2014 OS393
A binary KBO once considered for New Horizons flyby.
2014 OS393, referred to as PT2 in New Horizons mission press materials, is a trans-Neptunian object in the classical Kuiper belt, the Solar System's outermost region. It was initially detected on July 30, 2014, during the New Horizons KBO Search using the Hubble Space Telescope. Prior to the selection of 486958 Arrokoth in 2015, it was considered a potential flyby target for the New Horizons spacecraft. The object is estimated to be about 42 kilometers (26 miles) in diameter, but its orbit was poorly constrained because observations spanned only a few months. On March 6, 2024, the Minor Planet Center released MPEC 2024-E99, which incorporated additional observations from the New Horizons KBO Search-Subaru program, enabling a reasonably reliable orbital calculation. The discovery was made by the New Horizons Search Team using the Hubble Space Telescope, as the object's magnitude of 26.3 makes it too faint for ground-based telescopes. Preliminary HST searches for Kuiper belt flyby targets began in June 2014, with more intensive observations in July and August. First spotted on July 30, 2014, it was initially labeled e31007AI and nicknamed e3. NASA revealed its existence as a potential New Horizons target in October 2014, designating it PT2. The official name 2014 OS393 was assigned by the Minor Planet Center in March 2015, after better orbital data became available. Orbitally, 2014 OS393 is a trans-Neptunian object, likely a non-resonant classical Kuiper belt object, or cubewano. It orbits the Sun at distances of 43.3 to 44.84 AU, completing one revolution every 292 years (semi-major axis 44.04 AU). Its orbit has an eccentricity of 0.018 and an inclination of 3.8° relative to the ecliptic. Because the object has not been observed since July 2017, its orbit remains fairly uncertain, with an uncertainty parameter of 7. The observation arc begins with a precovery image taken on June 25, 2014, by the New Horizons KBO Search team using the Subaru Telescope at Mauna Kea Observatory in Hawaii, and ends on July 21, 2017, spanning 1122 days. After the New Horizons probe completed its flyby of Arrokoth, it began observing other nearby Kuiper belt objects, including 2014 OS393. Observations of brightness variations at high phase angles allowed the New Horizons probe to make a rough determination of its rotation period as well as its shape.
Quick Facts
- Minorplanet
- yes
- Background
- #C2E0FF
- Discoverer
- New Horizons KBO Search
- Discovery Site
- Hubble Space Telescope
- Discovered
- 30 July 2014
- Mpc Name
- 2014 OS · 393
- Mp Category
- TNOcubewano / distantbinary
- Epoch
- 9 June 2026 (JD 2461200.5)
- Uncertainty
- 7
- Observation Arc
- 3.07 y (1122 d)
- Aphelion
- 44.6277 AU
- Perihelion
- 43.1635 AU
Facts from the source article.
Lore & Background
2014 OS393 was discovered by the New Horizons Search Team using the Hubble Space Telescope, as its magnitude of 26.3 is too faint for ground-based telescopes. Preliminary observations began in June 2014, and the object was first seen on July 30, 2014, initially designated e31007AI and nicknamed e3. Its existence as a potential New Horizons target was revealed by NASA in October 2014, designated PT2, and the official name 2014 OS393 was assigned by the Minor Planet Center in March 2015 after better orbit information became available. The object orbits the Sun at 43.3–44.84 AU every 292 years, with an eccentricity of 0.018 and inclination of 3.8°. Its orbit remains poorly determined due to a short observation arc ending in July 2017. Observations by New Horizons at high phase angles showed large brightness variations, suggesting either an elongated shape or a binary system. In 2021, Hal Weaver confirmed it is a binary with two components about 30 km in diameter, separated by about 150 km. After the Pluto flyby, New Horizons considered several KBO targets for its next encounter. On 28 August 2015, the team selected 2014 MU69 (Arrokoth), eliminating 2014 OS393 and others. The spacecraft passed 2014 OS393 in January 2019 at a distance of less than 0.1 AU, making it the second closest KBO observed by New Horizons after Arrokoth.
Reader's Guide
2014 OS393 is notable as a binary trans-Neptunian object in the classical Kuiper belt, first observed by the Hubble Space Telescope in 2014 as part of the search for New Horizons flyby targets. Though it was not selected for the primary flyby—Arrokoth was chosen in August 2015—the object was later observed by New Horizons during its extended mission. The spacecraft passed within 0.1 AU in January 2019, making it the second closest KBO observed by the probe. Its binary nature was confirmed in 2021 by Hal Weaver, with two components roughly 30 km in diameter separated by about 150 km. The object's orbit remains poorly determined due to a limited observation arc, and it has not been numbered or named by the Minor Planet Center. Its legacy lies in its role as a secondary target for New Horizons and as a rare example of a resolved binary KBO observed at close range.
Did You Know?
- 2014 OS393 was first observed on 30 July 2014 by the Hubble Space Telescope.
- It was a potential flyby target for New Horizons until Arrokoth was selected in August 2015.
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