405 Thia is a very large main-belt asteroid. It is classified as a C-type asteroid and is probably composed of carbonaceous material. This object was discovered by Auguste Charlois on July 23, 1895, in Nice, and was named after Theia (sometimes written Thea or Thia), a Titaness in Greek mythology.

In 2002, the asteroid was detected by radar from the Arecibo Observatory at a distance of 1.31 AU. The resulting data yielded an effective diameter of 125 ± 16 km. NEOWISE data suggests the asteroid is 110 km in diameter.

On 4 May 1990 Thia passed 0.969 AU (145.0 million km; 377 LD) from Earth and will pass that close again on 29 April 2073.

405 Thia currently has a Minimum orbit intersection distance with Earth of 0.976 AU (146.0 million km; 380 LD). On 2 June 2023 the asteroid reached perihelion (closest approach to the Sun).

Thia Earth approach on 2023-Mar-20
Date & time of closest approachEarth distance (AU)Sun distance (AU)Velocity wrt Earth (km/s)Velocity wrt Sun (km/s)Uncertainty region (3-sigma)Reference
2023-03-20 19:401.057 AU (158.1 million km; 411 LD)2.006 AU (300.1 million km; 781 LD)6.823.3± 16 km

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