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# Omicron Aquilae

Omicron Aquilae (ο Aql, ο Aquilae) is the Bayer designation for a double star in the equatorial constellation of Aquila. [1]

## Angular distance

In mathematics (in particular geometry and trigonometry) and all natural sciences (e.g. astronomy and geophysics), the angular distance (angular separation, apparent distance, or apparent separation) between two point objects, as viewed from a location different from either of these objects, is the angle of length between the two directions originating from the observer and pointing toward these two objects.

## Apparent magnitude

The apparent magnitude of a celestial object is a number that is a measure of its brightness as seen by an observer on Earth.

## Aquila (constellation)

Aquila is a constellation on the celestial equator.

## Astronomical unit

The astronomical unit (symbol: au, ua, or AU) is a unit of length, roughly the distance from Earth to the Sun.

## Bayer designation

A Bayer designation is a stellar designation in which a specific star is identified by a Greek letter, followed by the genitive form of its parent constellation's Latin name.

## Bortle scale

The Bortle scale is a nine-level numeric scale that measures the night sky's brightness of a particular location.

## Bright Star Catalogue

The Bright Star Catalogue, also known as the Yale Catalogue of Bright Stars or Yale Bright Star Catalogue, is a star catalogue that lists all stars of stellar magnitude 6.5 or brighter, which is roughly every star visible to the naked eye from Earth.

## Celestial equator

The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth.

## Constellation

A constellation is a group of stars that are considered to form imaginary outlines or meaningful patterns on the celestial sphere, typically representing animals, mythological people or gods, mythological creatures, or manufactured devices.

## Double star

In observational astronomy, a double star or visual double is a pair of stars that appear close to each other in the sky as seen from Earth when viewed through an optical telescope.

## Durchmusterung

In astronomy, Durchmusterung or Bonner Durchmusterung (BD), is the comprehensive astrometric star catalogue of the whole sky, compiled by the Bonn Observatory (Germany) from 1859 to 1903.

## Effective temperature

The effective temperature of a body such as a star or planet is the temperature of a black body that would emit the same total amount of electromagnetic radiation.

## F-type main-sequence star

An F-type main-sequence star (F V) is a main-sequence, hydrogen-fusing star of spectral type F and luminosity class V. These stars have from 1.0 to 1.4 times the mass of the Sun and surface temperatures between 6,000 and 7,600 K.Tables VII and VIII.

## Flamsteed designation

A Flamsteed designation is a combination of a number and constellation name that uniquely identifies most naked eye stars in the modern constellations visible from southern England.

## Gliese Catalogue of Nearby Stars

The Gliese Catalogue of Nearby Stars is a modern star catalogue of stars located within 25 parsecs (81.54 ly) of the Earth.

## Henry Draper Catalogue

The Henry Draper Catalogue (HD) is an astronomical star catalogue published between 1918 and 1924, giving spectroscopic classifications for 225,300 stars; it was later expanded by the Henry Draper Extension (HDE), published between 1925 and 1936, which gave classifications for 46,850 more stars, and by the Henry Draper Extension Charts (HDEC), published from 1937 to 1949 in the form of charts, which gave classifications for 86,933 more stars.

## Hipparcos

Hipparcos was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993.

## Minute and second of arc

A minute of arc, arcminute (arcmin), arc minute, or minute arc is a unit of angular measurement equal to of one degree.

## Parallax

Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines.

## Position angle

Position angle, usually abbreviated PA, is the convention for measuring angles on the sky in astronomy.

## Red dwarf

A red dwarf (or M dwarf) is a small and relatively cool star on the main sequence, of M spectral type.

## Smithsonian Astrophysical Observatory Star Catalog

The Smithsonian Astrophysical Observatory Star Catalog is an astrometric star catalogue.

## Star catalogue

A star catalogue (Commonwealth English) or star catalog (American English), is an astronomical catalogue that lists stars.

## Stellar atmosphere

The stellar atmosphere is the outer region of the volume of a star, lying above the stellar core, radiation zone and convection zone.

## Stellar classification

In astronomy, stellar classification is the classification of stars based on their spectral characteristics.

## Stellar rotation

Stellar rotation is the angular motion of a star about its axis.

## Superflare

Superflares are very strong explosions observed on stars with energies up to ten thousand times that of typical solar flares.

## References

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