2014 XL7

2014 XL7 is a near-Earth object and Apollo asteroid, approximately 230 meters (750 feet) in diameter. It was the most dangerous potentially hazardous asteroid on Sentry Risk Table upon its discovery by the Mount Lemmon Survey in December 2014.[7] At the time, the asteroid had a cumulative 1 in 83000 chance of impacting Earth on 4–5 June between the years 2048 and 2084.[4] After the object's observation arc had been extended to 35 days, it was removed from the Sentry Risk Table on 15 January 2015.[8] Since then the asteroid's orbit has been secured. Although it has an Earth minimum orbit intersection distance of less than one lunar distance, there are no projected close encounters with Earth in the foreseeable future, with its closest passage to occur in May 2046, still millions of kilometers away.[9]

2014 XL7
Discovery[1][2]
Discovered byMLS
Discovery siteMount Lemmon Obs.
Discovery date11 December 2014
Designations
2014 XL7
Orbital characteristics[3]
Epoch 1 July 2021 (JD 2459396.5)
Uncertainty parameter 2[2][3]
Observation arc1.95 yr (713 d)
Aphelion2.5362 AU
Perihelion0.7719 AU
1.6540 AU
Eccentricity0.5333
2.13 yr (777 d)
80.070°
0° 27m 47.88s / day
Inclination7.5019°
74.478°
250.76°
Earth MOID0.00217 AU (0.84 LD)
Physical characteristics
Mean diameter
25.82[6]
21.0[2][3]

    Discovery

    On 1 September 2014, the asteroid passed about 0.259 AU (38,700,000 km; 24,100,000 mi) from Earth,[9] but remained undetected as at that time the asteroid had an apparent magnitude of 25 and was roughly 25° from the Sun.[10] It was discovered on 11 December 2014, by the Mount Lemmon Survey at an apparent magnitude of 20 using the Steward Observatory's 1.52-meter (60 in) reflecting telescope at Mount Lemmon Observatory near Tucson, Arizona, and received the provisional designation 2014 XL7.[1]

    Palermo Scale rating

    With an observation arc of only 19 days, it had a cumulative Palermo Scale rating of –2.85 and was briefly the 9th most dangerous asteroid known.[7] It was calculated that on 4 June 2065, there was a 1 in 270,000 chance of impact and on 4 June 2076, there was a 1 in 137,000 chance of impact.[4] On 15 January 2015, the asteroid was recovered by Cerro Paranal Observatory which extended the observation arc to 35 days,[2] and 2014 XL7 was subsequently removed from the Sentry Risk Table using JPL solution 9.[8]

    Orbit and classification

    As of 2021, and last observed in November 2016, the asteroid has a better constrained orbit with an observation arc of 713 days and an uncertainty parameter of 2, which ranges from 0 (good) to 9 (highly uncertain).[2][3] It has an apparent magnitude of 25.82,[6] and orbits the Sun at a distance of 0.77–2.5 AU once every 2 years and 2 months (777 days; semi-major axis of 1.65 AU). Its orbit has an eccentricity of 0.53 and an inclination of 8° with respect to the ecliptic.[3] The potentially hazardous asteroid has a minimum orbit intersection distance with Earth of 0.00217 AU (325,000 km; 0.844 LD), or less than the distance to the Moon. Its closest encounter with Earth will occur on 29 May 2046, at a nominal distance of 13,875,000 km; 8,622,000 mi (0.09275 AU).[9] With an absolute magnitude of 21,[3] the asteroid is approximately 170–380 meters (560–1,200 feet) in diameter.[5][lower-alpha 1]

    Notes
    1. The object's average reflectivity is unknown. As near-Earth asteroids may have an albedo between 0.24 and 0.05 for objects with a relatively bright siliceous and dark carbonaceous composition, respectively, an estimated mean-diameter in the range of 170–380 meters (560–1,200 feet) should assumed.

    References
    1. "MPEC 2014-X76 : 2014 XL7". Minor Planet Electronic Circular. IAU Minor Planet Center. 15 December 2014. Retrieved 7 September 2021. (K14X07L)
    2. "2014 XL7". Minor Planet Center. Retrieved 7 September 2021.
    3. "JPL Small-Body Database Browser: (2014 XL7)" (2016-11-23 last obs.). Jet Propulsion Laboratory. Retrieved 7 September 2021.
    4. "Earth Impact Risk Summary: 2014 XL7". WayBack Machine: NASA/JPL Near-Earth Object Program Office. 31 December 2014. Archived from the original on 31 December 2014. Retrieved 1 January 2015.
    5. "Asteroid Size Estimator". CNEOS NASA/JPL. Retrieved 7 September 2021.
    6. "Asteroid 2014 XL7 – Ephemerides". NEODyS-2, Near Earth Objects – Dynamic Site. Retrieved 7 September 2021.
    7. "Sentry Risk Table". WayBack Machine: NASA/JPL Near-Earth Object Program Office. 31 December 2014. Archived from the original on 31 December 2014. Retrieved 1 January 2015. (PS=–2.85)
    8. "Date/Time Removed". NASA/JPL Near-Earth Object Program Office. Archived from the original on 2 June 2002. Retrieved 7 September 2021.
    9. "SBDB Close-Approach Data: (2014 XL7)" (last observation: 2016-11-23; arc: 713 days). Jet Propulsion Laboratory. Retrieved 7 September 2021.
    10. "2014XL7 Ephemerides for 1 September 2014". NEODyS (Near Earth Objects – Dynamic Site). Retrieved 1 January 2015.
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