The Solar System consists of the Sun and the other celestial objects gravitationally bound to it: the eight planets, their 168 known moons, five currently identified dwarf planets and their seven known moons, and billions of small bodies. This last category includes asteroids, Kuiper belt objects, comets, meteoroids and interplanetary dust. In broad terms, the charted regions of the Solar System consist of the Sun, four terrestrial inner planets, an asteroid belt composed of small rocky bodies, four gas giant outer planets, and a second belt, called the Kuiper belt, composed of icy objects. Beyond the Kuiper belt lies the scattered disc, the heliopause, and ultimately the hypothetical Oort cloud. In order of their distances from the Sun, the planets are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Six of the eight planets are in turn orbited by natural satellites, usually termed "moons" after Earth's Moon, and each of the outer planets is encircled by planetary rings of dust and other particles. All the planets except Earth are named after gods and goddesses from Greco-Roman mythology. The five dwarf planets are Pluto, Makemake, and Haumea, the three largest known Kuiper belt objects; Ceres, the largest object in the asteroid belt; and Eris, the largest known object in the scattered disc.
Earth (pronounced /ɜrθ/) is the third planet from the Sun and is the largest of the terrestrial planets in the Solar System, in both diameter and mass. Home to the human species, it is also referred to as "the Earth", "Planet Earth", " Gaia", " Terra", "the World", and "the Blue Planet".
The Earth is the first planet known to have liquid water on the surface and is the only place in the universe known to harbor life. Earth has a magnetic field that, together with a primarily nitrogen-oxygen atmosphere, protects the surface from radiation that is harmful to life. The atmosphere also serves as a shield that causes smaller meteors to burn up before they strike the surface.
The Earth formed around 4.57 billion years ago and its only known natural satellite, the Moon, began orbiting it around 4.53 billion years ago. At present, the Earth orbits the Sun once for every roughly 366.26 times it rotates about its axis (which is equal to 365.26 solar days). The Earth's axis of rotation is tilted 23.5° (away from the perpendicular to its orbital plane), producing seasonal variations on the planet's surface.
- ... that Jupiter is the only planet capable of pulling an interstellar comet into a Sun-centered orbit?
- ...that the Solar Sentinels, a NASA spacecraft designed to study the Sun, will have to survive at distances from the Sun only one-quarter of Earth's distance?
- ...that just over 50 kilometres above its surface, the atmosphere of Venus has very similar pressure and temperature as does Earth, making it the most Earth-like area in the solar system?
- ...that NASA conducts field trials, called Desert RATS, for new technologies for manned exploration of the surface of the Moon, Mars, or beyond?
- ...that the south pole of the planet Mercury is located in the Bach quadrangle?
- ...that the Sweden Solar System is currently the world's largest scale model of the solar system?
- ...that the dominant feature in the Shakespeare quadrangle is the 1300 km wide Caloris Planitia, the largest and best preserved impact basin on Mercury observed by the spacecraft Mariner 10?
- ...that the nearly circular shape of Lukanga Swamp, a wetland covering 2,600 km² in Central Province, Zambia, has led to speculation that it may be a crater formed by the impact of a meteorite?
- ... that with the diameter of 715 km (444 mi) Rembrandt (pictured) is the second largest impact crater on Mercury?
- ...that the European and Japanese collaborative BepiColombo mission is planned to be the first extensive mission to Mercury since Mariner 10? (Computer rendition of the BepiColombo orbiters)
- ... that the Valhalla structure (pictured) on Jupiter's moon Callisto is the largest multi-ring basin in the Solar System?
- ... that Frank J. Low, an infrared astronomy pioneer, used data from an infrared telescope flown on a Learjet to show that planets Jupiter and Saturn generate and emit internal energy into space?
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