Solar System

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The Solar System[a] consists of the Sun and those celestial objects bound to it by gravity, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The Sun's retinue of objects circle it in a nearly flat disc called the ecliptic plane, most of the mass of which is contained within eight relatively solitary planets whose orbits are almost circular. The four smaller inner planets; Mercury, Venus, Earth and Mars, also called the terrestrial planets, are primarily composed of rock and metal. The four outer planets, Jupiter, Saturn, Uranus and Neptune, also called the gas giants, are composed largely of hydrogen and helium and are far more massive than the terrestrials.

The Solar System is also home to two main belts of small bodies. The asteroid belt, which lies between Mars and Jupiter, is similar to the terrestrial planets as it is composed mainly of rock and metal. The Kuiper belt (and its subpopulation, the scattered disc), which lies beyond Neptune's orbit, is composed mostly of ices such as water, ammonia and methane. Within these belts, five individual objects, Ceres, Pluto, Haumea, Makemake and Eris, are recognised to be large enough to have been rounded by their own gravity, and are thus termed dwarf planets. The hypothetical Oort cloud, which acts as the source for long-period comets, may also exist at a distance roughly a thousand times beyond these regions.

Within the Solar System, various populations of small bodies, such as comets, centaurs and interplanetary dust, freely travel between these regions, while the solar wind, a flow of plasma from the Sun, creates a bubble in the interstellar medium known as the heliosphere, which extends out to the edge of the scattered disc.

Six of the planets and three of the dwarf planets are orbited by natural satellites, usually termed "moons" after Earth's Moon. Each of the outer planets is encircled by planetary rings of dust and other particles.

For more information about Solar System, read the full article at Wikipedia.
This text uses material from Wikipedia and is available under the GNU Free Documentation License.

News tagged with solar system

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Professor: We have a 'moral obligation' to seed universe with life

Space & Earth / Astronomy

Feb 09, 2010 | 3.1 / 5 (27) | 55 |

(PhysOrg.com) -- Eventually, the day will come when life on Earth ends. Whether that’s tomorrow or five billion years from now, whether by nuclear war, climate change, or the Sun burning up its fuel, the last ...

Powering cube satellites

Space & Earth / Space Exploration

Feb 03, 2010 | 3.9 / 5 (13) | 11

Right now, 10 to 15 Rubik's Cube-sized satellites are orbiting high above Earth. Known as cube satellites, or "CubeSats," the devices help researchers conduct simple space observations and measure characteristics ...

Craters young and old in Sirenum Fossae

Space & Earth / Space Exploration

Feb 03, 2010 | 3.8 / 5 (4) | 1

The Mars Express High Resolution Stereo Camera has imaged craters both young and old in this view of the Southern Highlands of Mars.

Obama's budget slashes moon mission, new rockets

Space & Earth / Space Exploration

Jan 27, 2010 | 4.6 / 5 (9) | 28

NASA's plans to return astronauts to the moon are dead. So are the rockets being designed to take them there -- that is, if President Barack Obama gets his way.

The First of Many Asteroid Finds for WISE

Space & Earth / Space Exploration

Jan 25, 2010 | 4.8 / 5 (4) | 0 |

(PhysOrg.com) -- NASA's Wide-field Infrared Survey Explorer, or WISE, has spotted its first never-before-seen near-Earth asteroid, the first of hundreds it is expected to find during its mission to map the ...

The Floor of Tycho Crater

Space & Earth / Space Exploration

Jan 14, 2010 | 5 / 5 (1) | 0

(PhysOrg.com) -- Tycho Crater is an one of the most prominent craters on the moon. It appears as a bright spot in the southern highlands with rays of bright material that stretch across much of the nearside. ...

Dunes of Sand: Resumed Mars Orbiter Observations Yield Stunning Views

Space & Earth / Space Exploration

Jan 14, 2010 | 5 / 5 (7) | 1 |

(PhysOrg.com) -- Dunes of sand-sized materials have been trapped on the floors of many Martian craters. This view shows dunes inside a crater in Noachis Terra, west of the giant Hellas impact basin in Mars' ...

Solar System Shield

Space & Earth / Space Exploration

Jan 14, 2010 | 4.5 / 5 (4) | 0 |

Water vapor in planet-forming disks may block ultraviolet radiation from destroying water and other important molecules for life, according to new calculations.

Land Ho! Huygens Plunged to Titan Surface 5 Years Ago

Space & Earth / Space Exploration

Jan 14, 2010 | 4.7 / 5 (9) | 3 |

(PhysOrg.com) -- The Huygens probe parachuted down to the surface of Saturn's haze-shrouded moon Titan exactly five years ago on Jan. 14, 2005, providing data that scientists on NASA's Cassini mission to Saturn ...

VLT captures first direct spectrum of an exoplanet

Space & Earth / Astronomy

Jan 13, 2010 | 5 / 5 (9) | 5 |

(PhysOrg.com) -- By studying a triple planetary system that resembles a scaled-up version of our own Sun’s family of planets, astronomers have been able to obtain the first direct spectrum -- the “chemical ...

Solar Scientists Use 'Magnetic Mirror Effect' to Reproduce IBEX Observation

Space & Earth / Astronomy

Jan 12, 2010 | 4.7 / 5 (7) | 0 |

(PhysOrg.com) -- Ever since NASA's Interstellar Boundary Explorer, or IBEX, mission scientists released the first comprehensive sky map of our solar system's edge in particles, solar physicists have been busy ...

Deep heat powers once-in-a-billion-year volcanoes on icy moon

Space & Earth / Space Exploration

Jan 11, 2010 | 4.6 / 5 (11) | 7 |

(PhysOrg.com) -- New research by Macquarie University planetary scientist Dr Craig O’Neill and US colleague Francis Nimmo has found the answer to an apparent cosmic contradiction.

Mirror Testing at NASA Breaks Superstitious Myths

Space & Earth / Space Exploration

Jan 07, 2010 | 4 / 5 (6) | 0

(PhysOrg.com) -- In ancient mythological times reflective surfaces like shiny metals and mirrors were thought to be magical and credited with the ability to look into the future. NASA is using mirrors to do ...

First Earth-like planet spotted outside solar system likely a volcanic wasteland

Space & Earth / Astronomy

Jan 06, 2010 | 5 / 5 (10) | 26 |

(PhysOrg.com) -- When scientists confirmed in October that they had detected the first rocky planet outside our solar system, it advanced the longtime quest to find an Earth-like planet hospitable to life. The rocky planet ...