Margaret is the only known prograde

irregular satellite In astronomy, an irregular moon, irregular satellite or irregular natural satellite is a natural satellite following a distant, inclined, and often eccentric and retrograde orbit. They have been captured by their parent planet, unlike regular s ...

of the

moons of Uranus Uranus, the seventh planet of the Solar System, has 27 known moons, most of which are named after characters that appear in, or are mentioned in, the works of William Shakespeare and Alexander Pope. Uranus's moons are divided into three groups: t ...

. It was discovered by

Scott S. Sheppard Scott Sander Sheppard (born 1977) is an American astronomer and a discoverer of numerous moons, comets and minor planets in the outer Solar System. He is an astronomer in the Department of Terrestrial Magnetism at the Carnegie Institution for Scie ...

, et al. in 2003 and given the

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 The provisional designation is usually superseded by a permanent designation once a reliable orbit has been calcu ...

S/2003 U 3. Confirmed as Uranus XXIII, it was named after the servant of Hero in

William Shakespeare William Shakespeare ( 26 April 1564 – 23 April 1616) was an English playwright, poet and actor. He is widely regarded as the greatest writer in the English language and the world's pre-eminent dramatist. He is often called England's nation ...

's play ''

Much Ado About Nothing ''Much Ado About Nothing'' is a comedy by William Shakespeare thought to have been written in 1598 and 1599.See textual notes to ''Much Ado About Nothing'' in ''The Norton Shakespeare'' ( W. W. Norton & Company, 1997 ) p. 1387 The play ...

''.

Orbit

Margaret stands out as the only prograde irregular satellite of Uranus. The diagram illustrates the orbital parameters of Margaret, unique among the

s of Uranus, with

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...

on the vertical axis and the

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-center, in geometry * Eccentricity (graph theory) of a v ...

of the orbits represented by the segments extending from the

pericentre An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary (astronomy), primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two ...

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. 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 (P_w) is almost 1.6 million years long. Margaret itself may be ejected from the Uranian system in the far future. Margaret's orbit is subject to solar and planetary perturbations; thus, its orbital elements are variable over short timescales. Over a timescale of 8,000 years, the average

orbital eccentricity In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values betwee ...

of Margaret is 0.68. In 2010, its eccentricity grew to 0.81, temporarily making Margaret with the most eccentric orbit of any moon in the Solar System, though

Nereid In Greek mythology, the Nereids or Nereides ( ; grc, Νηρηΐδες, Nērēḯdes; , also Νημερτές) are sea nymphs (female spirits of sea waters), the 50 daughters of the 'Old Man of the Sea' Nereus and the Oceanids, Oceanid Doris ...

's average eccentricity of 0.75 is greater.

References

External links

Margaret Profile
b
NASA's Solar System Exploration

(by

)
Ephemeris IAU-NSES
{{DEFAULTSORT:Margaret (Moon) Moons of Uranus Irregular satellites Discoveries by Scott S. Sheppard 20030829 Moons with a prograde orbit

Orbit

See also

References

External links