The Sun Planets Solar System Milky Way Galaxy Astronomy Books Universe Data Online Physics reference library

Home |  Library menu |  Periodic table |  Constants |  Chemicals |  Electron energy |  Synonyms |  Math Formulas |  Bookmark

The Planets Solar System

Our Planets Solar System, Milky Way Galaxy and Planet Earth Orbital Data for the Sun

*Negative values of rotation period indicate that the planet rotates in the direction opposite to that in which it orbits the Sun. This is called a retrograde rotation.

The eccentricity (e) is a number which measures how elliptical orbits are. If e=0, the orbit is a circle. All the planets have eccentricities close to 0, so they must have orbits which are nearly circular.

The semi major axis (the average distance to the Sun) is given in units of the Earth's average distance to the Sun, which is called an AU. For example, Neptune is 30 times more distant from the Sun than the Earth, on average. Orbital periods are also given in units of the Earth's orbital period, which is a year.

The Planets, Solar System: Facts and Exploration	The Quest for Alien Planets : Exploring Worlds Outside the Solar System	Astronomy Today, Volume 1: The Solar System	Math in Our Planets, Solar System: Applying Problem-Solving Strategies

Sun Planets Solar System Motion and the Milky way galaxy UVW velocity data

The Great Attractor, in the direction of the Centaurus constellation, attracts a river of galaxies which includes our Milky way along with the Local Group of galaxies and the Virgo cluster, etc., at the speed of about 600,000 m/sec.

Since the direction of the centre of the Galaxy is established by radio measurements and the galactic plane is clearly established by both radio and optical studies, it is possible to determine the motion of the Sun and the solar system with respect to a fixed frame of reference centered at the Galaxy and not rotating. The value for this motion is generally accepted as 225,000 m/s in the direction = 90°.

Hubble has determined the sun's motion with respect to galaxies beyond the Local Group at 300,000 m/s. This motion has taken into consideration the sun's motions within in the Local Group, its neighbors and the sun's rotation around the milky way galactic center.

Galactic UVW Velocity Data for our Sun and solar system:
U Velocity: has definition: The component of a star's U motion away from the Galactic center. If a star moves away from the Galactic center, the star's U velocity is positive; if a star moves toward the Galactic center, the U velocity is negative; and if the star moves neither toward nor away from the Galactic center, the U velocity is zero. The Sun has a U velocity of -9,000 m/s, so the Sun is moving toward the Galactic center at 9,000 m/s.

V Velocity: has definition: A star's V motion in respect to the direction of Galactic rotation, as measured relative to a nearby star that has a circular orbit. If a star revolves faster than such a star, the V velocity is positive; if it revolves more slowly, the V velocity is negative; and if both revolve at the same rate, the V velocity is zero. The Sun has a V velocity of +12,000 m/s, so it revolves 12,000 m/s faster than it would if it had a circular orbit.

W Velocity: has definition: A star's W motion perpendicular to the Galactic plane. If a star is moving up, its W velocity is positive; if a star is moving down, its W velocity is negative; and if a star does neither, its W velocity is zero. The Sun has a W velocity of +7,000 m/s, so it is moving up at 7,000 m/s. In general, the greater a star's W velocity when it crosses the Galactic plane, the farther above and below the plane the star will travel.

Galaxy Astronomy Velocity Data for some of the nearest galaxies

Edwin Hubble tuning fork diagram

Edwin Hubble (1889-1953) introduced the morphological classification scheme for galaxy types. His tuning fork diagram differentiates elliptical from unbarred and barred spirals. Spirals are further subdivided according to the tightness and structure of their spiral arms. Intermediate to the spirals and elliptical is the lenticular or ‘S0’ class. Lenticulars have the same disk-like structure of spirals with an inner nuclear bulge, but lack spiral arms and share the smoothness and colors of the elliptical. Over 90% of nearby galaxies can be categorized within Hubble’s scheme

The nearest galaxy to our own is the Sagittarius galaxy at 24 kilo parsecs. This is fairly close by universal standards, but one parsec is equal to about 3.26 light years (the velocity of light is 299,792,458 meters/second, so 1 pc is the distance traveled by light in 3.26 years).