Ch 28Ch 28

Tools of AstronomyTools of Astronomy

EclipticEcliptic

is the plane in which Earth orbits is the plane in which Earth orbits about the Sun.about the Sun.

PerigeePerigee

is the closest point in the Moon’s orbit is the closest point in the Moon’s orbit to Earth.to Earth.

is the farthest point in the Moon’s orbit is the farthest point in the Moon’s orbit from Earth.from Earth.

ApogeeApogee

AlbedoAlbedo

the amount of the amount of sunlight that its sunlight that its surface reflectssurface reflects

– The Moon is The Moon is only about 0.07 only about 0.07 (7 percent) (7 percent)

– Earth’s average Earth’s average of 0.31 (31 of 0.31 (31 percent). percent).

RegolithRegolith is a layer of loose, ground-up rock on is a layer of loose, ground-up rock on

the surface of the Moon that formed the surface of the Moon that formed as a result of the heavy as a result of the heavy bombardment during its first 800 bombardment during its first 800 million years. million years.

HighlandHighland

are lunar regions that are light in color, are lunar regions that are light in color, mountainous, and heavily covered with mountainous, and heavily covered with craters.craters.

Mare (Mare (plural, plural, Maria)Maria)

are lunar regions that are dark, smooth are lunar regions that are dark, smooth plains, which on average are 3 km lower plains, which on average are 3 km lower in elevation than the highlands. in elevation than the highlands.

Impact CraterImpact Crater

were formed when were formed when objects from space objects from space crashed into the lunar crashed into the lunar surface. surface.

EjectaEjecta

is material is material blasted out blasted out during during impacts that impacts that fell back to fell back to the surface. the surface.

RillesRilles

are meandering, valleylike structures that are meandering, valleylike structures that are found in the Maria. are found in the Maria.

Summer SolsticeSummer Solstice

– occurs around June 21 each year when occurs around June 21 each year when the Sun is directly overhead at the the Sun is directly overhead at the Tropic of Cancer, which is at 23.5° N.Tropic of Cancer, which is at 23.5° N.

Winter SolsticeWinter Solstice

– occurs around December 21 each year occurs around December 21 each year when the Sun is directly overhead at the when the Sun is directly overhead at the Tropic of Capricorn which is at 23.5° S.Tropic of Capricorn which is at 23.5° S.

Autumnal EquinoxAutumnal Equinox

– occurs around occurs around September 21, September 21, halfway between halfway between the summer and the summer and the winter solstices the winter solstices when the Sun is when the Sun is directly over the directly over the equator.equator.

Vernal EquinoxVernal Equinox

– occurs around March 21, halfway between occurs around March 21, halfway between the winter and the summer solstices when the winter and the summer solstices when the Sun is directly over the equator.the Sun is directly over the equator.

Synchronous RotationSynchronous Rotation

– is the state at which orbital and rotational is the state at which orbital and rotational periods are equal. periods are equal.

– As the Moon orbits Earth, the same side As the Moon orbits Earth, the same side faces Earth faces Earth at all times because the Moon has a at all times because the Moon has a synchronous rotation, spinning exactly synchronous rotation, spinning exactly once each time it goes around Earth.once each time it goes around Earth.

Solar EclipseSolar Eclipse

occurs when the occurs when the Moon passes Moon passes directly between directly between the Sun and Earth the Sun and Earth and blocks our and blocks our view of the Sun.view of the Sun.

Lunar EclipseLunar Eclipse

occurs when occurs when the full Moon the full Moon passes passes through through Earth’s Earth’s shadow. shadow.

InterferometryInterferometry

– the the process of process of linking linking separate separate telescopes telescopes together together so that so that they act they act as one as one telescope. telescope.

SpinoffSpinoff

– technologies that were technologies that were originally developed for originally developed for use in space programs use in space programs that have been passed that have been passed on to commercial on to commercial industries for common industries for common use. use.

Refracting TelescopeRefracting Telescope

refractors, are refractors, are telescopes that telescopes that use lenses to use lenses to bring visible bring visible light to a light to a focus.focus.

Reflecting TelescopeReflecting Telescope

reflectors, are telescopes that bring reflectors, are telescopes that bring visible light to a focus with mirrors. visible light to a focus with mirrors.

RayRay

are long trails of ejecta that radiate are long trails of ejecta that radiate outward from some craters. outward from some craters.