2020 SO

As it approached Earth the trajectory indicated the geocentric orbital eccentricity was less than 1 by 15 October 2020,[10][lower-alpha 1] and the object became temporarily captured on 8 November when it entered Earth's Hill sphere.[11] It entered via the outer Lagrange point L₂ and will exit via Lagrange point L₁. During its geocentric orbit around Earth, 2020 SO made a close approach to Earth on 1 December 2020 at a perigee distance of approximately 0.13 lunar distances (50,000 km; 31,000 mi).[4] It will also make another close approach on 2 February 2021, at a perigee distance of approximately 0.58 LD (220,000 km; 140,000 mi).[4] Since discovery the time of uncertainty for the February 2021 closest approach to Earth has been reduced from ±3 days to less than 1 minute.[4] It will leave Earth's Hill sphere around 8 March 2021.[12][lower-alpha 1]

The Surveyor 2 Centaur rocket booster

Paul Chodas of the Jet Propulsion Laboratory suspects 2020 SO of being the Surveyor 2 Centaur rocket booster, launched on 20 September 1966.[11][12][13] The Earth-like orbit and low relative velocity suggest a possible artificial object. Spectroscopy may help determine if it is covered in white titanium dioxide paint.[14] Goldstone radar will make bistatic observations transmitting from the 70-meter DSS-14 and receiving at the 34-meter DSS-13.[15] As a result of the bistatic DSS-14/RT-32 radar observations, a rotation period of about 9.5 seconds was obtained,[16] which corresponds to the photometric observations.[6] Obtained range-Doppler radar images[16] confirm that the object has an elongated shape with a length of about 10 meters and a width of about 3 meters.

Around the time of closest approach on 1 December 2020, the object was only brighten to about apparent magnitude 14.1,[8] and required a telescope with roughly a 150mm (6") objective lens to be seen visually.[17] It displays a large light curve amplitude of 2.5 magnitudes, signifying a highly elongated shape or albedo variations on its surface. It has a rotation period of approximately 9 seconds.[18]

At the time of its discovery, 2020 SO had unremarkable motion typical of a main-belt asteroid. However, the four observations that Pan-STARRS obtained over the course of 1.4 hours showed non-linear motion due to the rotation of the observer around Earth's axis, which is a signature of a nearby object.[1][10]

Animation of 2020 SO's orbit

Around the Sun

Around the Earth

  Sun ·    Earth ·    2020 SO ·    Moon

In January and February of 2036, it will again approach Earth with a geocentric eccentricity less than 1 since the relative velocities will be small,[10] but will not be within Earth's Hill sphere of 0.01 AU (1.5 million km).[4][lower-alpha 3]

• J002E3
• 2018 AV2, a similar "asteroid" discovered in 2018 in a temporary orbit around Earth, now no longer considered to be an asteroid, but suspected to be the Snoopy module from Apollo 10
• Temporary satellite

• Earth May Have Recaptured a 1960s-Era Rocket Booster, Tony Greicius, NASA, 12 November 2020
• Animation of the Line of Variation (via clone orbits) stretching out from December 2020 to May 2021
• "Pseudo-MPEC" for P116rK2, Project Pluto, 19 September 2020
• 21 Nov 2020 image – Osservatorio Sormano / E. Colzani
• 01 Dec 2020 image and rotation – Virtual Telescope Project / G. Masi
• 01 Dec 2020 time-lapse and photometry – Virtual Telescope Project / G. Masi
• 2020 SO at NeoDyS-2, Near Earth Objects—Dynamic Site
  • Ephemeris · Obs prediction · Orbital info · MOID · Proper elements · Obs info · Close · Physical info · NEOCC
• 2020 SO at ESA–space situational awareness
  • Ephemerides · Observations · Orbit · Physical Properties · Summary
• 2020 SO at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters