(148780) Altjira 1

(148780) Altjira 1
Central body	(148780) Altjira
Properties of the orbit
Major semi-axis	9904 ± 56 km
Periapsis	6492 km
Apoapsis	13,316 km
eccentricity	0.3445 ± 0.0045
Orbit inclination	35.19 ± 0.19 °
Orbital time	139.561 ± 0.047 d
Physical Properties
Albedo	≈ ${\displaystyle 0{,}043_{-0,010}^{+0,182}\mathrm {} }$
Medium diameter	${\displaystyle 221_{-125}^{+34}\mathrm {} }$ km
surface	153,000 km 2
Medium density	≈ g / cm 3 ${\displaystyle 0{,}30_{-0,014}^{+0,50}\mathrm {} }$
discovery
Explorer	? ( Hubble Space Telescope )
Date of discovery	August 6, 2006

(148780) Altjira 1 is the only 10.1% smaller component (" moon ") of the Kuiper belt - asteroids and cubewanos (148780) Altjira . Its estimated mean diameter is 221 kilometers. Therefore this system can also be understood as a double asteroid system.

Discovery and naming

S / 2007 (148780) 1 was discovered on August 6, 2006 by a team of astronomers through examination of images of the system taken with the Hubble Space Telescope on August 26, 2006. The discovery was announced on March 14, 2007; the moon was given the provisional name (148780) Altjira 1 .

Overall, the system has been observed through several earth-based telescopes, a total of 70 times within 7 years. (As of Sept. 2017)

Track properties

S / 2007 (148780) 1 orbits Altjira on a retrograde , very elliptical orbit at an average distance of 9904 km from its center (around 80 Altjira or 90 (148780) Altjira 1 radii). The orbit eccentricity is 0.3, the orbit is inclined 35.2 ° with respect to the ecliptic .

S / 2007 (148780) 1 orbits the common center of mass with Altjira in 139 days, 13 hours and 28 minutes, which corresponds to around 764.2 orbits in an Altjira year (around 292 earth years). The orbit of S / 2007 (148780) 1 is believed to be stable because it is well within Altjira's Hill radius of 550,000 km, but also well outside of the synchronous orbit. A double-bound rotation can therefore be ruled out due to the long orbit of the moon.

Physical Properties

size

According to current data, (148780) Altjira 1 has a diameter of 221 km (89.9% of the central body), based on Altjira's estimated density of 0.3 g / cm ³ and the corresponding assumed equal reflectivity of 4%.

Assuming a mean diameter of 221 km, the surface area is approximately 153,000 km ² , which is slightly less than the area of Nepal .

Determination of the diameter for (148780) Altjira 1

year	Dimensions km	source
2011	147.5	Grundy et al. a.
2012	171.9	Vilenius et al. a.
2014	221.0 + 034.0- 0125.0	Vilenius et al. a.

The most precise / current determination is marked in bold .

internal structure

The unusually low mean density of 0.3 g / cm ³ is an indication that it is not a compact body, but that the object is likely to be a rubble pile , an accumulation of dust and rocks interspersed with cavities .

See also

• List of moons from asteroids
• List of moons of planets and dwarf planets
• List of trans-Neptunian objects
• List of asteroids
• Double asteroid

Web links

• Wm. Robert Johnston: (148780) Altjira (English)

Individual evidence

1. ↑ JPL: (148780) Altjira at JPL. Retrieved September 20, 2017 . 
2. ↑ WM Grundy et al .: Five new and three improved mutual orbits of transneptunian binaries (March 2011) (PDF). Retrieved September 20, 2017 . 
3. ↑ E. Vilenius et al. a .: "TNOs are Cool": A survey of the trans-Neptunian region VI. Herschel / PACS observations and thermal modeling of 19 classical Kuiper belt objects (April 2012). Retrieved January 23, 2019 . 
4. ↑ E. Vilenius et al .: TNOs are Cool: A survey of the trans-Neptunian region - X. Analysis of classical Kuiper belt objects from Herschel and Spitzer observations (March 2014) (PDF). Retrieved September 20, 2017 .