Astronomy Test 2

Front 1

Altitude

Back 1

The angular distance of a point from the horizon.

Front 2

Azimuth

Back 2

The angle that is measured around the celestial sphere, starting at the vertical circle passing through the north point.

Front 3

Diurnal Circle

Back 3

The apparent path that an object appears to follow as a result of the rotation of the Earth around its axis.

Front 4

Hour Angle

Back 4

The angular distance of an object measured westward from the Local Celestial Meridian.

Front 5

Craters

Back 5

Most are the result of meteorite impacts, although a few are volcanic in origin.

Front 6

Caldera

Back 6

A large opening in the top of a volcano that may contain several vents.

Front 7

Plain

Back 7

A relatively flat region of large expanse.

Front 8

Ridge

Back 8

A pressure fold in the lava plain caused by cooling and shrinking.

Front 9

Rays

Back 9

Bright streaks emanating from an impact crater. In reality, they are radial bands of small secondary craters produced by material ejected from a larger impact site.

Front 10

Rills

Back 10

Channel like grooves forming complex patterns on a planetary surface. They appear to be similar to meandering river gorges. Some are chains of collapse craters caused by sinking along a fault line.

Front 11

Regolith

Back 11

A granular or powder like material forming a layer on the surface of a planetary body. This material is produced by numerous small meteorites strinking the surface.

Front 12

Brown Dwarfs

Back 12

Bodies that form with a mass less than the Kumar Limit, but are larger than 17 Jupiter masses.

Front 13

Kumar Limit

Back 13

Frist calculated by the Indian astrophysicist Kumar, this is the minimum mass a body needs to be classified as a star. This mass, estimated at 0.07 solar masses, is the minimum mass still large enough for its gravity to compress the body to a central density high enough for Thermonuclear Fusion to occur.