79360 Sila–Nunam, provisional designation , is a cold

classical Kuiper belt object A classical Kuiper belt object, also called a cubewano ( "QB1-o"), is a low-eccentricity Kuiper belt object (KBO) that orbits beyond Neptune and is not controlled by an orbital resonance with Neptune. Cubewanos have orbits with semi-major a ...

(cubewano) and

binary system A binary system is a system of two astronomical bodies which are close enough that their gravitational attraction causes them to orbit each other around a barycenter ''(also see animated examples)''. More restrictive definitions require that th ...

made up of components of almost equal size, called Sila and Nunam, orbiting beyond Neptune in the

Solar System The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...

. The name of the system is the combined names of the two bodies, Sila and Nunam.Sila–Nunam Mutual Events
(Lowell)

Discovery

Sila–Nunam was discovered on 4 February 1997 by

Jane X. Luu Jane X. Luu ( vi, ; born July 1963) is a Vietnamese-American astronomer and defense systems engineer. She was awarded the Kavli Prize (shared with David C. Jewitt and Michael Brown) for 2012 "for discovering and characterizing the Kuiper Belt ...

, David C. Jewitt,

Chad Trujillo Chadwick A. Trujillo (born November 22, 1973) is an American astronomer, discoverer of minor planets and the co-discoverer of Eris, the most massive dwarf planet known in the Solar System. Trujillo works with computer software and has examined ...

, and Jun Chen at the

Mauna Kea Observatory The Mauna Kea Observatories (MKO) are a group of independent astronomical research facilities and large telescope observatories that are located at the summit of Mauna Kea on the Big Island of Hawaiʻi, United States. The facilities are locate ...

, Hawaii, and given the provisional designation . 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.

Name

The two components are named after Inuit deities. Sila "air" ( Iñupiaq ''siḷa'' , Inuktitut ''sila'') is the Inuit god of the sky, weather, and life force. Nuna "earth" (Iñupiaq amn Inuktitut ''nuna-m'' ) 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). Sila breathed life into the Inuit.

Orbit

Sila–Nunam is a dynamically cold classical system (

cubewano A classical Kuiper belt object, also called a cubewano ( "QB1-o"), is a low-eccentricity Kuiper belt object (KBO) that orbits beyond Neptune and is not controlled by an orbital resonance with Neptune. Cubewanos have orbits with semi-major a ...

). It orbits very close to 4:7

mean-motion resonance In celestial mechanics, orbital resonance occurs when orbiting bodies exert regular, periodic gravitational influence on each other, usually because their orbital periods are related by a ratio of small integers. Most commonly, this relationsh ...

with Neptune.

Physical characteristics

In 2010, thermal flux from Sila–Nunam in the

far-infrared Far infrared (FIR) is a region in the infrared spectrum of electromagnetic radiation. Far infrared is often defined as any radiation with a wavelength of 15 micrometers (μm) to 1 mm (corresponding to a range of about 20 THz to ...

was measured by the Herschel Space Telescope. As a result, its size, while it was assumed to be a single body, was estimated to lie within the range . Now that it is known to be a binary system, one body 95% the size of the other, the diameters are estimated to be . Sila–Nunam is very red in visible light and has a flat featureless spectrum in the

near-infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...

. There are no water ice absorption bands in its near-infrared spectrum, which resembles that of

Ixion In Greek mythology, Ixion ( ; el, Ἰξίων, ''gen''.: Ἰξίονος means 'strong native') was king of the Lapiths, the most ancient tribe of Thessaly. Family Ixion was the son of Ares, or Leonteus, or Antion and Perimele, or the not ...

. Sila–Nunam experiences periodic changes in brightness with the full period, which is equal to the orbital binary period (see below). The light curve is double peaked with the secondary period equal to the half of the full period. The rotation of both components of the system 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.

Double system

Sila and Nunam are so close in size (within 5%) that they may be thought of as a double cubewano. Sila is approximately 250 km in diameter and Nunam 236 km. Their albedo is about 9%. They orbit at a distance of every 12.51 days: : Each has apparently been resurfaced with ejecta from impacts on the other.Rabinowitz, et al. (2009).
Evidence for Recent Resurfacing of the Binary Kuiper Belt Object 1997 CS29
.

References

External links

* * {{DEFAULTSORT:Sila-Nunam 079360 Discoveries by Chad Trujillo Discoveries by Jun Chen (astronomer) Discoveries by Jane Luu Discoveries by David C. Jewitt Named minor planets Binary trans-Neptunian objects 079360 19970203