Glossar - D

Debris disk is a ring-shaped circumstellar disk of dust and debris orbiting its host star. It is created by collisions between planetesimals. A debris disk can be discerned from an infrared excess being emitted from the star system, as the orbiting debris re-radiates the star's energy into space as heat.

Declination, in the equatorial coordinate system, is the celestial equivalent of terrestrial latitude. Coordinates north of the celestial equator are measured in positive degrees from 0° to 90°, while coordinates to the south use coordinates in negative degrees.

Decretion disk is a circumstellar disk formed from gas ejected from the central star that now follows a near Keplerian orbit around it. This type of disk can be found around many Be stars.[5]

Double star is a pair of stars that appear near each other on the celestial sphere. This can happen because, by chance, the pair lie along nearly the same line of sight from the Earth. If the two are located in physical proximity to each other, they may form a co-moving pair or a binary star system.

Dwarf star is the category of ordinary main sequence stars like the Sun, in contrast to evolved giant stars like Betelgeuse and Antares. Confusingly, the term dwarf has also came to include stellar remnants known as white dwarfs plus low mass, sub-stellar objects called brown dwarfs.