http://apod.nasa.gov/apod/ap080923.html
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http://en.wikipedia.org/wiki/Haumea_(dwarf_planet)
<<Haumea is a dwarf planet in the Kuiper belt, roughly one-third the mass of Pluto. It was classified as a dwarf planet by the International Astronomical Union and named after the Hawaiian goddess of childbirth and fertility. Although it is not spherical, Haumea is considered a dwarf planet because it is in hydrostatic equilibrium: its ellipsoidal shape is due to its rapid rotation (in much the same way as a water balloon stretches out when tossed) and not due to insufficient self-gravity. Prior to being given the name Haumea, it had been assigned the temporary designation of (136108) 2003 EL61. In their own work, Mike Brown's team at Caltech had used the nickname "Santa" as they first observed the object on December 28, 2004, just after Christmas. Because Haumea rotates roughly once every four hours, faster than any other known body in the solar system larger than 100 km in diameter, it should be distorted into a triaxial ellipsoid. The short rotation period of Haumea is likely to have been caused by a giant impact, which also created its satellites.
Dimensions ~1960 × 1518 × 996 km
Mean density 2.6–3.3 g/cm³
Sidereal rotation : (3h 55m)>>
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henk21cm wrote: Lets try to counterbalance the centrifugal force by the equitorial gravitational force.
ω² R = g ................................ (Eq. 1)
with g the acceleration of gravity. With ω = 2 π/T this leads with (1) to:
T ≅ 2 √ (R)
if we approximate π² by g. T is de axial rotation period of the earth. With R = 6.5E6 m, T ≅ 5100 s: 1h 25m.
A spherical earth rotating this fast (period ~ 1h 25m) would tear itself apart by centrifugal force. Long before the catastrophic rotational rate of self destruction (period ~ 3h 50m), however, the earth would elongate into a prolate spheroid [like the large Kuiper belt object "Santa" (period ~ 3h 55m)].
http://en.wikipedia.org/wiki/(136108)_2003_EL61
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Phase locked satellites elongate and tear apart at even slower rotation rates (period ~ 5h 25m) because differential gravity gradients are equally important (to centrifugal forces).
Neptune's Naiad (period = 7 h 4 min)
http://en.wikipedia.org/wiki/Naiad_%28moon%29
Mars Phobos (period = 7 h 39 min)
http://en.wikipedia.org/wiki/Phobos_%28moon%29
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Only
very small rigid solid asteroids or moons can rotate faster:
1998 KY26 (period = 10.7 minutes)
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http://spacewatch.lpl.arizona.edu/1998ky26.html
<<The asteroid 1998 KY26 was discovered by Tom Gehrels on the night of May 28, 1998 (UT) during a routine scanning session. Although appearing as a small dot on the screen like any other asteroid, this near-Earth asteroid has some interesting properties. First, it passed close enough to the Earth for radar observations to be taken. From light curve measurements, its rotation period was calculated to be 10.7 minutes - the fastest rotating asteroid known. In fact, it is the fastest known rotating body in the solar system! >>