2011 KW48
A small Kuiper belt object observed by New Horizons in 2015.
2011 KW48 is a minor planet in the inner classical region of the Kuiper belt, the distant zone of icy bodies beyond Neptune. Its diameter is estimated at roughly 77 kilometers. Astronomers first spotted it on 29 May 2011 using the Subaru Telescope at Hawaii’s Mauna Kea Observatory as part of the New Horizons KBO Search. The New Horizons spacecraft later observed the object from a distance in January 2015.
The object takes about 230 years to complete one orbit around the Sun, ranging from 32.4 to 42.7 AU. Its orbit has an eccentricity of 0.14 and an inclination of 3.6 degrees to the ecliptic. Because it was tracked only 12 times over 33.8 days in 2011, its current orbit is highly uncertain.
During a 10-day span in January 2015, New Horizons—then calling the object VNH0004—observed it from roughly 0.5 AU away. At that range, the probe could not resolve surface details or analyze its composition, but it did search for moons and measure the object’s phase curve.
Based on an absolute magnitude of 8.8 and an assumed albedo of 0.09, the estimated diameter is 77 kilometers. As of 2018, no rotational lightcurve had been obtained, so the rotation period, pole, and shape remain unknown. As of 2025, this minor planet has not been assigned a number or a name.
Quick Facts
- Minorplanet
- yes
- Background
- #C2E0FF
- Discoverer
- New Horizons KBO Search 266
- Discovery Site
- Subaru Telescope
- Discovered
- 29 May 2011 / (discovery: first observed only)
- Mpc Name
- 2011 KW · 48
- Mp Category
- TNOinner classic / distant
- Epoch
- 8 June 2011 (JD 2455720.5)
- Uncertainty
- n.a.
- Observation Arc
- 34 days
- Aphelion
- 42.676 AU
- Perihelion
- 32.368 AU
Facts from the source article.
Lore & Background
2011 KW48 was first observed on 29 May 2011 during the New Horizons KBO Search (266) by astronomers using the Subaru Telescope at the Mauna Kea Observatory on Hawaii. It was observed 12 times by the Mauna Kea and Las Campanas observatories over about 33.8 days, resulting in an extremely uncertain orbit. The object orbits the Sun at a distance of 32.4–42.7 AU once every 229 years and 10 months, with an eccentricity of 0.14 and an inclination of 3.6°.
Between 4–15 January 2015, the New Horizons spacecraft actively observed this object—then temporarily designated VNH0004—at a distance of about 0.5 AU. This was too far to resolve surface features or perform spectroscopic analyses, but the spacecraft was able to search for possible satellites and observe its phase curve. Based on an absolute magnitude of 8.8 and an assumed albedo of 0.09, Johnston's Archive estimates a mean diameter of approximately 77 kilometers. As of 2018, no rotational lightcurve had been obtained, so its rotation period, pole, and shape remain unknown.
As of 2025, this minor planet has not been numbered or named.
Reader's Guide
2011 KW48 holds significance primarily as a target of opportunity for the New Horizons mission. Although the spacecraft's distant flyby in January 2015 could not resolve surface features or perform compositional spectroscopy, it provided valuable data on the object's phase curve and allowed a search for satellites. This observation contributed to the broader understanding of small Kuiper belt objects, particularly those in the inner classical region. The object's extremely uncertain orbit, due to only 12 observations over 33.8 days, underscores the challenges of characterizing distant trans-Neptunian objects. Its legacy is tied to the New Horizons mission's extended exploration of the Kuiper belt, demonstrating the capability to observe even small, unnumbered objects from a spacecraft. The lack of a rotational lightcurve and unknown physical properties highlight the need for further observations.
Did You Know?
- The New Horizons spacecraft observed it from a distance of about 0.5 AU in January 2015.
- Its orbit is extremely uncertain due to only 12 observations over 33.8 days.
More in Trans-Neptunian Objects, Part 3 1-24
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