Space Travel
22, May, 2012

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.
Search for glossary terms (regular expression allowed)
Begins with Contains Exact term
All | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

All

Term Definition
Fraunhofer Lines
The dark absorption lines in the spectrum of the Sun and, by extension, in the spectrum of any star. Many of the stronger ones were first mapped by Joseph von Fraunhofer 1787-1826, who also labelled some of the most prominent with letters of the alphabet. Some of these identifying letters are still commonly used in physics and astronomy, notably the sodium D lines and the calcium H and K lines.

Fraunhofer’s original 1817 designations of absorption lines in the solar spectrum
Letter
Wavelength nm
Chemical origin
A
759.37
Atmospheric O2
B
686.72
Atmospheric O2
C
656.28
Hydrogen α
D1
589.59
Neutral sodium
D2
589.00
Neutral sodium
D3
587.56
Neutral helium
E
526.96
Neutral iron
F
486.13
Hydrogen β
G
431.42
CH molecule
H
396.85
Ionized calcium
K
393.37
Ionized calcium
Note: Fraunhofer’s original observations did not resolve the components of his D line.