79360 Sila–Nunam
A cold classical Kuiper belt binary system of near-equal size.
79360 Sila–Nunam, first spotted on 4 February 1997 from Hawaii’s Mauna Kea Observatory, is a binary system in the cold classical Kuiper belt. Its two nearly equal-sized components, Sila and Nunam, orbit each other beyond Neptune. The system’s name combines theirs.
The discovery team included Jane X. Luu, David C. Jewitt, Chad Trujillo, and Jun Chen; the object received the provisional designation 1997 CS29. Denise C. Stephens and Keith S. Noll resolved it as a binary using the Hubble Space Telescope on 22 October 2002, with the announcement following on 5 October 2005.
Sila and Nunam take their names from Inuit deities. Sila (meaning “air” in Iñupiaq and Inuktitut) is the god of sky, weather, and life force. Nunam (from “nuna,” meaning “earth”) is the Earth goddess, in some traditions Sila’s wife. Nunam created land animals and, in some accounts, the Inuit people; in other traditions, Sila shaped the first people from wet sand and breathed life into them.
Orbitally, Sila–Nunam is a dynamically cold cubewano, moving very close to a 4:7 mean-motion resonance with Neptune.
In 2010, the Herschel Space Telescope measured its far-infrared thermal flux. When still assumed to be a single body, its size was estimated between 250 and 420 km. Now known as a binary, with one component 95% the size of the other, the diameters are roughly 243 km and 230 km. The system appears very red in visible light and shows a flat, featureless near-infrared spectrum, lacking water ice absorption bands and resembling that of Ixion.
Its brightness varies periodically, with a full period equal to the binary orbital period. The light curve is double-peaked, so the secondary period is half the full period. Both components rotate synchronously with their orbit, are elongated, and keep their long axes pointed toward each other. Mutual occultation events occurred between 2009 and 2017.
Because Sila and Nunam differ in size by only about 5%, they are often considered a double cubewano. Sila is roughly 250 km across, Nunam about 236 km. Their albedo is around 9%. They orbit each other at a distance of 2,777 ± 19 km every 12.51 days. Each body appears to have been resurfaced by ejecta from impacts on the other.
Quick Facts
- Minorplanet
- yes
- Background
- #C2E0FF
- Pronounced
- ' · s · iː · l · ə · _ · ' · n · uː · n · ə · m
- Adjectives
- Silaupian, Nunaupian
- Discoverer
- J. X. Luu / D. C. Jewitt / C. A. Trujillo / J. Chen
- Discovery Site
- Mauna Kea Obs.
- Discovered
- 4 February 1997
- Mpc Name
- (79360) Sila–Nunam
- Mp Category
- TNO (cubewano)
- Epoch
- 13 January 2016 (JD 2457400.5)
- Semimajor
- 44.1157 AU
- Perihelion
- 43.3862 AU
Facts from the source article.
Lore & Background
Sila–Nunam was discovered on 4 February 1997 by Jane X. Luu, David C. Jewitt, Chad Trujillo, and Jun Chen at the Mauna Kea Observatory, Hawaii, and given the provisional designation 1997 CS29. It was resolved as a binary system in Hubble observations of 22 October 2002 by Denise C. Stephens and Keith S. Noll and announced on 5 October 2005.
The two components are named after Inuit deities. Sila is the Inuit god of the sky, weather, and life force. Nuna is the Earth goddess, in some traditions Sila's wife. Nuna created the land animals and, in some traditions, the Inuit; in other traditions Sila created the first people out of wet sand and breathed life into them.
Sila–Nunam is a dynamically cold classical system orbiting very close to 4:7 mean-motion resonance with Neptune. In 2010, thermal flux from the system was measured by the Herschel Space Telescope, leading to size estimates. The system is very red in visible light and has a flat featureless spectrum in the near-infrared, with no water ice absorption bands, resembling that of Ixion. The rotation of both components is synchronously locked with the orbital motion, and both bodies are elongated with their long axes pointing to each other. From 2009 to 2017 Sila–Nunam experienced mutual occultation events.
Reader's Guide
Sila–Nunam is significant as a cold classical Kuiper belt object and a binary system with components of almost equal size, making it a rare example of a double cubewano. Its discovery and resolution as a binary system contributed to understanding the dynamics and composition of trans-Neptunian objects. The system's orbit near the 4:7 mean-motion resonance with Neptune provides insight into the structure of the Kuiper belt. The mutual occultation events from 2009 to 2017 allowed detailed study of the components' shapes and synchronous rotation. The lack of water ice absorption bands and its red color, similar to Ixion, suggest a surface composition distinct from other Kuiper belt objects. The naming after Inuit deities reflects cultural connections in astronomical nomenclature. The system's legacy lies in its role as a benchmark for binary formation and evolution in the outer Solar System.
Did You Know?
- Sila–Nunam was discovered on 4 February 1997 at the Mauna Kea Observatory.
- The two components are named after Inuit deities: Sila (sky, weather, life force) and Nuna (Earth goddess).
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