One of the points of intersection between the ecliptic and the celestial equator. When the sun is at one of these two points, the length of day and night are equal everywhere on the earth. The sun is [..]

A change in wavelength of emitted light when the source of light is placed in a magnetic field.

The point on the celestial sphere directly overhead.

A band of the celestial sphere, 8° wide, on each side of the ecliptic. The zodiac is divided lengthwise into twelve equal sections; each 30° section is popularly identified by a “sign of the zodiac.” [..]

The name given a U.S.S.R. series of space probes made to collect data about Venus.

A white star of low luminosity, small size, and extremely high density.

Greenwich time. The mean solar time at the 0° meridian passing through Greenwich, England. Used as a world standard.

Two doughnut-shaped regions surrounding the earth in which high-energy particles are trapped.

The ordinary year. The year used in everyday life.

The dark shadow cast by a planet or a satellite.