Astronomy and related astronomical terms

The astronomical field that deals with objects beyond the Milky Way; especially, galaxies and quasars.

A region in the sun's photosphere brighter than its surroundings, related to sunspots and to the sun's magnetic field.

Such regions are at a higher temperature than the surrounding areas.

A popular term for a meteor.

The point at which the sun, traveling from south to north on the ecliptic, crosses the celestial equator.

Identical to the vernal equinox.

A sudden, transitory burst of activity in the sun's atmosphere involving the release of radiation and high-energy particles.

The origin of flares is uncertain, although they seem to be related to areas of high magnetic field.

A star whose brightness can increase by as much as two to 100 times in a matter of minutes, then return to normal.

A flying object whose nature is unknown; especially, anything considered to have extraterrestrial origins.

The breakup of a gas cloud into discrete regions as a result of the gravitational collapse of denser regions in the gas or inhomogeneities (something that is not homogeneous or uniform).

The number of repetitions or cycles per unit time of a complete waveform, expressed in Hertz (Hz).

Shortwaves pass the point at high frequencies, longer ones at low frequencies.

The study of the Milky Way galaxy and all its contents.

This is in contrast to extragalactic astronomy, which is the study of everything outside our galaxy, including all other galaxies.

1. A congregation, or large grouping, of millions or billions of stars, held together by gravity or gravitational attraction and also known as an "island universe".
2. A collection of dust, gas, and stars measuring thousands of parsecs across.

A parsec comes from PARallax + SECond which is a unit of distance between stars. One parsec is about 3 1/4 light years.

The four satellites of Jupiter first observed by Galileo Galilei; namely, Io, Europa, Ganymede, and Callisto.

An Italian astronomer (1564-1642) and physicist associated with many of the important advances in science in the late Middle Ages.

Galileo made major investigations in the fields of mechanics, including experiments on acceleration, friction, inertia, and falling bodies.

He is credited with improving the telescope and pioneered its use for astronomical observations, discovdering mountains on the moon, many new stars, the four satellites of Jupiter, and the composition of the Milky Way.

He also supported the theories of Copernicus concerning the motions of the planets.

Electromagnetic radiation with wavelengths shorter than those of X-rays.

The planets Jupiter, Saturn, Uranus, and Neptune.