Astro Glossary

Space Technology

Space Travel

Space Weather

Spectroscopy

A technique used by astronomers that allows them to determine the properties, such as composition, temperature, and motion through space, of celestial objects by analyzing the spectra of celestial objects. For example, because each atomic element absorbs and emits light in a unique set of wavelengths, the astronomer can sift through the spectrum of a star and determine what elements are present in the star’s atmosphere. From the shapes and depths of spectral lines, the astronomer can calculate fundamental qualities of a star, such as how fast the gases churn through the stellar atmosphere or the star’s effective temperature. An astronomer may also be interested in correlations between the abundances of certain elements and the physical behavior of the star, the age of the star, or the abundances of other elements. For instance, compared with the Sun, stars with low amounts of iron are also low in almost every other element with respect to hydrogen. Spectroscopy is performed by astronomers with instruments called spectrographs.

Speed of Light

The maximum velocity for everything in the universe; 186,282.397 miles (299,792.458 km) per second, or fast enough to go to the Moon and back in less than three seconds.

Spica

A blue-white giant star 250 light-years away in the constellation Virgo.

Spiral Galaxies

Spitzer Space Telescope

Spitzer Telescope has provided a dramatic new view of the Milky Way galaxy. It has mapped giant stellar nurseries, and revealed thousands of infant stars, as well as thousands of old stars, which have wrapped themselves in cocoons of gas and dust. Spitzer has also helped produce the best map of the Milky Way to date. The map reveals that the Milky Way probably has two major spiral arms wrapping around a long “bar” of stars in its center.

Star Catalogs and Charts

Monthly star charts are for sale in the StarDate store.

Star Clusters

A grouping of the same types of astronomical objects. For example, stars in the Milky Way can group together into open clusters or globular clusters. Galaxies also group together into cluster of galaxies, and the clusters of galaxies group together into superclusters of galaxies.