Monday, May 23, 2016

A Red and Rough Kuiper Belt Object

1994 JR1 is a Kuiper Belt Object in a 3:2 orbital resonance with Neptune. That means for every three times Neptune goes around the Sun, 1994 JR1 will go around the Sun twice. 1994 JR1 was observed by the Long Range Reconnaissance Imager (LORRI) on NASA's New Horizons spacecraft on 2 November 2015 and on 7 April 2016. This represents the first close observations of a small KBO. Due to Earth's proximity to the Sun, only the dayside of 1994 JR1 is observable from Earth. As a result, the New Horizons spacecraft, which is beyond the orbit of Pluto, is the only means of observing 1994 JR1 at large solar phase angles.

Combining observations from the New Horizons spacecraft with observations from the Hubble Space Telescope and ground based observatories, 1994 JR1 appears to be a very red KBO with a high surface roughness (i.e. it is probably heavily cratered). 1994 JR1 has a relatively fast rotation period of 5.47 ± 0.33 hours and its diameter is assumed to be ~250 km. Simulations also indicate that the orbit of 1994 JR1 brings it close to Pluto every 2.4 million years. Each close encounter causes the orbit of 1994 JR1 to be gravitationally perturbed by Pluto.

Porter et al. (2016), "Red, Rough, Fast, and Perturbed: New Horizons Observations of KBO (15810) 1994 JR1 from the Kuiper Belt", arXiv:1605.05376 [astro-ph.EP]