MAA Glossary

S


Satellit:
Object in orbit around a planet.

Shooting star:
Popular term for meteor.

Sideral time:
Star time; the hour angle of the vernal equinox.

Solar wind:
Gases driven from the sun as the result of the bioling activity. Charged particles of the solar wind hitting the upper parts of the earthern atmosphere is the cause of the polar lights.

Solstice:
The position of the sun when farthest north (summer solstice) or farthest south (wintern solstice).

Spectral type:
The classification of stellar spectra (see Spectrum). The classification nowadays used is the Harvard Classification, where stars were given one of the following letters according to the appearence of spectral lines in their spectra: O B A F G K M R N S. One of the most favourite wordings to remember this sequence of letters goes as follows:

Spectrum:
Starlight, dispersed according to color or wave length by the means of a prism or other device, is known as a spectrum.
(This is of course not only true for starlight.)

Star:
A hot ball of glowing gas. (see also sun)

Stereographic projection:
A map of a sphere as projected upon a tangent plane from a point diametrically opposite to the point of tangency.

Sun:
A star of the spectral type G0; the center of the solar system. Sometimes used generally as synomym for star.

Sun, active

Sun, quiet

Sunspot:
Cooler dark aerea of visible solar surface.

Supernova:
Stars with masses more than 1.4 solar masses face a spectacular increase in brightness, when the nuclear fusion in the center of the star comes to an end. While the core collapses the atmosphere expands rapidly (through shockwaves ?).

Supernova Remnant:
What is left after a supernova has taken place. The supernova remants are the expanding atmosphere as well as the star left behind. Depending on the mass of the progenitor this star can be neutron star or a black hole (the existence of the last one is still a little bit hypothetical). A good example for a supernova remant is the Crab Nebula, M 1.