Angular Momentum in the Solar System
Altitude: the angular distance of a celestial body above or below the horizon, Apparent solar time: the measure of time based on the diurnal motion of the true Sun. Brilliancy: for Mercury and Venus the quantity ks2/r2, where k= (1+cos i ), . It is the difference between the actual angular position in the elliptic orbit and . There is no force that causes the planets to rotate. Angular momentum is given by L=m*w*r2 where m is the mass, w is the Consider a portion of the cloud the collapses from a size of a light year or so to the size of the solar system. . ( Beginner) · What's the difference between astronomy and astrology?. Firstly, strictly speaking, the angular speeds of the planets change with Why are the orbits of planets in the Solar System nearly circular? . and consequently, since the angular velocity ω and orbital period T are related by T = 2 π In fact, Kepler's three laws clearly state the relation between the time to.
Conjunctions are usually tabulated as geocentric phenomena. For Mercury and Venus, geocentric inferior conjunction occurs when the planet is between the Earth and Sun, and superior conjunction occurs when the Sun is between the planet and Earth. Also one of the precisely defined areas of the celestial sphere, associated with a grouping of stars, that the International Astronomical Union has designated as a constellation.
More precisely, culmination is the passage through the point of greatest altitude in the diurnal path. Upper culmination also called "culmination above pole" for circumpolar stars and the Moon or transit is the crossing closer to the observer's zenith.
Lower culmination also called "culmination below pole" for circumpolar stars and the Moon is the crossing farther from the zenith. Besselian day numbers depend solely on the Earth's position and motion: It is measured along the hour circle passing through the celestial object. Declination is usually given in combination with right ascension or hour angle. Correction for this effect, which is independent of wavelength, is included in the reduction from mean place to apparent place.
Deflection of the vertical: Delta T D T: See catalog equinox, equinox, true equator and equinox. See Barycentric dynamical Time: See mean anomaly; true anomaly. An annular eclipse occurs when the apparent disk of the Moon is smaller than that of the Sun.
newtonian mechanics - Angular speed of the planets - Physics Stack Exchange
The eclipse may be total the Moon passing completely through the Earth's umbrapartial the Moon passing partially through the Earth's umbra at maximum eclipseor penumbral the Moon passing only through the Earth's penumbra. It may be total observer in the Moon's umbrapartial observer in the Moon's penumbraor annular.
The ephemeris meridian is 1. InET was replaced by dynamical time. It is the difference between the actual angular position in the elliptic orbit and the position the body would have if its angular motion were uniform. Equation of the equinoxes: See catalog equinox; dynamical equinox for precise usage. This concept is no longer used in high precision work.
The dimensions of k2 are those of Newton's constant of gravitation: See zenith; latitude, terrestrial, longitude, terrestrial. See zenith; latitude, terrestrial; longitude, terrestrial.
On land it is the level surface that would be assumed by water in an imaginary network of frictionless channels connected to the ocean. See apparent place; mean place; aberration, planetary. Greenwich sidereal date GSD: Greenwich sidereal day number: Every year that is exactly divisible by four is a leap year, except for centurial years, which must be exactly divisible by to be leap years.
Thus is a leap year, but and are not leap years. The great circle formed by the intersection of the celestial sphere with a plane perpendicular to the line from an observer to the zenith is called the astronomical horizon.
In the Julian calendar a common year is defined to comprise days, and every fourth year is a leap year comprising days. The Julian calendar was superseded by the Gregorian calendar. January 1, Greenwich noon, Julian proleptic calendar. In precise work the timescale, e.
Julian date, modified MJD: Julian day number JD: This period served as the basis for the Julian calendar. Generally, leap seconds are added at the end of June or December. Physical librations are due to variations in the orientation of the Moon's rotational axis in inertial space. The much larger optical librations are due to variations in the rate of the Moon's orbital motion, the obliquity of the Moon's equator to its orbital plane, and the diurnal changes of geometric perspective of an observer on the Earth's surface.
It is observable when the light from a star or planet passes a massive object such as the Sun. During this interval the motion of the body in space causes an angular displacement of its apparent place from its geometric place see geometric position.
These corrections are due to the irregular surface of the Moon and are a function of the librations in longitude see longitude, celestial and latitude see latitude, celestial and the position angle from the central meridian.
See Spectral types or classes. Magnitude of a lunar eclipse: Magnitude of a solar eclipse: Thus the mean anomaly is the angle from pericenter of a hypothetical body moving with a constant angular speed that is equal to the mean motion.
See true anomaly; eccentric anomaly. Mean elements may serve as the basis for calculating perturbations. Mean equator and equinox: Thus the mean equator and equinox are affected only by precession.
Angular Momentum in the Solar System
Positions in star catalogs are normally referred to the mean catalog equator and equinox see catalog equinox of a standard epoch.
A mean place is determined by removing from the directly observed position the effects of refraction, geocentric and stellar parallax, and stellar aberration see aberration, stellarand by referring the coordinates to the mean equator and equinox of a standard epoch.
In compiling star catalogs it has been the practice not to remove the secular part of stellar aberration see aberration, secular. Prior toit was additionally the practice not to remove the elliptic part of annual aberration see aberration, annual; aberration, E-terms of. For planetary observations a meridian is half the great circle passing through the planet's poles and through any location on the planet.
The position of a node is one of the standard orbital elements see elements, orbital used to specify the orientation of an orbit. Nutation of the Earth's pole is discussed in terms of components in obliquity and longitude see longitude, celestial. For the Earth the obliquity of the ecliptic is the angle between the planes of the equator and the ecliptic.
If the primary source of illumination of a reflecting body is cut off by the occultation, the phenomenon is also called an eclipse. The occultation of the Sun by the Moon is a solar eclipse see eclipse, solar. Osculating elements describe the unperturbed two-body orbit that the body would follow if perturbations were to cease instantaneously. Geocentric diurnal parallax is the difference in direction between a topocentric observation and a hypothetical geocentric observation.
Heliocentric or annual parallax is the difference between hypothetical geocentric and heliocentric observations; it is the angle subtended at the observed object by the semimajor axis of the Earth's orbit.
Anyway, the bottom line is that stars like the Sun spin from the original angular momentum that was there in the solar nebula from which it formed.
International Astronomical Center (IAC)
Not only that, all orbital motion of the planets including the spin is due to this orginal angular momentum. You are saying that original angular momentum of the cloud causes orbital motions and rotations of the planets mostly. But in the case of orbital motions we have gravitational force that gives us some restrictions of movement Kepler laws,for example.
What I am saying is that there will be no planets if there was no initial angular momentum in the primordial solar nebula. If a nebula with absolutely no rotation collapses, then there will only be a central non-rotating star and there will not be any planets. Planets form out of a protostellar disk, which itself forms only because of the initial angular momentum of the cloud.
The dynamics of a rotating body is of course controlled by forces like gravity. Kepler's laws are a direct consequence of gravity. Are there some laws also in the case of rotations? The only thing that has to be kept in mind in rotation is that it results in a centrifugal acceleration that points radially from the center of motion.
- International Astronomical Center
Hence, there has to be some force that conteracts this acceleration; otherwise the body will fly away in case of orbital motion or will disintegrate in case of spinning.
In the case of orbital motion, the counteracting force is gravity; gravity causes the body to continually fall towards the center, and this exactly conteracts the force resulting from the centripetal acceleration. In the case of a spinning object, it is the self-adhesion of the body itself that keeps it together.