(433953) 1997 XR2

(433953) 1997 XR2 is a sub-kilometer sized asteroid, classified as near-Earth object and potentially hazardous asteroid of the Apollo group. It was discovered on 4 December 1997, by the Lincoln Near-Earth Asteroid Research (LINEAR) program at Lincoln Laboratory's Experimental Test Site near Socorro, New Mexico, in the United States.[2]

(433953) 1997 XR2
Discovery [1]
Discovered byLINEAR
Discovery siteLincoln Lab's ETS
Discovery date4 December 1997
Designations
(433953) 1997 XR2
1997 XR2
Apollo · NEO · PHA [1][2]
Orbital characteristics [1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc19.20 yr (7,014 days)
Aphelion1.2924 AU
Perihelion0.8601 AU
1.0762 AU
Eccentricity0.2008
1.12 yr (408 days)
316.19°
0° 52m 58.08s / day
Inclination7.1919°
250.69°
84.604°
Earth MOID0.000135 AU · 0.05 LD
Physical characteristics
Mean diameter
0.2 km (generic)[3]
0.23 km[4]
Mass1.7×1010 kg[4]
20.8[1]

    Orbit and classification

    The asteroid orbits the Sun at a distance of 0.9–1.3 AU once every 13 months (408 days). Its orbit has an eccentricity of 0.20 and an inclination of 7° with respect to the ecliptic.

    It has an Earth minimum orbital intersection distance of 0.000135 AU, which corresponds to 0.05 lunar distances.[1] The body's observation arc begins with its official discovery observation, as no precoveries were taken, and no prior identifications were made.[2]

    Impact risk

    Between 2002 and 2006, 1997 XR2 was considered to have about a 1 in 10,000 chance of colliding with Earth on 1 June 2101, based on a 27-day observation arc following its discovery.[4] With an estimated mass of 1.7×1010 kilograms, it was ranked at level 1 on the Torino scale (0–10) of impact risk, and was the only near-Earth object to be ranked higher than zero until it was joined by 2004 VD17 at level 1 in November 2004, and then when 99942 Apophis – then known only by its provisional designation 2004 MN4 – was temporarily assessed at level four in December 2004. Both 2004 VD17 and 99942 Apophis are now rated at level zero.

    Recovery

    On 24 February 2006, 1997 XR2 was observed by the Mount Lemmon Survey after being lost for more than 8 years.[2] The refinement of its orbit eliminated the possibility of impact in 2101. It is now known that on 20 November 2101, the asteroid will be 0.0392 AU (5,860,000 km) from Earth.[5]

    Physical characteristics

    According to a generic conversion of absolute magnitude to diameter, 1997 XR2 measures 200 to 230 meters.[3][4]

    Naming

    As of 2017, this minor planet remains unnamed.[2]

    References
    1. "JPL Small-Body Database Browser: 433953 (1997 XR2)" (2017-02-16 last obs.). Jet Propulsion Laboratory. Retrieved 2 June 2017.
    2. "433953 (1997 XR2)". Minor Planet Center. Retrieved 1 March 2017.
    3. "Absolute Magnitude (H)". NASA/JPL. Retrieved 1 March 2017.
    4. "1997 XR2 Earth Impact Risk Summary". Wayback Machine. Archived from the original on 7 February 2006. Retrieved 13 January 2013.
    5. "JPL Close-Approach Data: (1997 XR2)" (last observation: 2007-01-15; arc: 9.1 years). Retrieved 3 September 2013.
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