Astronomy

Front 1

Rotation

Back 1

Spin on an axis.

Front 2

Revolution

Back 2

The orbiting of one body around another

Front 3

Inclination

Back 3

Of an orbit, the angle of the plane of the orbit with respect to the ecliptic plane.

Front 4

Summer and Winter Solstice

Back 4

The point on the celestial sphere of northernmost or southernmost declination of the Sun in the course of a year; colloquially, the time when the Sun reaches that point.

Front 5

Vernal and Autumnal Equinox

Back 5

An intersection of the ecliptic and the celestial equator. The center of the Sun is geometrically above and below the horizon for equal lenghts of time on the two days of the year when the Sun passes the equinoxes; if the Sun were a point and atmospheric refraction were absent, then day and night would be of equal length on those days.

Front 6

Seasons

Back 6

One of the four natural divisions of the year, spring, summer, fall, and winter, in the North and South Temperate zones. Each season, beginning astronomically at an equinox or solstice, is characterized by specific meteorological or climatic conditions.

Front 7

Astromical Unit

Back 7

A unit of length used in measuring astronomical distances within the solar system equal to the mean distance from Earth to the sun, approximately 150 million kilometers (93 million miles).

Front 8

Waxing

Back 8

adj : (of the moon) becoming full; "the waxing moon passes from new to full"

Front 9

Waning

Back 9

To decrease gradually in size, amount, intensity, or degree; decline.

Front 10

Umbra/umbrae

Back 10

a) Of a sunspot, the dark central region

b) Of an eclipse shadow, the part from which the Sun cannot be seen at all.

Front 11

Penumbra

Back 11

a) For an eclipse, the part of the shadow from which the Sun is only partially occulted;

b) Of a sunspot, the outer region, not as dark as the umbra