Astronomy Glossary of Key Terms

"I don't think the human race will survive the next thousand years unless we spread into space." — Stephen Hawking

Scientific VocabularyThis refers to the words used by scientists to accurately describe matter, organisms, processes and systems. These words have an exact meaning or definition, and application. Sometimes these words are used incorrectly or imprecisely when applied in everyday use.Because Science is dynamic -characterized by constant change, activity, or progress, you may find that sometimes the definitions for science vocabulary will change and develop as scientists continue to understand the universe by incorporating new ideas, thinking and experimental evidence.

It’s important to have the correct most up to date definitions of science vocabulary.

“It’s been exactly one whole year since I saw you last, 12 Months!”

“I know! Scientifically speaking, the Earth has only made one revolution around the sun, the moon has orbited the earth about 12 times since I saw you last! And the Earth has rotated on it’s axis 365 and ¼ times! How have you been?”

We don’t normally speak scientifically! A glossary of key terms will help you to develop your ‘Science Vocab’ to enable you to develop your Science Knowledge and understanding… mostly just so you know what we are talking about.

Astronomy The branch of science that deals with celestial objects, space,

and the physical universe as a whole.

Astronomy was greatly furthered by the invention of the telescope. From the Greek word astronomos meaning ‘star-arranging.’

Milky Way Galaxy (northern band) many bright stars, dark dust lanes, red emission nebulae, blue reflection nebulae and star clusters can be seen. Astronomy Picture of the Day, John P. Gleeson July 10, 2011http://apod.nasa.gov/apod/archivepix.html

Celestial Positioned in or relating to the sky, or outer space as observed

in astronomy: a celestial body.

Astrology The study of the movements and relative positions of celestial bodies

interpreted as having an influence on human affairs and the natural world.Ancient observers of the heavens developed elaborate systems of explanation

based on the movements of the sun, moon, and planets through the constellations of the zodiac, for predicting events and for casting horoscopes. By 1700 astrology had lost intellectual credibility in the West, but continued to have popular appeal.

Modern astrology is based on that of the Greeks.

Constellationa group of stars forming a recognizable pattern that is traditionally

named after its apparent form or identified with a mythological figure. Modern astronomers divide the sky into eighty-eight constellations with

defined boundaries

Zodiaca belt or ring of constellations that lines the ecliptic (the apparent path

of the sun, the path of the moon and planets roughly lie within the ecliptic also) It is divided into twelve equal signs (Aries, Taurus, Gemini,

Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, Pisces).

Horoscopeforecast of a person's future, typically including a delineation of

character and circumstances, based on the relative positions of the stars and planets at the time of that person's birth.

• a short forecast for people born under a particular sign, esp. as published in a newspaper or magazine.

AstronomerAn expert in or a student of astronomy.

GravityThe force that attracts a body toward the center of the earth,

or toward any other physical body having mass.

MassThe quantity of matter that a body contains.

Mass and weight are not the same. In science these words have special meanings. Mass is a measure of the amount of matter (material) in an

object and is commonly measured in grams (g) or kilograms (kg).

WeightThe force acting on the mass of a body by a gravitational field.Weight and mass are not the same. Weight is a measure of the force of

gravity pulling on a mass and is measured in newtons (N). Under ordinary conditions the mass of an object can be said to be constant (the object’s

mass will be the same at different locations in the Universe). The weight of an object is not constant, since the force of gravity varies from place to place

DayA single rotation of a planet

YearThe time taken by a planet to make one revolution around the

sun.

Lunar MonthA month measured between successive new moons (roughly

291/2 days).The earth’s moon orbits the earth in a period of 29.5 days. There are

different phases of the moon illuminated during its orbit. .

Phases of the moon

Lunar phase is the appearance of the illuminated (lighted) portion of the Moon as seen by an observer, usually on Earth.

• The lunar phases changes as the Moon orbits the Earth, according to the positions of the Earth, Moon, and Sun.

•One half of the lunar surface is always illuminated by the Sun (except during lunar eclipses), and is bright, but…

• the portion that is visible to an observer can vary from 100% (full moon) to 0% (new moon).

EclipseAn obscuring of the light from one celestial body by the passage of another between it and the observer or between it and its source of

illumination.E.g. Lunar eclipse: an eclipse in which the moon appears darkened as it passes

into the earth's shadow.E.g. Solar eclipse: an eclipse in which the sun is obscured by the moon.

Lunar Eclipse time lapse video (39sec)http://www.youtube.com/watch?v=Xuej7_orvfM&feature=relatedTotal solar eclipse (2min) http://www.youtube.com/watch?v=XMyqPxFh5Zw

MoonThe natural satellite of the earth, visible (chiefly at night) by reflected light from the sun. A natural satellite of any planet.

The earth's moon orbits the earth in a period of 29.5 days, going through a series of phases from new moon to full moon. A natural satellite or moon is a celestial body that orbits a planet or smaller

body, which is called its primary.

Artificial SatellitesAn artificial body placed in orbit around the earth or moon or

another planet in order to collect information or for communication.

PlanetThe definition of planet set in 2006 by the

International Astronomical Union (IAU) states that in the Solar System a planet is a celestial body that: is in orbit around the Sun,

has sufficient mass to assume hydrostatic equilibrium (a nearly round shape), and has "cleared the neighbourhood" around its orbit.

SunThe star around which the earth orbits. The sun is the central

body of the solar system. It provides the light and energy that sustains life on earth, and its position relative to the earth's axis determines the

terrestrial seasons.

Solar SystemThe collection of eight planets and their moons in orbit around

the sun, together with smaller bodies in the form of 5 dwarf planets, small solar system bodies (SSSB), asteroids,

meteoroids, and comets.

Galaxy A system of millions or billions of stars, and stellar remnants, an interstellar medium (between stars) of gas and dust and an

important but poorly understood component tentatively dubbed dark matter, held together by gravitational attraction.

The Milky way is the galaxy of which the solar system is a part; is located is a disk-shaped spiral galaxy with approximately 100,000

million stars.

UniverseAll existing matter and space considered as a whole; the

cosmos. The universe is believed to be at least 10 billion light years in diameter and contains a vast number of galaxies; it has been expanding since its

creation in the big bang about 13 billion years ago.

TelescopeAn instrument designed to make distant objects appear nearer, containing an arrangement of lenses, or of curved mirrors and lenses, by which rays of light (electromagnetic radiation) are

collected and focused and the resulting image magnified.

Space ProbeAn unmanned exploratory spacecraft designed to transmit

information about its environment.

AsteroidA small rocky body (SSSB) orbiting the sun.

Large numbers of these, ranging in size from nearly 1,000 km across to dust particles, are found esp. between the orbits of Mars and Jupiter

and a few pass close to the earth or enter the atmosphere as meteors.

253 MathildeThe 253rd asteroid to be discovered, measuring about 50km across. Photo taken 1997 by NEAR Shoemaker probe.

CometA celestial object consisting of a nucleus of ice and dust and, when

near the sun, a “tail” of gas and dust particles pointing away from the sun.

Comet-Hale-Bopp-29-03-1997

MeteorA small body of matter from outer space that enters the

earth's atmosphere, becoming incandescent -emitting light as a result of being heated as a result of friction and appearing as

a streak of light.

Black HoleA region of space having a gravitational field so intense that no

matter or radiation can escape. Probably formed when a massive star exhausts its nuclear fuel and collapses under its own gravity.