Space exploration began with the launch of Sputnik and Astrophysics was born as the application of physics to the phenomena observed by Astronomy, which etymologically means laws of the stars.
There are 2759 entries in this glossary.| Term | Definition |
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| B Star |
A star of spectral type B. B stars have surface temperatures in the range 11,000 - 25,000 K and are bluish white in colour. The most prominent features in their spectra are absorption lines of neutral helium. The Balmer lines of hydrogen are also present, being stronger the cooler the star. Examples of B stars are Rigel and Spica.
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| B-Type Asteroid |
A subclass of C-type asteroids, distinguished by higher albedo.
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| Baa |
Abbreviation for the British Astronomical Association.
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| Baade’s Window |
An area of sky around the globular cluster NGC 6522 in the constellation Sagittarius, which is particularly rich in stars. The German-American astronomer Walter Baade 1893-1960 drew attention to the area and correctly deduced that it is a region in the disc of our Galaxy relatively clear of interstellar material through which very distant stars in the Galaxy’s nuclear bulge can be seen.
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| Background Radiation |
cosmic background radiation.
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| Backscattering |
The scattering of radiation or particles through angles greater than 90° relative to the direction of incidence.
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| Baikonur |
The manned space-flight centre established by the former Soviet Union. It is situated north-east of the Aral Sea in Kazakhstan.
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| Baily |
A large, highly eroded lunar crater, 298 kilometres 185 miles in diameter.
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| Baily’s Beads |
A phenomenon observed during the progress towards a total solar eclipse, just before totality and again just after totality. As the Moon gradually obscures the disc of the Sun, the final thin crescent appears to be broken up into a string of bright beads because the mountains and valleys on the Moon make its limb uneven. The English astronomer Francis Baily 1774-1844 drew attention to the phenomenon at the solar eclipse of 1836.
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| Baker-Nunn Camera |
A form of Schmidt camera designed for the photography of artificial satellites.
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| Baker-Schmidt Telescope |
A form of Schmidt camera, incorporating design modifications by J. G. Baker to eliminate aberrations and distortion.
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| Balmer Decrement |
A marked intensity drop at a wavelength of about 365 nanometres in the continuous spectrum of a star or other astronomical object in which absorption by hydrogen occurs. The individual Balmer lines of atomic hydrogen become closer with decreasing wavelength until they merge. The wavelength of 365 nanometres corresponds to the energy required to ionize a hydrogen atom when the electron is originally in the second energy level of the atom. At shorter wavelengths higher energies the hydrogen effectively causes continuous absorption.
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| Balmer Lines Balmer Series |
A series of spectral lines in the spectrum of atomic hydrogen. The lines are termed H alpha, H beta, H gamma, and so on, starting with the line of longest wavelength, which is at 656.3 nanometres. The lines become more closely spaced with decreasing wavelength, merging at the series limit of 365 nanometres.
See also: Balmer decrement.
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| Bamberga |
Asteroid 324, diameter 252 km, discovered by J. Palisa in 1892.
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| Band Spectrum |
A spectrum characterized by bands of closely spaced absorption lines in a continuous spectrum. Band spectra result from the presence of molecules rather than single atoms.
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