2012 HE85 is a small, resonant trans-Neptunian object from the Kuiper belt, located in the outermost region of the Solar System, approximately 74 kilometers (46 miles) in diameter. It was first observed by a team of astronomers using one of the Magellan Telescopes in Chile during the New Horizons KBO Search on 18 April 2012, in order to find a potential flyby target for the New Horizons spacecraft.[1] The likely 5:9 resonant object was imaged by the spacecraft from afar at a record distance from Earth in 2017.[7]
Trajectory of New Horizons and other nearby Kuiper belt objects
When the New Horizons spacecraft imaged 2012 HE85 in 2017, it was the farthest from Earth ever captured by a spacecraft. The image was taken by the spacecraft's Long Range Reconnaissance Imager (LORRI) on 5 December 2017 at more than 6.12 billion kilometers (40.9 AU) away from Earth. This record was previously held by the Voyager 1 spacecraft which took the iconic Pale Blue Dot image at 6.06 billion kilometers from Earth in February 1990.[7]
In December 2017, New Horizons also imaged the classical Kuiper belt object (516977) 2012 HZ84, which was discovered by the same team of astronomers the night before they first observed 2012 HE85.[7] Both objects held this record for little more than one year, until it was superseded on New Year's Eve 2018/19, when New Horizons made its close flyby on 486958 Arrokoth at a new record distance of 6.4 billion kilometers from Earth.[8]
Physical characteristics
According to Johnston's Archive, the object measures 74 kilometers in diameter based on an assumed albedo of 0.09 and an absolute magnitude of 8.9.[4][5] Another estimates gives a smaller diameter of 31 kilometers due to an assumed albedo of 0.15.[3] As of 2019, no rotational lightcurve of 2012 HE85 has been obtained from photometric observations. The body's rotation period, pole and shape remain unknown.[4]
