Astronomy Ch 3

Front 1

annular eclipse

Back 1

A solar eclipse in which the solar photosphere appears around the edge of the moon in a bright ring, or annulus. The corona, chromosphere, and prominences cannot be seen. (p. 37)

Front 2

aphelion

Back 2

The orbital point of greatest distance from the sun. (p. 29)

Front 3

apogee

Back 3

The point farthest from Earth in the orbit of a body circling Earth. (p. 37)

Front 4

autumnal equinox

Back 4

The point on the celestial sphere where the sun crosses the celestial equator going southward. Also, the time when the sun reaches this point and autumn begins in the northern hemisphere - about September 22. (p. 28)

Front 5

chromosphere

Back 5

Bright gases just above the photosphere of the sun. (p. 36)

Front 6

corona

Back 6

On the sun, the faint outer atmosphere composed of low-density, high-temperature gas. (p. 37)

Front 7

diamond-ring effect

Back 7

During a total solar eclipse, the momentary appearance of a spot of photosphere at the edge of the moon, producing a brilliant glare set in the silvery ring of the corona. (p. 37)

Front 8

ecliptic

Back 8

The apparent path of the sun around the sky. (p. 26)

Front 9

evening star

Back 9

Any planet visible in the sky just after sunset. (p. 30)

Front 10

lunar eclipse

Back 10

The darkening of the moon when it moves through Earth's shadow. (p. 31)

Front 11

Milankovitch hypothesis

Back 11

Suggestion that Earth's climate is determined by slow periodic changes in the shape of its orbit, the angle of its axis, and precession. (p. 40)

Front 12

morning star

Back 12

Any planet visible in the sky just before sunrise. (p. 30)

Front 13

node

Back 13

The points where an object's orbit passes through the plane of Earth's orbit. (p. 39)

Front 14

penumbra

Back 14

The portion of a shadow that is only partially shaded. (p. 31)

Front 15

perigee

Back 15

The point closest to Earth in the orbit of a body circling Earth. (p. 37)

Front 16

perihelion

Back 16

The orbital point of closest approach to the sun. (p. 29)

Front 17

photosphere

Back 17

The bright visible surface of the sun. (p. 36)

Front 18

prominence

Back 18

Eruption on the solar surface. Visible during total solar eclipses. (p. 37)

Front 19

revolution

Back 19

Orbital motion about a point located outside the orbiting body. See also rotation. (p. 24)

Front 20

rotation

Back 20

Motion around an axis passing through the rotating body. See also revolution. (p. 24)

Front 21

Saros cycle

Back 21

An 18-year, 11-1/3-day period after which the pattern of lunar and solar eclipses repeats. (p. 39)

Front 22

sidereal period

Back 22

The time a celestial body takes to turn once on its axis or revolve once around its orbit relative to the stars. (p. 33)

Front 23

solar eclipse

Back 23

The event that occurs when the moon passes directly between Earth and the sun, blocking our view of the sun. (p. 35)

Front 24

summer solstice

Back 24

The point on the celestial sphere where the sun is at its most northerly point. Also, the time when the sun passes this point, about June 22, and summer begins in the northern hemisphere. (p. 28)

Front 25

synodic period

Back 25

The time a solar system body takes to orbit the sun once and return to the same orbital relationship with Earth. That is, orbital period referenced to Earth. (p. 33)

Front 26

umbra

Back 26

The region of a shadow that is totally shaded. (p. 31)

Front 27

vernal equinox

Back 27

The place on the celestial sphere where the sun crosses the celestial equator moving northward. Also, the time of year when the sun crosses this point, about March 21, and spring begins in the northern hemisphere. (p. 28)

Front 28

winter solstice

Back 28

The point on the celestial sphere where the sun is farthest south. Also the time of year when the sun passes this point, about December 22, and winter begins in the northern hemisphere. (p. 28)

Front 29

zodiac

Back 29

A band centered on the ecliptic and encircling the sky. (p. 27)