| lowell, percival 1855-1916. | American astronomer. he founded the lowell observatory in arizona (1894), where his studies of mars led him to believe that the linear markings (first noted by schiaparelli) on the surface were "c... |
| lumiere zodicale | A faint glow from light scattered off of interplanetary dust along the plane of the ecliptic. |
| macula | Dark spot. |
| magnetotail | The portion of a planetary magnetosphere which is pushed in the direction of the solar wind. |
| magnitude | The degree of brightness of a celestial body designated on a numerical scale, on which the brightest star has magnitude -1.4 and the faintest visible star has magnitude 6, with the scale rule such... |
| mare | Literally "sea" (a very bad misnomer, still in use for historical reasons); really a large circular plain |
| mensa | Mesa, flat-topped elevation. |
| metal | Used by astrophysicists to refer to all elements except hydrogen and helium, as in: "the universe is composed of hydrogen, helium and traces of metals". |
| meteorite | A rock of extra-terrestrial origin found on earth |
| meteoroid | A small rocky object orbiting the sun; smaller than an asteroid |
| millibar | 1/1000 of a bar. standard sea-level pressure is about 1013 millibars. |
| minor planets | The official term used for asteroids. |
| mons | Mountain (plural: montes) |
| neujmin, grigoriy n. | Ukrainian astronomer; discovered the asteroid 951 gaspra. |
| neutrino | A fundamental particle supposedly produced in massive numbers by the nuclear reactions in stars. they are very hard to detect since the vast majority of them pass completely through the earth with... |
| newton, isaac 1642-1727 | English cleric and scientist; discovered the classical laws of motion and gravity; the bit with the apple is probably apocryphal. (10k jpg) |
| nicholson, seth barnes 1891-1963 | American astronomer; discovered lysithea, ananke, carme and sinope; also did important work on sunspots. |
| oceanus | Literally "ocean"; really a large circular plain |
| old | A planetary surface that has been modified little since its formation typically featuring large numbers of impact craters (compare young). |
| oort, jan hendrik 1900-1992 | Dutch astronomer made major contributions to knowledge of the structure and rotation of our galaxy. more or less as a sideline, oort studied comets as well. the result of this work was a theory, n... |
| ovoid | Shaped like an egg |
| palus | Literally "swamp"; really a small plain |
| parsec | = 206265 au = 3.26 light year |
| patera | Shallow crater; scalloped, complex edge. |
| penumbra | Literally, "dim light"; the outer filamentary region of a sunspot. |
| perihelion | The point in its orbit where a planet is closest to the sun. when refering to objects orbiting the earth the term perigee is used; the term periapsis is used for orbits around other bodies. (oppos... |
| perrine, charles dillon 1867-1951 | Argentine-american astronomer who discovered himalia and elara. |
| perturb | To cause a planet or satellite to deviate from a theoretically regular orbital motion . |
| photosphere | The visible surface of the sun; sunspots and faculae are observed in the photosphere. |
| plage | Bright regions seen in the solar chromosphere. плывун; |
| planitia | Low plain. |
| planum | Plateau or high plain. |
| pope, alexander 1688-1744 | English writer best remembered for his satirical mock-epic poems the rape of the lock and the dunciad. |
| prominence | A strand of relatively cool gas in the solar corona which appears bright when seen at the edge of the sun against the blackness of space. |
| promontorium | Cape; headland |
| ptolemy 87-150 | (aka claudius ptolemaeus) alexandrian astronomer, mathematician, and geographer who based his astronomy on the belief that all heavenly bodies revolve around the earth. (10k gif; more) |
| red giant | A star that has low surface temperature and a diameter that is large relative to the sun. |
| regio | Region. |
| resolution | The amount of small detail visible in an image; low resolution shows only large features, high resolution shows many small details |
| resonance | A state in which one orbiting object is subject to periodic gravitational perturbations by another. |
| reticulum | Reticular (net-like) pattern |
| rima | Fissure. |
| roche limit | The closest a fluid body can orbit to its primary without being pulled apart by tidal forces. a solid body may survive within the roche limit if the tidal forces do not exceed its structural stren... |
| rupes | Scarp. |
| scarp | Line of cliffs produced by faulting or erosion. |
| scopulus | Lobate or irregular scarp. |
| semimajor axis | The semimajor axis of an ellipse (e.g. a planetary orbit) is 1/2 the length of the major axis which is a segment of a line passing thru the foci of the ellipse with endpoints on the ellipse itself... |
| shakespeare, william 1564-1616 | English playwright and poet; wrote some good skits. |
| sidereal | Of, relating to, or concerned with the stars. sidereal rotation is that measured with respect to the stars rather than with respect to the sun or the primary of a satellite. |
| silicate | A compound containing silicon and oxygen (e.g. olivine) |
| sinus | Literally "bay"; really a small plain |
| solar cycle | The approximately 11-year quasi-periodic variation in frequency or number of solar active events. |
| solar nebula | The cloud of gas and dust that began to collapse about 5 billion years ago to form the solar system. |
| solar wind | A tenuous flow of gas and energetic charged particles, mostly protons and electrons -- plasma -- which stream from the sun; typical solar wind velocities are near 350 kilometers per second. |
| spicules | Grass-like patterns of gas seen in the solar atmosphere. |
| stellar classification | Stars given a designation consisting of a letter and a number according to the nature of their spectral lines which corresponds roughly to surface temperature. the classes are: o, b, a, f, g, k, a... |
| sublime (or sublimate) | To change directly from a solid to a gas without becoming liquid |
| sulcus | Subparallel furrows and ridges. |
| sunspot | An area seen as a dark spot on the photosphere of the sun; sunspots are concentrations of magnetic flux, typically occurring in bipolar clusters or groups; they appear dark because they are cooler... |
| terra | Extensive land mass. |
| tessera | Tile; terrain formed of polygonal pattern |
| tholus | Small domical mountain or hill. |
| thomson, william 1824-1907 | Aka lord kelvin, british physicist who developed the kelvin scale of temperature. also supervised the laying of a trans-atlantic cable. (10k gif) |
| tombaugh, clyde 1906-1997 | American astronomer; discovered pluto. (more, more, 4k gif) |
| trekkie | (also "trekker") a devotee of the science fiction program star trek. |
| umbra | The dark central region of a sunspot. |
| unite astronomique (ua) | = 149,597,870 km; the average distance from the earth to the sun. 1 au is a long way -- at 100 miles per hour (160 kph) it would take over 100 years to go 1 au. |
| vallis | Sinuous valley (plural: valles) |
| vastitas | Widespread lowlands. |
| verne, jules 1828-1905 | French writer who is considered the founder of modern science fiction. his novels include "journey to the center of the earth" and "from the earth to the moon". |
| volatile | As a noun, this refers to substances that are gases at ordinary temperatures. in astronomy it includes hydrogen, helium, water, ammonia, carbon dioxide and methane. |
| white dwarf | A whitish star of high surface temperature and low intrinsic brightness with a mass approximately equal to that of a sun but with a density many times larger. |
