Margaret (moon)
From Wikipedia, the free encyclopedia
| Discovery | |||||||
|---|---|---|---|---|---|---|---|
| Discovered by | Scott S. Sheppard, and David C. Jewitt |
||||||
| Discovered in | August 29, 2003 | ||||||
| Orbital characteristics | |||||||
| Mean radius | 14,345,000 km | ||||||
| Eccentricity | 0.6608[1] (mean) | ||||||
| Orbital period | 1687.01 d | ||||||
| Inclination | 57° (to the ecliptic)[2] | ||||||
| Is a satellite of | Uranus | ||||||
| Physical characteristics | |||||||
| Mean diameter | ~20 km (estimate)[2] | ||||||
| Surface area | ~1300 km2 (estimate) | ||||||
| Volume | ~4200 km3 (estimate) | ||||||
| Mass | ~5.4×1015 kg (estimate) | ||||||
| Mean density | ~1.3 g/cm3 (assumed) | ||||||
| Surface gravity | ~0.0023 m/s2 (estimate) | ||||||
| Escape velocity | ~0.0085 km/s (estimate) | ||||||
| Rotation period | ? | ||||||
| Axial tilt | ?° | ||||||
| Albedo | 0.04 (assumed)[2] | ||||||
| Surface temp. |
|
||||||
| Atmospheric pressure | 0 kPa | ||||||
Margaret (mar'-grət, IPA: /ˈmɑrgrɨt/) is the only prograde irregular satellite of Uranus. It was discovered by Scott S. Sheppard, et al. in 2003 and given the provisional designation S/2003 U 3.[3]
Confirmed as Uranus XXIII, it was named after the servant of Hero in William Shakespeare's play Much Ado About Nothing[4]
Contents |
[edit] Orbit
Margaret stands out as the only prograde irregular satellite of Uranus. The diagram illustrates the orbital parameters of Margaret, unique among the irregular satellites of Uranus, with inclination on the vertical axis and the eccentricity of the orbits represented by the segments extending from the pericentre to the apocentre.
Margaret's inclination of 57° is close to the limit of stability. The intermediate inclinations 60 < i < 140 are devoid of known moons due to the Kozai instability.[2] In this instability region, solar perturbations at apoapse cause the moons in this region to acquire large eccentricities that lead to collisions or ejection over 10 million to a billion years. Margaret's periapsis precession period (Pw) is almost 1.6 million years long.[1]
As of 2008, Margaret's current eccentricity is 0.7979.[5] This temporarily gives Margaret the most eccentric orbit of any moon in the solar system, though Nereid's mean eccentricity is greater.
[edit] See also
[edit] References
- ^ a b Jacobson, R.A. (2003) URA072 (2007-Jun-28). Planetary Satellite Mean Orbital Parameters. JPL/NASA. Retrieved on 2008-01-22.
- ^ a b c d Scott S. Sheppard, David C. Jewitt, and Jan Kleyna An Ultradeep Survey for Irregular Satellites of Uranus: Limits to Completeness, The Astronomical Journal, 129 (2005), pages 518–525 . Preprint
- ^ IAU Circular 8217
- ^ Planetary names USGS.
- ^ IAU-MPC Natural Satellites Ephemeris Service. IAU: Minor Planet Center. Retrieved on 2008-01-26. (Select Uranian, deselect Ephemerides and select Orbital Elements)
[edit] External links
- Margaret Profile by NASA's Solar System Exploration
- David Jewitt pages
- Uranus' Known Satellites (by Scott S. Sheppard)
- Ephemeris IAU-NSES
|
|||||||||||||||||||
