79360 Sila–Nunam

Template: Infobox Asteroid / Maintenance / Error 2

( 79360 ) Sila is a transneptunisches object in the Kuiper Belt, which is classified as Cubewano. As Sila has an almost equally large companion called Nunam, this system is referred to as a double asteroid system ( 79360 ) Sila Nunam.

• 3.1 size
• 3.2 Internal structure
• 3.3 Surface

Discovery and designation

Sila was discovered on February 3, 1997 by a team of astronomers from the California Institute of Technology in Pasadena consisting of Jane X. Luu, David C. Jewitt, Chadwick A. Trujillo and Jun Chen at the Mauna Kea Observatory in Hawaii. The asteroid first received the provisional designation 1997 CS29.

On January 9, 2012 Sila received along with Nunam the official name, named after the Inuit gods. Sila ( "spirit ") is the Inuit god of sky, weather and vitality. Nunam is the earth goddess, in some traditions as Silas woman. Nunam created the land animals and, in some traditions, the Inuit people. In other traditions, it was Sila, who created the first humans out of wet sand. Sila breathed an Inuit life.

Web properties

Orbit

Sila orbits the sun on a prograde, slightly elliptical orbit between 6.500168 billion km ( 43.450 AU) and 6.665842 billion km ( 44.558 AU) distance from its center. The orbital eccentricity is 0.013, the orbit is inclined 2.243 ° to the ecliptic.

The orbital period of Sila is 291.91 years or 106,621.9376946928 days, 22 hours, 30 minutes and 17 seconds. Overall, these orbital elements similar to those of Quaoar ( 285.9 years orbital period ).

Near- orbital resonance

Sila moves close to a 7:4 resonance with Neptune. Therefore, the asteroid is classified as Cubewano and not as resonant KBO. An object of the 7:4 resonance is 1999, for example CD158.

Physical Properties

Size

The diameter of Sila amounts to 248 km, where his companion Nunam is smaller by only 5% at 236 km. Measurements in the far infrared region by the Herschel space telescope you first went from a diameter of 250 to 420 km from, but for a single body.

Internal construction

The extremely low system density of 0.72 g / cm ³, which is far below that of water, indicates that water ice on both bodies would be dominant, which as an explanation of the low density, however, is not sufficient, since even pure ice with 0.91 g / cm ³ is even closer. Thus, it can be assumed that both the body inside must have cavities. (→ Rubble Piles )

Surface

In visible light Sila and Nunam are very red and have a flat spectrum with no features in the near infrared, which shows no water ice absorptions, which is similar to the spectrum of Ixion. It appears that the surfaces of both components have been renewed by ejecta from Impakten on each other's body. The surface temperature should be about -231 ° C ( 42 K).

Moon

On October 22, discovered in 2002 another team of astronomers at Keith S. Noll with the Hubble Space Telescope that Sila has a natural companion of almost the same size. Thus, this system in the relative sizes of strong similarity to the L5- Jupiter - Trojan system Patroclus - Menoetius, whose components, however, have about half the diameter.

Research

After his discovery could be Sila ( and Nunam ) dating back to photos up to 1997 and therefore the orbit of the system is now relatively well understood. Overall, the asteroid was observed by different telescopes such as the Hubble Space Telescope and ground-based telescopes also, so far a total of 219 times in 15 years. (As of Sept. 2012 )