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Å

Å   Quick reference

A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

Symbol for *angstrom.

A-OK

A-OK   Quick reference

A Dictionary of Space Exploration (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

‘Very OK’ or ‘Great’. John ‘Shorty’ Powers, NASA's public-relations officer, introduced the term by misquoting astronaut Alan *Shepard during the first sub-orbital flight in ...

A-type asteroid

A-type asteroid   Quick reference

A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

A rare type of asteroid that has both a moderately high albedo (0.13–0.35) and an extremely reddish spectrum at wavelengths shorter than 0.7 ...

A-type rocket

A-type rocket   Quick reference

A Dictionary of Space Exploration (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

A name used in the West for a series of Soviet rocket boosters. The A-1 launched *Sputnik and the cosmonaut ...

AAO

AAO   Quick reference

A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

Abbr. for *Australian Astronomical Observatory.

AAS

AAS  

Abbreviation for either American Astronautical Society or American Astronomical Society.
AAS

AAS   Quick reference

A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

Abbr. for *American Astronomical Society.

AAT

AAT   Quick reference

A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

Abbr. for *Anglo-Australian Telescope.

AAVSO

AAVSO   Quick reference

A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

Abbr. for *American Association of Variable Star Observers.

A band

A band   Quick reference

A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018
A broad *Fraunhofer line in the Sun’s spectrum at around 759 nm, due to absorption by oxygen in the Earth’s atmosphere. Because the oxygen is in molecular form, the A band is actually a ... More
Abbé Georges Édouard Lemaître

Abbé Georges Édouard Lemaître  

(1894–1966) Belgian astronomer and cosmologistLemaître was born at Charleroi in Belgium. After serving in World War I, he studied at the University of Louvain in Belgium from where he graduated in ...
Abd al-Ramān al-Ṣūfī

Abd al-Ramān al-Ṣūfī  

(903–86)Arabastronomer (Latinized name Azophi), born in modern Iran. His Book of the Fixed Stars (c.964) contained a star catalogue and atlas based on Ptolemy's*Almagest, revised in the spirit of ...
Abell Catalogue

Abell Catalogue  

A catalogue of 2712 rich clusters of galaxies published in 1958 by the American astronomer George Ogden Abell (1927–83) from inspection of the Palomar Observatory Sky Survey photographs. The ...
Abell cluster

Abell cluster  

A cluster of galaxies listed in the Abell Catalogue. To appear in the catalogue, a cluster must satisfy selection criteria which include containing more than 50 galaxies and having a dense ...
Abell clusters

Abell clusters   Reference library

The Oxford Companion to Cosmology

Reference type:
Subject Reference
Current Version:
2008

George Abell is best remembered for his catalogue of clusters of galaxies, a result of his PhD work at the

Abell radius

Abell radius  

A radius of about 2 megaparsecs within which at least 50 galaxies of a particular range of brightness must be found if the cluster is to qualify as an Abell cluster.
Abell Catalogue

Abell Catalogue   Quick reference

A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

A catalogue of 2712 rich clusters of galaxies published in 1958 by the American astronomer George Ogden Abell (1927–83...

Abell cluster

Abell cluster   Quick reference

A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018
A cluster of galaxies listed in the *Abell Catalogue. To appear in the catalogue, a cluster must satisfy selection criteria which include containing more than 50 galaxies and having a ... More
Abell radius

Abell radius   Quick reference

A Dictionary of Astronomy (3 ed.)

Reference type:
Subject Reference
Current Version:
2018

A radius of about 2 megaparsecs within which at least 50 galaxies of a particular range of brightness must be found if the cluster is to qualify as an ...

aberration

aberration  

The small apparent difference between the observed direction of a star and its true direction (see diagram). It is due to the combined effect of the observer's motion across the path of incoming ...

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