(419624) 2010 SO₁₆ is a sub-kilometer asteroid in a co-orbital configuration with Earth, classified as near-Earth object and potentially hazardous asteroid of the Apollo group. It was discovered by the Wide-field Infrared Survey Explorer space telescope (WISE) on 17 September 2010.^[1][2]

The orbit was described by Apostolos Christou and David Asher at the Armagh Observatory in Northern Ireland.^[5] The object has an absolute magnitude of 20.5.^[1] Observations by the discovering WISE telescope give a diameter of 357 meters and an albedo of 0.084.^[3][4]

2010 SO₁₆ has a horseshoe orbit that allows it to stably share Earth's orbital neighborhood without colliding with it. It is one of a handful of known asteroids with an Earth-following orbit, a group that includes 3753 Cruithne, and the only known asteroid in an horseshoe orbit with Earth. It is, however, neither an Aten asteroid nor an Apollo asteroid because the semi-major axis of its orbit is neither less than nor greater than 1 AU, but oscillates between approximately 0.996 and 1.004 AU, with a period of about 350 years.^[5] In its ~350 yr horseshoe cycle, it never approaches Earth more closely than about 0.15 AU, alternately trailing and leading.

According to various simulations 2010 SO₁₆ will remain in this orbit for at least 120,000 years and possibly for more than a million years, which is unusually stable compared to other similar objects.^[6] One reason for this stability is its low orbital eccentricity, ${\displaystyle <0.084}$.^[5]

A precovery of 2010 SO₁₆ may have been located in a 2005 Spitzer Space Telescope image.^[7]

• 3753 Cruithne – a horseshoe companion of the Earth
• 2006 RH120 – a small asteroid that sometimes temporarily gets caught in Earth orbit
• 2002 AA29 – a horseshoe companion of the Earth
• Natural satellite
• 2001 GO2
• 2002 AA29
• 2003 YN107
• 2006 JY26
• 2012 FC71
• Orbital resonance