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Hiʻiaka (moon): Difference between revisions

Revision as of 18:47, 18 September 2008

Hiʻiaka

An artist's impresion of Haumea and its moons Namaka and Hiʻiaka.
Discovery
Discovered by	Michael E. Brown, Chad Trujillo, David Rabinowitz, et al.
Discovery date	2005 January 26
Designations
Alternative names	Haumea I
Adjectives	Hiʻiakan
Orbital characteristics[1]
Semi-major axis	49 500 ± 400 km
Eccentricity	0.050 ± 0.003
Orbital period (sidereal)	49.12 ± 0.03 days
Inclination	234.8 ±0.3°
Satellite of	Haumea
Physical characteristics
Mean radius	~155 km
Mass	~4×1020 kg
Mean density	(unknown; close to 1 if water ice)
Synodic rotation period	(unknown)
Axial tilt	(unknown)
Albedo	(unknown)
Temperature	32±3 K
Apparent magnitude	3.3 difference from primary's 17.3

Hiʻiaka (Template:Pron-en, Hawaiian Error using {{IPA symbol}}:『ˈhiʔiˈjakə』not found in list), or Haumea I, is the larger, outer moon of the dwarf planet Haumea. Its provisional designation was S/2005 (2003 EL₆₁) 1.

Discovery and Naming

Hiʻiaka was the first satellite discovered around Haumea. It is named after one of the daughters, Hiʻiaka, of Haumea, though at first it went by the nickname "Rudolph" by its discovery team. It orbits once every 49.12 ±0.03 days at a distance of 49,500 ±400 km, with an eccentricity of 0.050 ±0.003 and an inclination of 234.8 ±0.3° [1]. Mutual occultations occurred in 1999 and will not occur again until 2138.

Size and Brightness

Measured brightness is 5.9 ±0.5% translating into the diameter about 22% of its primary, or in the range of 350 km, assuming similar albedo. To put this in perspective, this moon would be the fifth largest asteroid after 1 Ceres, 2 Pallas, 4 Vesta, and 10 Hygiea if it were in the asteroid belt.

Mass

Only the total mass of the system is known, but assuming the moon has the same density and albedo as the primary, their magnitude difference (3.3) can be used to estimate the mass of the satellite as 1% of the mass of Haumea.

References

External links

• Brown's publication describing the discovery of Hiʻiaka
• Paper describing the composition of Hiʻiaka