Astronomy Terms

Astronomy terms are used to describe the various phenomena in space. In this section you can learn what every astronomy term means and how it helps us to better understand the cosmos.


Quasar, or Quasi-stellar Object (QSO), a starlike object displaying an unusually large red shift.

Hour, a unit for measuring time, defined as either 1/24 of a day or 3600 seconds (60 minutes).

Hourglass, a device for measuring time. In its usual form it consists of two cone-shaped or oval glass receptacles joined by a narrow neck.

Interferometer, an instrument that uses the interference patterns formed by waves (usually light, radio, or sound waves) to measure certain characteristics of the waves themselves or of materials that reflect, refract, or transmit the waves.

Magnitude, in astronomy, a unit of measurement of the brightness of stars. The scale of magnitude extends from negative numbers (for example, the minus first magnitude) for very bright stars to positive numbers (for example, the fourth magnitude) for dimmer ones.

Meteor. As the term is commonly used, a meteor is a small celestial body that enters the atmosphere of the earth.

Midnight Sun, a name given the sun when it can be seen at midnight during the Arctic or Antarctic summer.

Millennium, in a common Christian belief, the period of 1,000 years before the Last Judgment, during which time Christ and the saints will reign on earth.

Minute, a unit for measuring both time and space. As a unit of time, a minute is 60 seconds, or 1/60 of an hour.

Month, a unit of time. The calendar month is approximately 1/12 of the calendar year.

Nebular Hypothesis, an explanation of how the solar system was formed, proposed by Pierre Simon de Laplace in 1796.