| Discovery[1] | |
|---|---|
| Discovered by | LONEOS |
| Discovery site | Anderson Mesa Stn. |
| Discovery date | 3 August 1998 |
| Designations | |
| (31345) 1998 PG | |
| 1998 PG | |
| NEO · Amor[1][2] | |
| Orbital characteristics[1] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 38.54 yr (14,075 days) |
| Aphelion | 2.8048AU |
| Perihelion | 1.2277 AU |
| 2.0162 AU | |
| Eccentricity | 0.3911 |
| 2.86yr (1,046 days) | |
| 215.36° | |
| 0° 20m 39.48s / day | |
| Inclination | 6.5013° |
| 222.74° | |
| 156.11° | |
| Knownsatellites | 1[3][4][5][a] |
| Earth MOID | 0.2354 AU · 91.7LD |
| Physical characteristics | |
| Dimensions | 0.880 km(derived)[6] 0.9±0.2 km[5][a] 0.940±0.21(derived)[4] |
| 2.5h[7] 2.51620±0.00003 h[3] | |
| 0.18[5][a] 0.20(assumed)[6] | |
| SMASS = Sq[1] · S[6] B–V =0.810±0.020[3] V–R =0.440±0.010[3] V–I =0.760±0.020[3] | |
| 17.3[1] · 17.64±0.14[3][6][8] | |
(31345) 1998 PG is an eccentric, stonyasteroid andbinary system, classified asnear-Earth object of theAmor group of asteroids, approximately 900 meters in diameter. Itminor-planet moon has an estimated diameter of 270 meters.
This asteroid was discovered on 3 August 1998, by theLowell Observatory Near-Earth-Object Search (LONEOS) atAnderson Mesa Station, near Flagstaff, Arizona, United States.[2]
1998 PG orbits the Sun at a distance of 1.2–2.8 AU once every 2 years and 10 months (1,046 days). Its orbit has aneccentricity of 0.39 and aninclination of 7° with respect to theecliptic.[1] A firstprecovery was taken atPalomar Observatory in 1978, extending the body'sobservation arc by 20 years prior to its official discovery observation at Anderson Mesa.[2]
The asteroid has anEarthminimum orbital intersection distance of 0.2354 AU (35,200,000 km), which translates into approximately 92lunar distances. It has made multiple close approaches toEarth, with the closest being 35,648,680 kilometers on 15 October 1978.[1] With an aphelion of more than 2.8 AU,1998 PG is also aMars-crosser.
In theSMASS taxonomy,1998 PG is classified as a transitional Sq-type, which is an intermediary between the common stonyS-type and the less frequentQ-type asteroids.[1]
According to the 2006-publishedPhotometric survey of binary near-Earth asteroids byPetr Pravec and derived data from theCollaborative Asteroid Lightcurve Link and the "Johnston's archive",1998 PG measures between 880 and 940 meters in diameter and its surface has analbedo of 0.18 and 0.20, respectively.[4][5][6][a]
In the late 1990s, a rotationallightcurve of1998 PG was obtained from photometric observations by Hungarian astronomersLászló Kiss,Gyula Szabó andKrisztián Sárneczky. Lightcurve analysis gave arotation period of 2.5 hours with a brightness variation of 0.1magnitude (U=n.a.).[7]
A second lightcurve obtained and published in 2000, by an international collaboration of astronomers gave a rotation period of2.51620±0.00003 hours with a brightness amplitude of 0.11 magnitude (U=2).[3]
During the second photometric observation, it was discovered that1998 PG is a probable/possible asynchronousbinary system with aminor-planet moon orbiting it every 7.0035 hours,[6] or twice this period solution.[4]
The moon remains undesignated.[1] The system has an estimated secondary-to-primary mean-diameter ratio of more than 0.3,[3][a] which translates into a diameter of 270 meter for the satellite.[4] The "Johnston's archive" also estimates that the moon's orbit has asemi-major axis of 1.4 kilometers.[4]
From the surface of1998 PG, the moon would have an angular diameter of about 16.3°.[b] For comparison, theSun appears to be 0.5° from Earth.
Thisminor planet wasnumbered by theMinor Planet Center on 30 November 2001.[9] As of 2018, it has not beennamed.[2]
