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1) Mean distance between the Earth and the Sun: 1.495985 × 1011 m.
2) The AU is the preferred unit for distances within the solar system. Mercury, the innermost planet, lies on average 0.39 AU from the Sun; Pluto, normally the farthest planet, lies on average 39.5 AU from the Sun.
3) The mean distance between the Earth and the Sun. The astronomical unit is defined as the length of the radius of the unperturbed circular orbit of a body of negligible mass moving around the Sun with a sidereal angular velocity of 0.017202098950 radian per day of 86400 ephemeris seconds. AU = 1.496 × 1013 cm ≈ 500 lt-sec.
4) The mean distance from the earth to the sun, equal to 92.81 million miles or 499.012 light-seconds.
5) The radius of a circular orbit in which a body of negligible mass, and free of perturbations, would revolve around the Sun in 2π / k days, where k is the Gaussian gravitational constant. This is slightly less than the semi-major axis of the Earth's orbit.
Industry:Astronomy
The science that studies the physics and chemistry of extraterrestrial objects. The alliance of physics and astronomy, which began with the advent of spectroscopy, made it possible to investigate what celestial objects are and not just where they are.
Industry:Astronomy
The total number of protons and neutrons in an atom's nucleus. For example, oxygen-16 has a mass number of sixteen, because it has eight protons and eight neutrons.
Industry:Astronomy
The first star other than the Sun to have its parallax, and hence distance, measured. The star is a double orange dwarf.
Industry:Astronomy
Trojan asteroid (60° ahead of Jupiter. It was the first Trojan to be discovered.
Industry:Astronomy
The theory by which planetesimals are assumed to collide with one another and coalesce, eventually sweeping up enough material to form the planets.
Industry:Astronomy
1) Active galactic nuclei are very luminous. Their energy output is in two forms: nonthermal continuum and thermal emission line.
2) Any galaxy which is emitting large quantities of non-thermal radiation.
Industry:Astronomy
Controlling the shape of a telescope mirror at a relatively slow rate.
Industry:Astronomy
