1 Ceres ([ˈsi.riz], Latin Cerēs) was the first asteroid to be discovered. It was discovered on January 1, 1801, by Giuseppe Piazzi. With a diameter of about 950 km it is by far the largest and most massive asteroid in the asteroid belt: It is over half as massive as the rest of the belt put together. 1 Ceres - Name. Ceres was originally named Ceres Ferdinandea after both the mythological figure Ceres (Roman goddess of plants and motherly ...

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1 Ceres - Name 1 Ceres - Discovery 1 Ceres - Physical characteristics 1 Ceres - Observations 1 Ceres - Trivia 1 Ceres - Aspects 1 Ceres - External link

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See also:

Prograde and retrograde motion, Prograde and retrograde motion - Two notations, Prograde and retrograde motion - Retrograde orbits, Prograde and retrograde motion - Retrograde rotation, Prograde and retrograde motion - Retrogradation or apparent retrograde motion, Prograde and retrograde motion - Examples, Prograde and retrograde motion - Reference

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Mars has no global geomagnetic field comparable to Earth's. Combined with a thin atmosphere, this increases the amount of ionizing radiation that reaches the Martian surface. The Mars Odyssey spacecraft carried an instrument, the Mars Radiation Environment Experiment (MARIE), to measure the dangers to humans. MARIE found that radiation levels in orbit above Mars are 2.5 times higher than at the International Space Station. Average doses were about 22 millirads per day (220 micrograys per day or 0.8 gray per year). A three year exposure to su ...

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Colonization of Mars, Colonization of Mars - Similarity to Earth, Colonization of Mars - Differences, Colonization of Mars - Habitability, Colonization of Mars - Radiation, Colonization of Mars - Communication, Colonization of Mars - Possible locations for colonies, Colonization of Mars - Polar regions, Colonization of Mars - Midlands, Colonization of Mars - Valles Marineris, Colonization of Mars - Concerns

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The celestial equator is a great circle on the imaginary celestial sphere, which is actually the plane of the terrestrial equator extended out into the universe (i.e., it could be constructed by extrapolating the Earth's equator until it touches the celestial sphere). The celestial equator is inclined by ~23.5°, with respect to the ecliptic plane; a result of axial tilt. Celestial objects near the celestial equator are visible worldwide, b ...

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Earth, also known as Terra, and Tellus mostly in the 19th century, is the third-closest planet to the Sun. It is the largest of the solar system's terrestrial planets, and the only planetary body that modern science confirms as harboring life. Scientific evidence indicates that the planet formed around 4.57 billion (4.57×109) years ago, and shortly thereafter (4.533 billion years ago) acquired its single natural satellite, the Moon. Earth - Lexicography. Its astronomical symbol con ...

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Earth - Lexicography Earth - Physical characteristics Earth - Earth in the solar system
Earth - The Moon
Earth - Geography Earth - Environment and Ecosystem
Earth - Climate Earth - Terrain Earth - Natural resources Earth - Land use Earth - Natural and environmental hazards Earth - Human geography
Earth - Descriptions of Earth

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Mars has an axial tilt of 25.2°, quite close to the value of 23.45° for Earth, and thus Mars has seasons of spring, summer, autumn, winter as Earth does (if the axial tilt was 0° there would be no seasons). As on Earth, the southern and northern hemispheres have summer and winter at opposing times. However, the orbit of Mars has significantly greater eccentricity than that of Earth. Therefore the seasons are of unequal length, much more so than on Earth: In practical terms, this means that summers and winters have different ...

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Astronomy on Mars - Seasons Astronomy on Mars - The color of the sky Astronomy on Mars - Astronomical phenomena
Astronomy on Mars - Earth and Moon Astronomy on Mars - Phobos and Deimos Astronomy on Mars - Meteors and meteor showers Astronomy on Mars - Auroras Astronomy on Mars - Celestial poles and ecliptic Astronomy on Mars - Long-term variations

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Prograde motion is the rotational or orbital motion of a body in a direction similar to that of other bodies within a given system, and is sometimes called direct motion. Retrograde motion is in the contrary direction. The word 'retrograde' derives from the Latin words retro, backwards, and gradus, step. Prograde and retrograde motion - Two notations. The north orbital pole of a celestial body is defined by the right-hand rule: If you curve the fingers of your right hand a ...

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Prograde and retrograde motion - Two notations Prograde and retrograde motion - Retrograde orbits Prograde and retrograde motion - Retrograde rotation Prograde and retrograde motion - Retrogradation or apparent retrograde motion Prograde and retrograde motion - Examples Prograde and retrograde motion - Reference

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Tycho Brahe, born Tyge Ottesen Brahe (December 14, 1546 – October 24, 1601), was a Danish nobleman astrologer and astronomer as well as an alchemist. He was granted an estate on the island of Hven and the funding to build the Uraniborg, an early research institute, where he built large astronomical instruments and took many careful measurements. As an astronomer, Tycho worked to combine what he saw as the geometrical benefits of the Copernican system with the philosophical benefits of the Ptolemaic system into his own model o ...

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Tycho Brahe - Early years Tycho Brahe - Death of his father Tycho Brahe - Family life Tycho Brahe - Nova Tycho Brahe - Heliocentrism Tycho Brahe - Uraniborg Stjerneborg and Benátky nad Jizerou Tycho Brahe - Tycho and astronomy Tycho Brahe - Tycho and Astrology Tycho Brahe - Tycho's moose Tycho Brahe - Tycho's death Tycho Brahe - Named after Tycho

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Solstice is an astronomical term regarding the position of the Sun in relation to the earth's equator. The name is derived from Latin solstitium (from sol: "sun" and sistere: "stand still"). During the year, the position of the sun seen from earth moves North and South. When it changes direction it stands still momentarily. So solstices are those moments of the year when the sun reaches its southernmost or northernmost position, ...

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Solstice - Behaviour of the sun
Solstice - June solstice Solstice - December solstice

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The Arctic Circle is one of the five major circles of latitude that mark maps of the Earth. This is the parallel of latitude that (in 2000) runs 66° 33' 39" north of the Equator. Everything north of this circle is known as the Arctic, and the zone just to the south of this circle is the Northern Temperate Zone. The Arctic Circle marks the southern extremity of the polar day of the summer solstice in June and the polar night of the winter solstice in December. Within the Arctic Circle, the arctic Sun is above the horizon for at ...

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The Voyager 2 spacecraft was launched in 1977. It is identical to its sister Voyager program craft, Voyager 1, but Voyager 2 followed a somewhat different trajectory during its Saturn encounter, bypassing a close encounter with Titan to take advantage of a gravitational slingshot to travel on to Uranus and Neptune. It thus became the first and so far only probe to visit those two planets and the first spacecraft to make the Grand Tour of Jupiter, Saturn, Uranus and Neptune. This was possible only due to a rare geometric arrangement of those four pl ...

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Voyager 2 - Mission planning and launch Voyager 2 - Jupiter Voyager 2 - Saturn Voyager 2 - Uranus Voyager 2 - Neptune Voyager 2 - Escaping the solar system Voyager 2 - Current Position Voyager 2 - Current Voyager 2 data processing and operations Voyager 2 - Voyager 2 in fiction and popular culture

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The North Pole is the northernmost point on any planet. There are various ways of defining a planet's North Pole. Earth's North Pole, however it is defined, lies in the Arctic Ocean. North Pole - Defining the North Pole of Earth. The North Pole, the northernmost point on the Earth, can be defined in four different ways. Only the first two definitions are commonly used. However it is defined, the North Pole lies in the Arctic Ocean. The Geographic North Pole, also known as True ...

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North Pole - Defining the North Pole of Earth North Pole - Geographic North Pole
North Pole - Expeditions
North Pole - Magnetic North North Pole - Geomagnetic North Pole North Pole - Northern Pole of Inaccessibility North Pole - Defining North Poles in astronomy North Pole - Day and night North Pole - Territorial claims to the North Pole Arctic North Pole - Magnetic declination North Pole - Cultural references to the North Pole

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6 Hebe (hee'-bee, Greek ‘Ήβη) is one of the largest Main belt asteroids, and is probably the parent body of the H chondrite meteorites, which account for a remarkable 40% of all meteorites striking the Earth. 6 Hebe - Discovery. Hebe was the sixth asteroid to be discovered, on July 1, 1847. It was the second and final asteroid discovery by Karl Ludwig Hencke, who had previously found 5 Astraea. The name "Hebe" was proposed by Carl Friedrich Gauss, and refers to the Greek goddess of youth, ...

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6 Hebe - Discovery 6 Hebe - Major meteorite source 6 Hebe - Physical characteristics 6 Hebe - Jebe 6 Hebe - Aspects

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7 Iris (eye'-ris) is one of the largest main belt asteroids. 7 Iris - Discovery and name. It was the seventh asteroid discovered, on August 13, 1847 by J. R. Hind from London, UK. It was Hinds' first asteroid discovery. Iris was named after the rainbow goddess Iris of Greek mythology, sister of the Harpies and messenger of the gods, especially Hera. Her quality of attendant of Hera was particularly appropriate to the circumstances of discovery, as she was spotted following 3 Juno (Juno is the ...

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7 Iris - Discovery and name 7 Iris - Characteristics 7 Iris - Aspects

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Cycles are series of states or conditions that repeat themselves, usually after a regular or nearly regular period. Cyclic behaviour is one kind — the simplest, one could say — of oscillation. The standard mathematical model of a cycle is the periodic function. Mathematicians study both periodic functions and almost periodic functions. Cycles may be due to restorative forces causing repetition as in simple harmonic motion, regularity of motion such as daily, monthly, yearly, and other astronomical cycles, or being affected by something else that has these qualities. These for ...

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Cycle studies - History Cycle studies - Astronomy Cycle studies - Social sciences

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5 Astraea (as-tree'-a; written Astræa in the early scientific literature) is a large main belt asteroid. Its surface is highly reflective (bright) and its composition is probably a mixture of nickel-iron with magnesium- and iron-silicates. Astraea was the fifth asteroid discovered, on December 8, 1845 by K. L. Hencke. It was his first of two asteroid discoveries. The second was 6 Hebe. An amateur astronomer and post office employee, Hencke was looking for 4 Vesta when he stumbled on Astraea. The King of Prussia awarded him with an annual pens ...

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5 Astraea - Aspects

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4 Vesta (ves'-tə, IPA /ˈvɛstə/) is the second most massive asteroid in the asteroid belt, with a mean diameter of about 530 km and an estimated mass 12% the mass of the entire asteroid belt. Its size and unusually bright surface make Vesta the brightest asteroid, and the only one ever visible to the naked eye from Earth, apart from 1 Ceres under exceptional viewing conditions. Due to the availability of rock samples in the form of the HED meteorites, it has also been the ...

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4 Vesta - Discovery 4 Vesta - Physical characteristics 4 Vesta - Geology 4 Vesta - Surface features 4 Vesta - Further details 4 Vesta - Aspects

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2 Pallas (pal'-us, Greek Παλλάς) was the second asteroid discovered, following 1 Ceres. It was found and named by H. Wilhelm Olbers on March 28, 1802. It is estimated that it contains 9% of the mass of the entire asteroid belt. 2 Pallas - Name. The asteroid is named after Pallas, the daughter of Triton and friend of Athena in Greek mythology. (There are several male characters of the same name in Greek mythology, but the first asteroids were invariably given female names.) Accordi ...

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2 Pallas - Name 2 Pallas - Characteristics 2 Pallas - Observations 2 Pallas - Trivia 2 Pallas - Aspects 2 Pallas - External link

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3 Juno (jew'-noh) was the third asteroid to be discovered and is one of the largest main belt asteroids. It was was discovered on September 1, 1804 by German astronomer Karl L. Harding, using a humble 2-inch telescope. It was named after the mythological figure Juno, the highest Roman goddess. The adjectival form of the name is Junonian. 3 Juno - Characteristics. Juno is close to being the seventh largest asteroid (it cannot currently be ranked relative to 52 Europa, with a mass approximately ...

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3 Juno - Characteristics 3 Juno - Observations 3 Juno - Aspects

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The ecliptic plane is the geometric plane that contains the orbit of the Earth. The ecliptic is the intersection of the ecliptic plane and the celestial sphere. A more intuitive definition would be to say that the ecliptic is the apparent path of the Sun during a year as seen from Earth. The orbits of most planets in the Solar System lie very close to it. Seen from the Earth, this is a bisecting great circle, superimposed upon the celestial sphere, which contains the different points of the Sun's path, relative to the backgroun ...

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