Its minor-planet moon, provisionally designated S/2001 (66063) 1, was discovered in September 2003. It has an orbital period of 14.53 hours and measures approximately 48% of its primary, or 380 meters.[1][3] It is one of seven known Aten binaries as of 2017.
Interaction with Earth
1998 RO1's orbit is very eccentric, with an aphelion beyond the orbit of Mars and a perihelion inside the orbit of Mercury.[3] It has an orbital period of 360.29 days (0.99 years) and makes close approaches to Earth.[1] But 1998 RO1 makes closer approaches to other inner planets, especially Mars. Its closest approach to a planet between 1950–2200 was to Mars, as it passed 0.00898 AU (1,343,000 km) from Mars on 18 March 1964, and will pass 0.0054 AU (810,000 km) from Mars on 12 October 2065.[1]
Moon
1998 RO1 has one moon, S/2001 (66063) 1. This moon was discovered from lightcurve observations going from 13 to 28 September 2013, and was confirmed by radar observations from the Arecibo Observatory one year later. It is in a very close orbit to 1998 RO1, with a semi-major axis of 800 m (2,600 ft) and an eccentricity of 0.06,[3] giving it a periapsis of 752 m (2,467 ft) and an apoapsis of 848 m (2,782 ft). S/2001 (66063) 1 takes 14.54 hours to complete one orbit around 1998 RO1.[3]
From the surface of 1998 RO1, S/2001 (66063) 1 would have an apparent diameter of roughly 41°.[a] For comparison, the Sun appears to be 0.5° from Earth. The secondary orbits its primary in a manner very similar to the adjunct image, where the red cross is the center of mass.
^Abell, P. A.; Gaffey, M. J.; Landis, R. R.; Jarvis, K. S. (March 2005). "Compositional Investigation of Binary Near-Earth Asteroid 66063 (1998 RO1): A Potentially Undifferentiated Assemblage". 36th Annual Lunar and Planetary Science Conference: 2283. Bibcode:2005LPI....36.2283A.
^Pravec, Petr; Harris, Alan W.; Kusnirák, Peter; Galád, Adrián; Hornoch, Kamil (September 2012). "Absolute magnitudes of asteroids and a revision of asteroid albedo estimates from WISE thermal observations". Icarus. 221 (1): 365–387. Bibcode:2012Icar..221..365P. doi:10.1016/j.icarus.2012.07.026.