km) |
| Venus MOID | 0.02726 AU (4,078,000 km)[2] |
| Physical characteristics | |
| 1.18±0.08 km[7] | |
| 0.06±0.03[7] | |
| C[7] | |
| 20–23[2] | |
| 18.58+0.16 −0.15 (r-band)[7] | |
(614689) 2020 XL5 (provisional designation2020 XL5) is anear-Earth asteroid andEarth trojan discovered by thePan-STARRS 1 survey atHaleakala Observatory,Hawaii on 12 December 2020. Itoscillates around theSun–EarthL4Lagrangian point (leading 60°), one of the dynamically stable locations where the combined gravitational force acts through the Sun's and Earth'sbarycenter. Analysis of2020 XL5'strojan orbit stability suggests it will remain around Earth's L4 point for at least four thousand years until gravitationalperturbations from repeated close encounters withVenus destabilize its trojan configuration. With a diameter of about 1.2 km (0.75 mi),2020 XL5 is the second Earth trojan discovered, after(706765) 2010 TK7[7][8] (about 300 m (980 ft) in diameter), and is the largest of its kind known.
2020 XL5 was discovered by thePan-STARRS 1 survey atHaleakala Observatory,Hawaii on 12 December 2020. It was first observed in theconstellationCrater at anapparent magnitude of 21.4.[1] The asteroid was moving at an on-sky rate of 3.02arcseconds per minute, from a distance of 0.68 AU (102 million km; 63 million mi) from Earth.[9]
The asteroid was subsequently listed on theMinor Planet Center'sNear-Earth Object Confirmation Page (NEOCP) as P11aRcq.[4] Over two days, follow-up observations were carried out by theVišnjan Observatory(L01),ESA Optical Ground Station(J04), andCerro Tololo Observatory(807). The asteroid was identified in earlierMount Lemmon Survey(G96) observations from 26 November 2020. The listing was confirmed and publicly announced as2020 XL5 on 14 December 2020.[1]
Thisminor planet was given the permanentnumber 614689 by the Minor Planet Center on 28 March 2022 and is now eligible for naming.[10] In accordance with theInternational Astronomical Union's naming conventions for near-Earth objects,2020 XL5 will be given a mythological name.[11]
The orbit of2020 XL5 is well known with anuncertainty parameter of 0 and a longobservation arc over 8 years. The asteroid has been identified in severalprecovery observations by various sky surveys, including Pan-STARRS, from dates as far back as December 2012.[6][7]
2020 XL5 orbits the Sun at an average distance of 1.001 AU once every365.8 days, or approximately 1Earth year. Its orbit has a higheccentricity of 0.388 and aninclination of 13.8° with respect to theecliptic plane. Over the course of its orbit, its distance from the Sun ranges from 0.61 AU atperihelion to 1.39 AU ataphelion, crossing the orbits ofVenus andEarth. Since its orbit crosses Earth's while having asemi-major axis greater than 1 AU (by a small margin),2020 XL5 is classified as anApollo asteroid.[6]
Trojan objects are most easily conceived as orbiting at aLagrangian point, a dynamically stable location (where the combinedgravitational force acts through the Sun's and Earth'sbarycenter) 60 degrees ahead of (L4) or behind (L5) a massive orbiting body, in a type of 1:1orbital resonance. In reality, they oscillate around such a point.[5]
On 26 January 2021, amateur astronomer Tony Dunn reported that2020 XL5's nominal trajectory appears to be librating about Earth's leading L4 Lagrangian point, suspecting it to be anEarth trojan.[5] Subsequent analysis confirmed modeling stability for at least several thousand years into the future based on existing orbital parameters.[12][13] This would make2020 XL5 more stable than the prototype L4 Earth trojan2010 TK7, which is potentially unstable on timescales of less than 2,000 years.[14] Additional follow-up observations and precoveries confirmed2020 XL5's trojan nature, and showed that it will leave trojan orbit at least 4,000 years into the future.[15][7] Numerical simulations indicate that2020 XL5 has likely been captured into the L4 Langrangian point since the 15th century.[15]
2020 XL5's high orbital eccentricity results in wide,tadpole-shaped oscillation paths in acorotating reference frame with Earth and its Lagrangian points. Although the asteroid crosses Venus's orbit with aminimum orbit intersection distance (MOID) of 0.0273 AU (4.1 million km; 2.5 million mi),[2]perturbations by the planet are currently negligible since its nominal orbit brings it either too high or too low from the plane of Venus's orbit.[16] Venus's influence on2020 XL5's orbit will become greater over time as theirlongitudes of the ascending nodeprecess over hundreds of years, lowering2020 XL5's Venus MOID and eventually destabilizing its trojan orbit by sending it to Earth'sL3 point in several thousand years.[16]
Photometric measurements of optical observations from 2020–2021 show that2020 XL5 exhibits acolor resembling that of carbonaceousC-type asteroids. Based on2020 XL5'sphase curve being similar to C-type asteroids, itsabsolute magnitude (H) of 18.6 corresponds to a mean diameter about 1.18 km (0.73 mi), calculated from ageometric albedo of 0.06 typical for C-type asteroids.[7] This makes2020 XL5 the largest Earth trojan asteroid known to date, being up to three times as large as(706765)2010 TK7 whose size is 0.3 km (0.19 mi).[7]
Because of its fixed position in Earth's sky, relative to the Sun,2020 XL5 is only visible low on the horizon, duringtwilight. Accuratephotometry of itslight curve by terrestrial observers is made erratic by heavyatmospheric distortion and swamped by scattered light from the recently set Sun. Consequently, no information about its rotation has been determined.[7]
Due to2020 XL5's high orbital inclination, arendezvous mission to the asteroid fromlow Earth orbit (LEO) would require a minimum totaldelta-v of 10.3 km/s (6.4 mi/s) – too high to be considered an ideal target for a low-energy trajectory. On the other hand, aflyby trajectory to2020 XL5 from LEO could be more feasible with a minimum total delta-v of 3.3 km/s (2.1 mi/s).[7]
The Trojan asteroid 2020 XL5, which follows the same path around the sun as our planet, was revealed only after a decade of searching.
2020 in space | ||
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