2011 JY31
A tight binary cold classical Kuiper belt object.
2011 JY31 is a binary object in the Kuiper belt, a cold classical member of that distant region. Astronomers first spotted it on 4 May 2011 using one of the Magellan Telescopes in Chile, as part of a search for potential flyby targets for the New Horizons mission. The binary nature of 2011 JY31 became clear from distant observations by New Horizons in September 2018, which revealed two components of roughly equal size, each about 68 km across, orbiting each other just 200 km apart. The system has not yet been numbered or named by the Minor Planet Center. High-resolution data from New Horizons allowed scientists to estimate the binary orbit and system mass. Assuming a circular orbit, the orbital period is about 46.62 hours, the semimajor axis is roughly 198.6 km, and the total system mass is around 1.7×10¹⁷ kg. The components appear to be similar in size, with a diameter of about 68 km if their density is 0.5 g/cm³. This discovery strengthens the idea that streaming instability is the main process behind the formation of tight and contact binary planetesimals like 486958 Arrokoth, which seem common among cold classical Kuiper belt objects.
Quick Facts
- Minorplanet
- yes
- Background
- #C2E0FF
- Discoverer
- New Horizons KBO Search
- Discovery Site
- Las Campanas Obs.
- Discovered
- 4 May 2011
- Mpc Name
- 2011 JY · 31
- Mp Category
- TNOcubewano / distantbinary
- Epoch
- 1 July 2021 (JD 2459396.5)
- Uncertainty
- 4
- Observation Arc
- 7.4 yr
- Earliest Precovery Date
- 28 April 2011
- Aphelion
- 47.183 AU
Facts from the source article.
Lore & Background
2011 JY31 was discovered on 4 May 2011 by a team of astronomers using one of the Magellan Telescopes in Chile during the New Horizons KBO Search, a survey for a potential flyby target for the New Horizons spacecraft. Its binary nature was not known until distant observations by New Horizons in September 2018 revealed two 68 km-wide components in a tight, mutual orbit 200 km apart.
High-resolution observation by New Horizons made it possible to estimate the binary orbit parameters and system mass. Assuming a circular orbit, the period is 46.62±0.06 hours, the semimajor axis is 198.6±2.9 km, and the system mass is about 1.7×10^17 kg. The components are approximately equal in size, each about 68 km, assuming a density of 0.5 kg/cm³. The minor planet has not been numbered by the Minor Planet Center and remains unnamed.
Reader's Guide
The discovery of 2011 JY31 as a tight binary system adds support to streaming instability as the dominant mechanism in the formation of tight and contact binary planetesimals such as 486958 Arrokoth, which appear to be prevalent in the cold classical Kuiper belt population. Its observation by New Horizons, originally tasked with finding a flyby target, provided high-resolution data that allowed estimation of the binary orbit and system mass. The system's tight orbit and equal-sized components make it a key example of the kind of binary planetesimals thought to have formed directly from gravitational collapse in the early solar nebula. Along with 2014 OS393, another tight binary KBO observed by New Horizons, 2011 JY31 helps constrain models of planetesimal formation in the outer Solar System.
Did You Know?
- Its binary nature was revealed by distant observations by the New Horizons spacecraft in September 2018.
- The two components are each about 68 km wide and orbit 200 km apart.
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