Astronomy Dictionary

ASTRONOMY DICTIONARY

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Words are wonderful and funny things. Every day we hear a word or two that we may not completely understand the meaning of, but we can usually figure it out by the context it is used in. In the world of astronomy, there is a a whole new language to learn, from azimuth to zodical light, and everything in between. Below I hope to shed some light on the meaning of some of the words you may hear, and remember, I am learning too. New words will be added now and then and if there is something you don't find, let me know!


A ALT-AZIMUTH TELESCOPE MOUNT ALTITUDE ANTIMATTER APERTURE APOGEE ARC MINUTE ASTERISM ASTRONOMICAL UNIT (AU) AZIMUTH B BASALT BLACK HOLE BLUE MOON C CASSINI DIVISION CCD CAMERA COLLIMATION CONJUNCTION D DARK MATTER DECLAMATION	E EARTH SHINE ECLIPSE EVENT HORIZON EXOPLANET F FOCAL LENGTH G GALAXY GAMMA RAY BURST (GRB) GREEK ALPHABET GLOBULAR STAR CLUSTERS H HUBBLE SPACE TELESCOPE (HST) I INTERNATIONAL SPACE STATION (ISS) J JET PROPULSION LABORATORY (JPL) K KUIPER BELT OBJECT	L LAIKA LIBRATION LIGHT YEAR LONG PERIOD COMET M MAGNITUDE MESSIER OBJECTS (M OBJECTS) MESSIER, CHARLES N NADIR NASA NEBULA O OCCULTATION OORT CLOUD P PARALLAX PHASES OF THE MOON PLANETARY NEBULA PULSAR	Q QUARK QUASAR R REFLECTING TELESCOPE REFRACTING TELESCOPE S SHORT TERM COMET SPEED OF LIGHT SUN DOG T TELESCOPE TERMINATOR U UNIVERSAL TIME V VARIABLE STAR VIRGO CLUSTER W WHITE DWARF WHITE SUPER GIANT X X-RAY ASTRONOMY Y YELLOW DWARF Z ZODICAL LIGHT

ALT-AZIMUTH TELESCOPE MOUNT -

A "U"-shaped mount that allows a telescope to move both up and down (Altitude) and left to right (Azimuth)

ALTITUDE -

A measurement in mapping astronomical objects on the celestial sphere. An object on the horizon is 0 degrees altitude. An object directly overhead is 90 degrees.

ANTIMATTER -

Matter that is composed of the counterparts of ordinary matter. A particle and its antimatter particle will annihilate when they meet, and energy is released (according to Einstein's E = mc²). Antiparticles have the same mass as their counterpart, but the opposite charge. There seems to be very little antimatter in the universe.

APERTURE -

The aperture is the size of a telescope’s main lens or mirror.

APOGEE -

When an object orbiting the Earth is at its farthest point from Earth, it is at it’s apogee

ARC MINUTE -

A measure which is equal to one-sixtieth of a degree of a circle. A circle has/ 360 degrees.

ASTERISM -

A grouping of stars within a constellation that make another pattern, for example, the big Dipper is a pattern found in the constellation of Ursa Major, the Pleiades is a pattern found in the constellation of Taurus.

ASTRONOMICAL UNIT (AU) -

The distance between the Earth and the Sun which is approximately 92 million miles.

AZIMUTH -

BASALT -

Basalt is a type of igneous rock.

BIG BAN THEORY -

Is a theory that states that the beginning of the universe started as a tiny but powerful explosion of space-time roughly 13.7 billion years ago

BLACK HOLE -

A massive object or region in space that is so dense that its gravity will not let anything escape from it, not even light. Astronomers believe that black holes can be found in the center of each galaxy, including the Milky Way.

BLUE MOON -

The original meaning is when a season, which normally has 3 full moons, has 4 full moons. The third in that season is called a blue moon. A mistake was made in an astronomy magazine in the 1940, accidentally stating that the second full moon in a month is a blue moon, and that definition has stuck!

CASSINI DIVISION -

CCD CAMERA -

COLLIMATION -

CONJUNCTION -

DARK MATTER -

DECLAMATION -

EARTH SHINE -

ECLIPSE -

EVENT HORIZON -

EXOPLANET -

FOCAL LENGTH -

GALAXY -

Stars and other celestial bodies held together by gravitational forces. We live in the Milky Way Galaxy which is a spiral shaped galaxy. There are also elliptical and irregularly shaped galaxies.

GAMMA RAY BURST (GRB) -

GREEK ALPHABET -

GLOBULAR STAR CLUSTERS -

HUBBLE SPACE TELESCOPE (HST) -

INTERNATIONAL SPACE STATION (ISS) -

JET PROPULSION LABORATORY (JPL) -

KUIPER BELT OBJECT -

LAIKA -

LIBRATION -

LIGHT YEAR -

Light travels at 186,000 miles per second. A light year is the distance light travels for one year at this speed. Lets do the math 186,000 miles/second X 60 seconds/minute X 60 minutes/hour X 24 hours/day X 365 days/year = 5,865,696,000,000 miles/year. A light year is 5,865,696,000,000 miles (9,460,800,000,000 kilometers). That's a long way!

LONG PERIOD COMET -

MAGNITUDE -

MESSIER, CHARLES (1730 - 1817) -

A Frenchman who was known as a Comet Ferret. He searched for comets and as he found stationary objects, he would catalogue them. He gave each of the objects numbers, 1 to 110.

MESSIER OBJECTS (M OBJECTS) -

Galaxies, globular clusters, open clusters, nebula, and one pair of double stars, catalogued by Charles Messier between 1758 and 1782, while he was searching for comets. His catalogue is very famous and most amateur astronomers observe all the objects. In March of each year Messier Marathons are held during the new moon weekend. It is in that month, that most or all the M objects can be seen in one night.

NADIR -

NASA -

National Aeronautics and Space Administration. Established on July 29, 1958, by the National Aeronautics Space Act. In addition to the space program, it is also responsible for civilian and and military aerospace research. Since February 2006 NASA's self-described mission statement is to "pioneer the future in space exploration, scientific discovery, and aeronautics research." It's motto is "For the benefit of all." and the motto of NASA's Office of Education is: Shaping the Future: Launching New Endeavors to Inspire the Next Generation of Explorers

NEBULA -