Planets in astrology

Ceres is the smallest identified dwarf planet in the solar system, but is significantly the largest object in the asteroid belt. It was discovered on 1 January 1801 by Giuseppe Piazzi, and is named after Ceres, the Roman goddess of growing plants, the harvest, and of motherly love. It was the first asteroid discovered, taking up about one-third of the entire mass of its asteroid belt. The classification of Ceres has changed more than once and has been the subject of some disagreement. Johann Elert Bode believed Ceres to be the "missing planet" he had proposed to exist between Mars and Jupiter, at a distance of 419 million km (2.8 AU) from the Sun.

Earth mass

mass of Earthmass of the EarthEarth's mass
The ratio of Earth mass to lunar mass has been measured to great accuracy. The current best estimate is: : The G product for the Earth is called the geocentric gravitational constant and equals 398600441.8 m 3 s −2. It is determined using laser ranging data from Earth-orbiting satellites, such as LAGEOS-1. The G product can also be calculated by observing the motion of the Moon or the period of a pendulum at various elevations. These methods are less precise than observations of artificial satellites.

Crust (geology)

crustEarth's crustcrustal
This is the most common type of crust in the Solar System. Most of the surfaces of Mercury, Venus, Earth, and Mars comprise secondary crust, as do the lunar maria. On Earth, we see secondary crust forming primarily at mid-ocean spreading centers, where the adiabatic rise of mantle causes partial melting. Tertiary crust is more chemically-modified than either primary or secondary. It can form in several ways: The only known example of tertiary crust is the continental crust of the Earth. It is unknown whether other terrestrial planets can be said to have tertiary crust, though the evidence so far suggests that they do not.


NH 3 anhydrous ammonialiquid ammonia
Ammonia is also found throughout the Solar System on Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto, among other places: on smaller, icy bodies such as Pluto, ammonia can act as a geologically important antifreeze, as a mixture of water and ammonia can have a melting point as low as 173 K if the ammonia concentration is high enough and thus allow such bodies to retain internal oceans and active geology at a far lower temperature than would be possible with water alone. Substances containing ammonia, or those that are similar to it, are called ammoniacal. Ammonia is a colourless gas with a characteristic pungent smell. It is lighter than air, its density being 0.589 times that of air.

List of minor-planet groups

groupdynamical groupasteroid group
The largest appears to be 5261 Eureka. Many of the Earth-, Venus-, and Mercury-crosser asteroids have aphelia greater than 1 AU. Inner asteroid belt, inside of the strong Kirkwood gap at 2.50 AU due to the 3:1 Jupiter orbital resonance. The largest member is 4 Vesta. It apparently also includes a group called the main-belt I asteroids which have a semi-major axis between 2.3 AU and 2.5 AU and an inclination of less than 18°. Middle (or intermediate) asteroid belt, between the 3:1 and 5:2 Jupiter orbital resonances, the latter at 2.82 AU. The largest member is Ceres. This group is apparently split into the:.


The unit definition does not vary with location—the g-force when standing on the Moon is almost exactly 1⁄6 that on Earth. The unit g is not one of the SI units, which uses "g" for gram. Also, "g" should not be confused with "G", which is the standard symbol for the gravitational constant.

20th century

twentieth century20th20th centuries
The age of the Solar System, including Earth, was determined, and it turned out to be much older than believed earlier: more than 4 billion years, rather than the 20 million years suggested by Lord Kelvin in 1862. The planets of the Solar System and their moons were closely observed via numerous space probes. Pluto was discovered in 1930 on the edge of the solar system, although in the early 21st century, it was reclassified as a plutoid instead of a planet proper, leaving eight planets.

Minor-planet moon

moonasteroid moonbinary
Lists of astronomical objects., Lecture at SETI talk (duration 1:00:02). Orbits of Binary Asteroids with Adaptive Optics (Franck Marchis). Satellites and Companions of Minor Planets (CBAT). Asteroids with Satellites Johnston's Archive. The VOBAD database a web page built and designed by F. Marchis and his collaborators (UC-Berkeley/SETI Institute) which contains the parameters of 169 multiple asteroid systems (last update May 9, 2009).


OO 2 molecular oxygen
Earth is unusual among the planets of the Solar System in having such a high concentration of oxygen gas in its atmosphere: Mars (with 0.1% by volume) and Venus have much less. The surrounding those planets is produced solely by the action of ultraviolet radiation on oxygen-containing molecules such as carbon dioxide. The unusually high concentration of oxygen gas on Earth is the result of the oxygen cycle. This biogeochemical cycle describes the movement of oxygen within and between its three main reservoirs on Earth: the atmosphere, the biosphere, and the lithosphere. The main driving factor of the oxygen cycle is photosynthesis, which is responsible for modern Earth's atmosphere.


Neneon gas 21 Ne
Neon's abundance in the universe is about 1 part in 750; in the Sun and presumably in the proto-solar system nebula, about 1 part in 600. The Galileo spacecraft atmospheric entry probe found that even in the upper atmosphere of Jupiter, the abundance of neon is reduced (depleted) by about a factor of 10, to a level of 1 part in 6,000 by mass. This may indicate that even the ice-planetesimals which brought neon into Jupiter from the outer solar system, formed in a region which was too warm to retain the neon atmospheric component (abundances of heavier inert gases on Jupiter are several times that found in the Sun).

Trojan (celestial body)

Trojans in astronomyTrojan asteroidtrojan
In the Solar System, most known trojans share the orbit of Jupiter. They are divided into the Greek camp at (ahead of Jupiter) and the Trojan camp at (trailing Jupiter). More than a million Jupiter trojans larger than one kilometer are thought to exist, of which more than 7,000 are currently catalogued. Only nine Mars trojans, 22 Neptune trojans, two Uranus trojans, and a single Earth trojan, have been found to date. A temporary Venus Trojan is also known. Numerical orbital dynamics stability simulations indicate that Saturn and Uranus probably do not have any primordial trojans.

Discovery and exploration of the Solar System

Solar System explorationexploration of the Solar Systemscientific investigation of the Solar System
In 1966, the Moon became the first Solar System body beyond Earth to be orbited by an artificial satellite (Luna 10), followed by Mars in 1971 (Mariner 9), Venus in 1975 (Venera 9), Jupiter in 1995 (Galileo), the asteroid 433 Eros in 2000 (NEAR Shoemaker), Saturn in 2004 (Cassini–Huygens), and Mercury and Vesta in 2011 (MESSENGER and Dawn respectively). Dawn is orbiting the asteroid–dwarf planet Ceres as of 2015. The first probe to land on another Solar System body was the Soviet Luna 2 probe, which impacted the Moon in 1959.

Interplanetary spaceflight

interplanetaryinterplanetary travelspace travel
In practice, spaceflights of this type are confined to travel between the planets of the Solar System. Remotely guided space probes have flown by all of the planets of the Solar System from Mercury to Neptune, with the New Horizons probe having flown by the dwarf planet Pluto and the Dawn spacecraft currently orbiting the dwarf planet Ceres. The most distant spacecrafts, Voyager 1 and Voyager 2 have left the Solar System as of Dec 8 2018 while Pioneer 10, Pioneer 11, and New Horizons are on course to leave it. In general, planetary orbiters and landers return much more detailed and comprehensive information than fly-by missions.

Timeline of Solar System astronomy

Timeline of Solar System exploration. Timeline of discovery of Solar System planets and their moons. Timeline of Chinese astronomy.

2015 in science

Hubble views of Ganymede’s aurorae suggest the moon, Jupiter's largest, may contain a vast subsurface saline ocean. The U.S. Federal Communications Commission releases the specific details of the net neutrality rules. 17 March – Lava tubes big enough to house entire cities could be structurally stable on the moon, according to a theoretical study presented at the Lunar and Planetary Science Conference. 18 March. NASA reports the detection of an aurora that is not fully understood and an unexplained dust cloud in the atmosphere of the planet Mars.

Standard gravitational parameter

gravitational parametergeocentric gravitational constantheliocentric gravitational constant
For several objects in the Solar System, the value of μ is known to greater accuracy than either G or M. The SI units of the standard gravitational parameter are m 3 s −2. However, units of km 3 s −2 are frequently used in the scientific literature and in spacecraft navigation. The central body in an orbital system can be defined as the one whose mass (M) is much larger than the mass of the orbiting body (m), or M ≫ m. This approximation is standard for planets orbiting the Sun or most moons and greatly simplifies equations.

2014 in science

2014a recent studyearlier findings
China's Yutu rover completes its first examination of the lunar soil. 17 January – NASA reports that a Mars rock, named "Pinnacle Island", that was not in an Opportunity rover image taken on Sol 3528, "mysteriously" appeared 13 days later in a similar image taken on Sol 3540. – UPDATE (14 February 2014): "Mystery" seems to have been solved – the location where the rock was dislodged by the rover has been found. (image). 20 January – The ESA's Rosetta spacecraft "wakes up" from hibernation mode to monitor comet 67P/Churyumov–Gerasimenko for the next 16 months as the comet travels into, and then out of, the inner Solar System.

3rd millennium

New Millenniumthird millenniummillennium
December 3, 2781 – At 06:45 UTC, Venus will occult Neptune. 2791 – Triple conjunction Mars–Jupiter. 2794/95 – Triple conjunction Jupiter–Saturn. The remnants of Comet Ikeya-Seki are expected to return to the inner solar system. It was last seen from Earth in 1965–1966, and broke into three pieces as it approached the Sun. March 25, 2816 – At 15:47 UTC, Mercury will occult Jupiter. March 6, 2817 – At 9:36 UTC, Venus will occult Saturn. April 11, 2818 – At 20:41 UTC, Mercury will occult Mars. February 6, 2825 – At 10:50 UTC, Mars will occult Uranus. 2829/30 – Triple conjunction Mars-Saturn. December 15, 2830 – At 09:40 UTC, Venus will occult Mars. 2842/43 – Triple conjunction Mars-Jupiter.

Satellite system (astronomy)

satellite systemring of satellitessatellite systems
"Jovian system"), or less commonly by the name of their primary (e.g. "Jupiter system"). Where only one satellite is known, or it is a binary orbiting a common centre of gravity, it may be referred to using the hyphenated names of the primary and major satellite (e.g. the "Earth-Moon system"). Many Solar System objects are known to possess satellite systems, though their origin is still unclear. Notable examples include the largest satellite system, the Jovian system, with 79 known moons (including the large Galilean moons) and the Saturnian System with 62 known moons (and the most visible ring system in the Solar System). Both satellite systems are large and diverse.

2019 in science

Astronomers observe the large asteroid Hygiea in higher resolution than ever before, revealing it to be spherical and a likely dwarf planet candidate; possibly the smallest in the Solar System. Researchers report that the interstellar comet 2I/Borisov is outgassing water, and in a manner similar to the outgassing of water in a typical comet in the Solar System.

List of adjectivals and demonyms of astronomical bodies

List of adjectivals and demonyms for astronomical bodies
For instance, for a large portion of names ending in -s, the genitive and therefore the adjective changes the -s to a -d, -t, or -r, as in Isis–Isidian and Ceres–Cererian; This is reflected in Russian and Italian, where both nominal and adjectival forms derive from the genitive: (Italian Erote is avoided for euphemistic reasons; the alternative forms Mima, Meti, Teti, Isi are loans from the French.) However, in other cases the final consonant is not part of the root and so is dropped in Russian and Italian: This approach is not foolproof; note Italian Eros above and Russian Немесида Nemesida (Nemesis), but Italian Nemesi and English adj.

Astrological symbols

astrological symbolastrologysemiquartile
Symbols for the classical planets, zodiac signs, aspects, lots, and the lunar nodes appear in the medieval Byzantine codices in which many ancient horoscopes were preserved. In the original papyri of these Greek horoscopes, there were found a circle with the glyph representing shine for the Sun and a crescent for the Moon. The written symbols for Mercury, Venus, Jupiter, and Saturn have been traced to forms found in late Greek papyri. The symbols for Jupiter and Saturn are identified as monograms of the initial letters of the corresponding Greek names, and the symbol for Mercury is a stylized caduceus. A. S. D.

2012 in science

(PopSci). 2 May – The European Space Agency selects the Jupiter Icy Moon Explorer (JUICE) proposal for its next major space exploration program. The robotic JUICE probe, which is planned to launch in 2022, will conduct in-depth studies of the Jovian moons Callisto, Europa and Ganymede. (BBC). 3 May – In the United Kingdom's first successful ocular implant trial, two men blinded by retinitis pigmentosa have their sight partially restored by prototype microchip implants. (The Telegraph). 8 May – Claire Lomas, a paralyzed British woman, becomes the first person to complete a marathon using a bionic mobility suit. The ReWalk suit allowed her to complete the London Marathon in 16 days.

Impact crater

cratercratersimpact basin
The cratering rate in the inner solar system fluctuates as a consequence of collisions in the asteroid belt that create a family of fragments that are often sent cascading into the inner solar system. Formed in a collision 80 million years ago, the Baptistina family of asteroids is thought to have caused a large spike in the impact rate. Note that the rate of impact cratering in the outer Solar System could be different from the inner Solar System. Although Earth's active surface processes quickly destroy the impact record, about 190 terrestrial impact craters have been identified.