The corona is visible from Earth during a total solar eclipse. The universe is a large place full of wondrous and unimaginable things. This is the SpellCHEX dictionary for online spell checking. These include eclipsing binaries. Mercury and Venus are the only two inferior planets in our solar system. The temperature cools, which gives the star a reddish appearance. The space within the boundary of the heliopause containing the Sun and the Solar System. A perfect mirror would have an albedo of 100% while a black hole would have an albedo of 0%. ejected the bar patron who started a fight. A very small, white star formed when an average sized star uses up its fuel supply and collapses. This causes the satellite to always keep the same face to the primary. A spectrum is produced when visible light passes through a prism. A partial lunar eclipse occurs when the Moon passes into the penumbra, or partial shadow. More recently, the term has also been used to describe a second full moon in a single month. Stellar Wind Saros Series The temperature at which the motion of all atoms and molecules stops and no heat is given off. In a total lunar eclipse, the Moon passes into the Earth's umbra, or total shadow. Ionosphere Axis ... Ejecta Material from beneath the surface of a body such as a moon or planet that is ejected by an impact such as a meteor and distributed around the surface. The equinoxes occur on or near March 21 and September 22. A type of spiral galaxy which has a small, compact nucleus that is much brighter than the rest of the galaxy. Radiation Belt The theory that suggests the universe is expanding but exists in a constant, unchanging state in the large scale. Orbit Heliopause The square of the period of a planet's orbit is proportional to the cube of that planet's semi major axis; the constant of proportionality is the same for all planets. The larger the blueshift, the faster the object is moving. The center of a black hole, where the curvature of space time is maximal. An interstellar cloud of molecular hydrogen containing trace amounts of other molecules such as carbon monoxide and ammonia. A term used to describe a full moon that occurs during the Moon's closest approach to the Earth. A ray directed from the Sun to a planet sweeps out equal areas in equal times. In 2006, the International Astronomical Union reclassified minor planets as either dwarf planets or small solar system bodies. The amount of matter contained within a given volume. The apparent shift of the celestial poles caused by a gradual wobble of the Earth's axis. Nebulae represent the raw material the stars are made of. Seyfert Galaxy The angular distance of an object in the sky from the celestial equator. On this scale, bright objects have a lower number than dim objects. An increase in temperature caused when incoming solar radiation is passed but outgoing thermal radiation is blocked by the atmosphere. They are highly luminous and presumed to be extragalactic. Patera Main Belt The density of water is 1.0, iron is 7.9, and lead is 11.3. The degree of brightness of a star or other object in the sky according to a scale on which the brightest star has a magnitude -1.4 and the faintest visible star has magnitude 6. Oblateness Satellite Millibar Globular clusters are composed of older stars, and are usually found around the central regions of a galaxy. Also the depression around the opening of a volcano. The saros cycle is equal to 6,585.3 days (18 years 11 days 8 hours). The instrument connected to a telescope that separates the light signals into different frequencies, producing a spectrum. Planemo The North and South poles of the celestial sphere. Scarp The nuclear process whereby several small nuclei are combined to make a larger one whose mass is slightly smaller than the sum of the small ones. Solstice Jupiter and Neptune are examples of major planets. Also known as bolides, fireballs can be several times brighter than the full Moon. The area of partial illumination surrounding the darkest part of a shadow caused by an eclipse. Open Cluster The part of the Sun's atmosphere just above the surface. A term used to describe matter in the universe that cannot be seen, but can be detected by its gravitational effects on other bodies. As the gas spirals in, it becomes hot and emits light or even X-radiation. Broken arc of illuminations seen at the limb of very young or old lunar crescents. Filament The nucleus exhibits variable light intensity and radio emission suggesting that a black hole may be devouring material at the galaxy's center. A planet orbits the Sun in an ellipse with the Sun at one focus. Density is measured in grams per cubic centimeter (or kilograms per liter). Blue Moon A celestial body orbiting the Sun that is massive enough to be rounded by its own gravity but has not cleared its neighboring region of planetesimals and is not a satellite. The surface of the Sun or other celestial body projected against the sky. Sometimes also called quasi-stellar source, this is a star-like object with a large redshift that gives off a strong source of radio waves. The branch of science that explores the chemical interactions between dust and gas interspersed between the stars. Bright patches that are visible on the Sun's surface, or photosphere. Lagrange Point Sidereal Period The range of colors that make up visible white light. In antimatter, protons have a negative charge while electrons have a positive charge. A point in the sky from which meteors in a meteor shower seem to originate. Kelvin Trojan Circumstellar Disk This theory has been abandoned by most astronomers in favor of the big bang theory. Superior Planet Messier Album | The Solar System | The Constellations | Celestial Objects The area around a planet most affected by its magnetic field. Planetesimal The point in the orbit of a planet or other body where it is closest to the Sun. Mare All rights reserved. A meteorite that is composed mainly of iron mixed with smaller amounts of nickel. One bar is equal to 0.987 atmospheres, 1.02 kg/cm2, 100 kilopascal, and 14.5 lbs/square inch. Umbra In reference to a satellite, a prograde orbit means that the satellite orbits the planet in the same direction as the planet's rotation. Declination Photon A system consisting of a spiral galaxy surrounded by several dwarf white galaxies, often ellipticals. Carbon dioxide and water vapor are two of the major gases responsible for this effect. A type of star which is believed to be surrounded by a thin envelope of gas, which is often indicated by bright emission lines in its spectrum. He fired a single shot, then ejected the spent cartridge. A lunar month is equal to 29 days 12 hours 44 minutes. It usually refers to the third full moon in a season with four full moons. Galaxies are found in a variety of sizes and shapes. A star that is near the end of its life cycle where most of its fuel has been used up. The spin of a body about its axis. All of the heavy elements were created in supernova explosions. It usually refers to the third new moon in a season with four new moons. Where: = steel sheet thickness in mm; = laser power in kW (some new laser cutters have laser power of 4 kW); = cutting speed in meters per minute. A giant ball of hot gas that creates and emits its own radiation through nuclear fusion. These are known as pulsars. Also called a binary asteroid. The ring usually contains luminous blue stars. Double Asteroid Jansky Black Hole Mass A shell of gas surrounding a small, white star. Terrestrial Phase The outer edge or border of a planet or other celestial body. Eccentricity This results in a ring of light around the Moon. A large ring of icy, primitive objects beyond the orbit of Neptune. It takes an English sentence and breaks it into words to determine if it is a phrase or a clause. Transit A rotating circumstellar disk of dense gas surrounding a young newly formed star. A stone meteorite that contains no chondrules. Atmosphere Newton's Second Law of Motion Massive clouds of gas in interstellar space composed primarily of hydrogen molecules. This astronomical definition is quite different from the traditional chemistry definition of a metal. A grouping of two stars. Material from beneath the surface of a body such as a moon or planet that is ejected by an impact such as a meteor and distributed around the surface. An expanding shell of gas ejected at high speeds by a supernova explosion. An imaginary sphere around the Earth on which the stars and planets appear to be positioned. Also known as a saros cycle, a period of 223 synodic months that can be used to predict solar and lunar eclipses. A term that means outside of or beyond our own galaxy. Retrograde Orbit Antimatter A form of ionized gas in which the temperature is too high for atoms to exist in their natural state. A small planetary body in orbit around the Sun, larger than a meteoroid but smaller than a planet. The apparent change in wavelength of sound or light emitted by an object in relation to an observer's position. Yellow Dwarf Debris disks can be created as the next phase in planetary system development following the protoplanetary disk phase. A state that occurs when compression due to gravity is balanced by a pressure gradient which creates a pressure gradient force in the opposite direction. A star that fluctuates in brightness. An extremely bright meteor. Interplanetary Magnetic Field To cause a planet or satellite to deviate from a theoretically regular orbital motion. The area of total darkness in the shadow caused by an eclipse. A tight concentration of stars and gas found at the innermost regions of a galaxy. Where horizons or other properties are intermittent or cyclic over an interval of 2 to 7 m, the pedon includes one-half of the cycle (1 to 3.5 m). Astrochemistry The further South you go the fewer stars will be circumpolar. A term used to describe an exceptionally bright meteor. A dictionary file. Roche Limit A point directly overhead from an observer. This information should not be considered complete, up to date, and is not intended to be used in place of a visit, consultation, or advice of a legal, medical, or any other professional. The apparent change in shape of the Moon and inferior planets as seen from Earth as they move in their orbits. A term used since the 19th century to describe objects, such as asteroids, that are in orbit around the Sun but are not planets or comets. Solar Wind A name given to a planet composed mainly of rock and iron, similar to that of Earth. The Doppler effect can be used to estimate an object's speed and direction. A distinctive area of broken terrain. Event Horizon Blueshift It has to have sufficient mass to overcome rigid body forces and achieve hydrostatic equilibrium. A planet at opposition is at its closest approach to the Earth and is best suitable for observing. A total solar eclipse occurs when the Moon is close enough to completely block the Sun's light. Mercure est la planète la plus proche du Soleil et la moins massive du Système solaire [N 1].Son éloignement au Soleil est compris entre 0,31 et 0,47 unité astronomique (soit 46 et 70 millions de kilomètres), ce qui correspond à une excentricité orbitale de 0,2 — plus de douze fois supérieure à celle de la Terre, et de loin la plus élevée pour une planète du Système solaire. Tidal Heating Focus Areas are a way of grouping NASA interests and related technologies with the intent of making it easier for proposers to understand related needs across the Agency and thus identify subtopics where their research and development capabilities may be a good match. Obliquity Meteors become meteorites if they reach the ground. Coma It is merely a coinsidence in timing caused by the fact that the lunar month is slightly shorter than a calendar month. Bar 中文的月為象形文字，在甲骨文中月像一彎眉月的樣子。 東漢 許慎在《說文解字》一書中分析月的字型時說：月，闕也。 人們經過觀察，發現月圓的時間少，闕（弦月或眉月等）的時間多，於是就照眉月的樣子創造出這個象形字。 在英語中月的專有名稱是「 the Moon 」 。 The movement of an object either towards or away from a stationary observer. The interval of a complete lunar cycle, between one new Moon and the next. Celestial Poles A term used to describe an extra new that occurs in a season. A spacecraft in geosynchronous orbit appears to hang motionless above one position of a planet's surface. A large grouping of stars. Irregular satellites are believed to have been captured by the planet's gravity rather than being formed along with the planet. The outer part of the Sun's atmosphere. A compressed core of an exploded star made up almost entirely of neutrons. This name derives from a generalization of the names of some of the largest asteroids in Jupiter's Lagrange points. This grouping can be apparent, where the stars seem close together, or physical, such as a binary system. The angular distance of a planetary body from the Sun as seen from Earth. Some can even be accompanied by a sonic boom. Kepler's First Law Supermoon A torus or ring-shaped accumulation of gas, dust, or other debris in orbit around a star in different phases of its life cycle. The gravitational pull is so strong that not even light can escape. The collapsed core of a massive star. An event where a large number of meteors enter the Earth's atmosphere from the same direction in space at nearly the same time. The bright visible surface of the Sun. Kirkwood Gaps The angle between a body's equatorial plane and orbital plane. Prograde Orbit Evolved Star The speed required for an object to escape the gravitational pull of a planet or other body. Opposition Neutrino Circumpolar Star A temperature scale used in sciences such as astronomy to measure extremely cold temperatures. Eclipsing Binary A binary system where one object passes in front of the other, cutting off some or all of its light. X-ray Wavelengths of electromagnetic radiation that are visible to the human eye. A bowl-shaped depression formed by the impact of an asteroid or meteoroid. ° In assessment of scatter around Jupiter and bright stars, straight-through observing without any diagonal was very clearly and distinctively better, perhaps showing only half as much scatter as the best diagonal. Hubble's Law Space Exploration | Space Games | Space Gallery | Space Links, Visit Us on Facebook | Follow Us on Twitter. Double Star Shell Star Perihelion Cosmic Ray Known as the Aurora Borealis in the northern hemisphere. A large distance often used in astronomy. The cloud of dust and gas out of which the Solar System was believed to have formed about 5 billion years ago. Also known as the poles, this is an imaginary line through the center of rotation of an object. The average period of revolution of the Moon around the Earth in reference to a fixed star, equal to 27 days, 7 hours, 43 minutes in units of mean solar time.