Astronomy DSST

Quasar

Short for "quasi-stellar radio source," a bright, point-like object that produces the luminosity of 100 to 1,000 galaxies within a region the size of a solar system.

Pulsar

A rapidly rotating neutron star which emits radiation in magnetic pulses.

Redshift

A shift in the lines of an object's spectrum toward the red end. It indicates that an object is moving away from the observer. The larger it is, the faster the object is moving.

Asterism

A cluster of stars (or a small constellation).

Equinox

Either of the two celestial points at which the celestial equator intersects the ecliptic plane.

Ecliptic Plane

the plane of the Earth's orbit around the Sun.

Brown Dwarf

"Failed" star; a star not massive enough to sustain nuclear fusion.

Calderas

Depressions that form when a volcano collapses, as opposed to craters formed by meteoroid impact.

Red Giant

A star that expands and cools once it runs out of hydrogen fuel.

White Dwarf

Stage in which a star has used up its helium and its outer layers escape into space, leaving behind a hot, dense core that contracts.

Galactic Bulge

Also called nuclear bulge, this is a swelling at the center of spiral galaxies. Bulges consist of old stars and extend out a few thousand light-years from the galactic centers.

Neutron Star

The small, dense remains of a high-mass star after a supernova.

Radio Galaxy

Very bright, often giant, elliptical galaxy type that emits as much or more energy in the form of radio wavelengths as it does wavelengths of visible light.

Seyfert Galaxy

Type of active galaxy whose emissions come from a very small region within the nucleus of an otherwise normal-looking spiral system.

Radiation

Energy that is radiated or transmitted in the form of rays or waves or particles.

Electromagnetic Spectrum

Arrangement of electromagnetic radiation--including radio waves, visible light, gamma rays, X-rays, ultraviolet waves, infrared waves, and microwaves--according to their wavelengths.

Comet

A relatively small extraterrestrial body consisting of a frozen mass that travels around the Sun in a highly elliptical orbit.

Binary Star

A pair of stars held together by their mutual gravity and in orbit about each other which can be seen with a telescope as separate objects.

Solstice

Either of the two times of the year when the Sun is at its greatest distance from the celestial equator.

Sunspots

Areas on the sun's surface that are cooler and less bright than surrounding areas, are caused by the sun's magnetic field, and occur in cycles.

Lunar Month

The period between successive new moons (29.531 days).

Galileo Galilei

Italian astronomer and mathematician who was the first to use a telescope to study the stars.

Nicolaus Copernicus

Polish astronomer who produced a workable heliocentric model of the solar system.

Nebula

An immense cloud of gas (mainly hydrogen) and dust in interstellar space.

Retrograde

An orbit that is backward or contrary to the orbital direction of the other planets.

Parallax

The apparent displacement of an object as seen from two different points that are not on a line with the object.

Newton's Laws

1. If no forces act on a body, its speed and direction of motion stay constant (an object in motion stays in motion, an object at rest stays at rest).

2. Force=mass x acceleration (F=ma).

3. When two bodies interact, they exert equal and opposite forces on each other.

Emission Line

A narrow, bright region of the spectrum, produced when electrons in atoms jump from one energy level to a lower energy level.

Population I Stars

The younger stars, some of which are blue, that populate a galaxy's disk, especially its spiral arms. High in heavy metals.

Population II Stars

The older, redder stars that populate a galaxy's hale and bulge. Low metallicity.

Jovian Planets

The large, outer planets made of gas - Jupiter, Saturn, Uranus, & Neptune. These all have large moons and rings.

Terrestrial Planets

The name given to the four inner planets: Mercury, Venus, Earth, and Mars. Mercury and Venus lack moons.

Globular Clusters

Large, dense groupings of older stars held together by mutual gravitational attraction, which is what keeps them together longer than open clusters.

Meteor

A streak of light in the night sky that results when a meteoroid hits the earth's atmosphere, and air friction causes the meteoroid to melt or vaporize or explode.

Orion-Cygnus Arm

The portion of the Milky Way in which our solar system resides.

Light Year

The distance that light travels in one year; about 9.46 trillion kilometers.

Doppler Effect

A change in the apparent frequency of a wave, as observer and source move toward or away from each other.

23:56

The most precise measurement of Earth's rotation time.

Blue Giant

Large, hot, bright star late in the main sequence, having exhausted its hydrogen fuel. Its name comes from its color and size.

Cepheid Variable

A type of pulsating variable star that changes brightness in a regular and predicable manner, making it a useful "standard candle" for learning absolute magnitudes.

Absorption Lines

The dark lines in a spectrum where light of particular wavelengths has been absorbed.

300,000,000

The speed of light in meters per second. It is also 300,000 kilometers per second and 186,000 miles per second.