provisional designation
Provisional designation in astronomy is the naming convention applied to astronomical objects immediately following their discovery. The provisional designation is usually superseded by a permanent designation once a reliable orbit has been calcu ...
) 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 axe ...
(cubewano) and
binary system
A binary system is a system of two astronomical bodies of the same kind that are comparable in size. Definitions vary, but typically require the center of mass to be located outside of either object. (See animated examples.)
The most common ki ...
made up of components of almost equal size, called Sila and Nunam, orbiting beyond
Neptune
Neptune is the eighth and farthest known planet from the Sun. It is the List of Solar System objects by size, fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 t ...
in the
Solar System
The Solar SystemCapitalization 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 "Sola ...
. 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 (; 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 E. Brown, Michael Brown) for 2012 "for discovering and characterizing the K ...
,
David C. Jewitt
David Clifford Jewitt (born 1958) is a British-American astronomer who studies the Solar System, especially its minor bodies. He is based at the University of California, Los Angeles, where he is a Member of the Institute for Geophysics and Pla ...
,
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 ...
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 Hawaiʻi, United States. The facilities are located in a 525-acre (21 ...
, Hawaii, and given the provisional designation . It was resolved as a binary system in Hubble observations of 22 October 2002 by
Denise C. Stephens
Denise may refer to:
* Denise (given name), people with the given name ''Denise''
* Denise (computer chip), a video graphics chip from the Amiga computer
* "Denise" (song), a 1963 song by Randy & the Rainbows
* Denise, Mato Grosso, a municipalit ...
Inuit deities
Inuit religion is the shared spiritual beliefs and practices of the Inuit, an Indigenous peoples of the Americas, indigenous people from Alaska, northern Canada, Greenland, and parts of Siberia. Their religion shares many similarities with some A ...
.
Sila
Sila may refer to :
Places
* Sila Region, Chad
** Sila Department, Chad, part of Sila Region
* La Sila, a mountainous area of Calabria, Italy
** Sila National Park
* Sila, Numidia, a former ancient city and bishopric, now Bordj-El-Ksar in Alge ...
Inuktitut
Inuktitut ( ; , Inuktitut syllabics, syllabics ), also known as Eastern Canadian Inuktitut, is one of the principal Inuit languages of Canada. It is spoken in all areas north of the North American tree line, including parts of the provinces of ...
''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 axe ...
). 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 relation ...
with
Neptune
Neptune is the eighth and farthest known planet from the Sun. It is the List of Solar System objects by size, fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 t ...
.
Physical characteristics
In 2010, thermal flux from Sila–Nunam in the
far-infrared
Far infrared (FIR) or long wave refers to a specific range within the infrared spectrum of electromagnetic radiation. It encompasses radiation with wavelengths ranging from 15 μm ( micrometers) to 1 mm, which corresponds to a freque ...
was measured by the
Herschel Space Telescope
The Herschel Space Observatory was a space observatory built and operated by the European Space Agency (ESA). It was active from 2009 to 2013, and was the largest infrared telescope ever launched until the launch of the James Webb Space Telesco ...
. As a result, its size, while it was assumed to be a single body, was estimated to lie within the range of . 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 that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those of ...
. There are no water ice absorption bands in its near-infrared spectrum, which resembles that of
Ixion
In Greek mythology, Ixion ( ; ) was king of the Lapiths, the most ancient tribe of Thessaly.
Family
Ixion was the son of Ares, or Leonteus (mythology), Leonteus, or Antion and Perimele, or the notorious evildoer Phlegyas, whose name connotes " ...
.
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 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 .