Space Terms

Arc minute is an important unit in astronomy since it is an expression that communicates small angles. It is also called minute of arc or minute of angle (MOA), and is a unit of measurement for angles. An arc minute is equal to one sixtieth of a degree, and because one degree is composed of […]

Archeoastronomy is the study of ancient ways of understanding astronomical phenomena. It inquires in how people of the past ages made sense of celestial events, how they interpreted then and how the sky figured in their daily lives.

In astronomical parlance, apparition is the term that refers to the appearance of periodic comets. Periodic comets are classified as those comets whose orbital period does not reach 200 years, or those who have been seen in more than one perihelion passage. They are also called short-period comets. The term periodic comet is also used

Apparent magnitude is the degree of brightness of a celestial body as observed on Earth, compared to its actual brightness marked by the atmospheric absence. The brighter the object projects to us, the lower its magnitude.

The point in an elliptical orbit said to be at which a satellite is at its furthest from the Earth is referred to as apogee. Whenever a satellite is at its apogee, its travel around the body is also at its slowest. The origin of the name alone is enough to dictate such meaning. Apo

Apochromat, or APO, is the simplified term used to refer to apochromatic lens, a photographic or other lens that has the capability to correct spherical and chromatic aberration better than the usual achromat lenses.

Anaglyph was first introduced in 1853 by Wilhelm Rollman in Leipzig, Germany. It was the first historical 3D stereoscopic visualization made from red/blue or red/green glasses.

Accretion disk results when matter, such as gas, from a stellar body spirals toward another central body due to gravity. To more clearly understand the phenomenon, take two bodies orbiting each other – in this case, take a very dense neutron star and a medium-sized yellow star like our sun. Through gravitational effects, some gaseous

Modern sensing techniques have detected that in some galaxies, the center emits so much radiation that it produces more light that the rest of the galaxy. The high-activity center is called an active galactic nuclei or AGN. Galaxies hosting an AGN is named an active galaxy. The extreme emission of electromagnetic radiation of active galaxies

Adaptive optics is a technique employed that allow ground-based telescopes to adjust for the blurring effects of the Earth’s atmosphere. These distortions are called wave front errors. When light from a star enters the Earth’s atmosphere, it gets distorted by a variety of factors such as temperature differences between the atmosphere’s layers, wind and many