Celestial mechanics Reference Libraries

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Escape Velocity
2004-10-19 04:45:41

Escape Velocity -- An escape velocity is the minimum speed at which an object without propulsion can move away from a source of a gravitational field indefinitely if there is no friction. This definition may need modification for the practical problem of two or more sources in some cases. In any case, the object is assumed to be a point with a mass that is negligible compared with that of...

2004-10-19 04:45:41

Ecliptic -- The ecliptic is the geometric plane that contains the orbit of the Earth. The orbits of most planets in the Solar System lie very close to it. Seen from the Earth, this is the great circle on the celestial sphere that contains the different positions of the Sun relative to the background stars throughout the year, and most planets can be seen close this circle. The zodiac...

Circumpolar Star
2004-10-19 04:45:41

Circumpolar Star -- Circumpolar stars are those stars which are located near the poles of the celestial sphere. As the Earth rotates, the sky appears to rotate; and most stars will be hidden below the horizon at some point in their circular paths. A circumpolar star is near enough to the celestial pole that it will never go under the horizon. It will therefore be visibile for all the night,...

Kuiper Belt
2004-10-19 04:45:41

Kuiper Belt -- The Kuiper belt is an area of the solar system extending outwards from the orbit of Neptune (at 30 AU) to 50 AU. The largest of the objects in the Kuiper belt are the planet Pluto and its moon Charon. A new Kuiper belt object, currently called 2001 KX76, has been found that is about the size of Charon, and larger than Ceres. Another such object, Quaoar, discovered in 2002,...

Neptunes Moon Triton
2004-10-19 04:45:41

Planet Triton -- Triton is the planet Neptune's largest moon, discovered by William Lassell in 1846 just 17 days after the planet itself was discovered. It is named after Triton, from Greek mythology. Triton is unique among all large moons in the solar system for its retrograde orbit around the planet (i.e., it orbits in a direction opposite to the planet's rotation). Jupiter's moons...

Saturns Moon Hyperion
2004-10-19 04:45:41

Saturn's moon Hyperion -- Hyperion is a moon of Saturn discovered by Bond and Lassell in 1848. It is the largest highly irregular (non-spherical) body in the solar system (Proteus is quite a bit larger but is almost spherical). It seems likely that Hyperion is a fragment of a larger body that was broken by a large impact in the distant past. The largest crater on its surface is approximately...

2004-10-19 04:45:40

The Planet Mercury -- in astronomy, nearest planet to the sun, at a mean distance of 36 million mi (58 million km); its period of revolution is 88 days. Mercury passes through phases similar to those of the moon as it completes each revolution about the sun, although the visible disk varies in size with respect to its distance from the earth. Because its greatest elongation is 28, it is seen...

Near-Earth Asteroid
2004-10-19 04:45:40

Near-Earth Asteroid -- Near-Earth asteroids (NEAs) are asteroids whose orbit intersects Earth's orbit and which may therefore pose a collision danger, as well as being most easily accessible for spacecraft from Earth. In fact, some near-Earth asteroids can be reached with much less ΔV than the Moon. The most famous near-Earth asteroid is 433 Eros that was visited by NASA's Near Earth...

Word of the Day
  • A member of the swell-mob; a genteelly clad pickpocket. Sometimes mobsman.
Use of the word 'swell-mobsman' dates at least to the early 1800s.