Orbit and rotation::2 Pallas


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Orbit and rotation

The animation illustrates Pallas's near-18:7 resonance pattern with Jupiter. The motion of Pallas is shown in a reference frame that rotates about the Sun (i.e. the center dot) with a period equal to Jupiter's orbital period. Accordingly, Jupiter's orbit appears almost stationary as the pink ellipse at top left. Mars's motion is orange, and the Earth–Moon system is blue and white. The orbit of Pallas is green when above the ecliptic and red when below. The near-18:7 resonance pattern with Jupiter only marches clockwise: it never halts or reverses course (i.e. no libration).

Pallas has unusual dynamic parameters for such a large body. Its orbit is highly inclined and moderately eccentric, despite being at the same distance from the Sun as the central part of the asteroid belt. Furthermore, Pallas has a very high axial tilt of 84°, with its north pole pointing towards ecliptic coordinates (β, λ) = (30°, −16°) with a 5° uncertainty in the Ecliptic J2000.0 reference frame.<ref name="Carry2009"/> This means that every Palladian summer and winter, large parts of the surface are in constant sunlight or constant darkness for a time on the order of an Earth year, with areas near the poles experiencing continuous sunlight for as long as two years.<ref name=Carry2009/>

Near resonances

Pallas is in a, likely coincidental, near-1:1 orbital resonance with Ceres.<ref name="Goffin2001"/> Pallas also has a near-18:7 resonance (91,000-year period) and an approximate 5:2 resonance (83-year period) with Jupiter.<ref name="Taylor1982"/>

Transits of planets from Pallas

From Pallas, Mercury, Venus, Mars, and Earth can occasionally appear to transit, or pass in front of, the Sun. Earth last did so in 1968 and 1998, and will next transit in 2224. Mercury did in October 2009. The last and next by Venus are in 1677 and 2123, and for Mars they are in 1597 and 2759.<ref name="solex"/>

2 Pallas sections
Intro   History    Orbit and rotation    Physical characteristics    Satellites    Exploration    See also    Notes    References    External links   

Orbit and rotation
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