Science Astrnomy Definitions

A scientist who studies Astronomy

• A Celestial Object is any object that exists in space.

Revolution is the time it takes for an object to orbit another object.

The turning of an object around an imaginary axis running through it.

A constellation is a group of stars that seem to form a distinctive pattern in the sky.

Apparent Magnitude is the brightness of a star as seen from Earth.

The location above or below the Equator.

The distance that light travels in one year. About 9.5*10¹² km.

The Rising and falling of ocean waters caused by the Moon's and Earth's gravity.

The phenomenon in which one celestial object moves directly in front of another celestial object.

The monthly progression of changes in the appearance of the Moon that result from different portions of the Moon's sunlit side being visible from Earth.

An ellipse is a curve that is generally referred to as being oval or the shape of an egg.

A lunar eclipse is the phenomenon in which the full Moon passes into Earth's shadow.

• The phenomenon in which the shadow of the Moon falls on Earth's surface.

An astronomical unit is the average distance between the Earth and Sun.

Orbital radius is the average distance between the Sun and an object that's orbiting the Sun.

A planet is an object that orbits one or more stars (and is not a star itself), is spherical, and doesn't share its orbit with another object.

Retrograde motion is the movement of an object in the sky, usually a planet, from eat to west, rather than its normal motion from west to east; this effect is generally produced when Earth is passing the planet in its orbit.

a Solar System is a group of planets that circle one or more stars.

An asteroid is an object in space that ranges in size from a tiny speck, like a grain of sand, to 500 km wide; most asteroids originate in the asteroid belt between Mars and Jupiter.

A comet is an object composed of rocky material, ice, and gas; comes from the Kuiper Belt or Oort Cloud.

A meteoroid is a piece of rock moving through space.

A meteor is a meteoroid that hits Earth's atmosphere and burns up.

A meteorite is a meteoroid that is large that is large enough to pass through Earth's atmosphere and reach the ground, without being totally burned up.

Radiation consisting of electromagnetic waves, including radio waves, infrared, visible light, ultraviolet, x-rays, and gamma rays travelling at the speed of light.

A telescope that uses mirrors to collect the light from an object.

A telescope that uses a lens to collect the light from an object.

An artificial (human-made) object that orbits Earth, the Moon, or other celestial bodies; also a celestial body that orbits another body of larger size.

The theory that describes how stars and planets form from contracting, spinning disks of gas and dust.

Also called diffuse nebula. A cloud of interstellar gas and dust.

An area of strong magnetic fields on the Sun's photosphere. (Black dots) Periodically visible due to our revolution of the Sun and the Sun's rotation.

A stream of fast-moving charged particles ejected by the Sun into the solar system.

An optical instrument that produces a spectrum from a narrow beam of light, and usually projects the spectrum onto a photographic plate or a digital detector.

Certain specific wavelengths within a spectrum characterized by lines; spectral lines identify specific chemical elements.

The graph showing the absolute magnitude plotted against the surface temperature for a group of stars.

A hot, condensed object at the centre of a nebula.

The process of energy production in which hydrogen nuclei combine to form helium nuclei.

The Sun's surface.

A star's total energy output per second; its power in joules per second (J/s)

The magnitude of a star that we would observe if the star were 32.6 light-years from Earth.

The galaxy that includes our solar system; appears as a hazy-white band in the night sky.

A huge collection of stars, planets, dust and gas that is held together by gravity.

A collection of stars held together by gravity.

A collection of 50-100 stars; open clusters appear along the main band of the milky way.

A collection of 100'000 to a million stars that is arranged in a distinctive spherical shape; globular clusters are around the centre of the milky way.

The small group of 40 galaxies that includes the milky way.

A giant cluster of 4-25 galaxies that is hundreds of millions of light-years in size.

The study of the Universe

The change in pitch of sound due to the motion of the source relative to an observer; also, the change in frequency of light source due to its motion relative to an observer.

The effect in which objects moving away from an observer have their wavelengths lengthened, toward the red end of the visible spectrum.

The radiation left over from the Big Bang, which fills the Universe.

The effect in which objects moving toward an observer have their wavelengths shortened, toward the blue end of the visible spectrum.

The event that may have triggered the expansion of the Universe 14 billion years ago.