Foundations of Astronomy

When we watch the nighttime sky, we find that

• the stars and constellations remain fixed in our sky, not rising or setting in a time as short as one night because they are so far away.
• most stars and constellations slowly rise in the east and set in the west.
• most stars and constellations slowly rise in the west and set in the east.
• all stars and constellations reach their highest point in the sky at midnight.

What is the phase of the Moon during a total lunar eclipse?

• New
• Full
• Gibbous
• First quarter

The Arctic Circle is defined as a line on the Earth where

• the Sun always shines, winter or summer.
• the Sun can be seen for 24 hours on at least one day of the year.
• the Sun is always 23.5 degrees or more above or below the horizon.
• the Sun never shines at any time of the year.

The Moon does not look completely dark when it is in the Earth's shadow during a total solar eclipse because

• of light reflected from the clouds on the Earth, the earthshine.
• atmospheric refraction bends red solar light onto the Moon.
• there are faint emissions from the tenuous lunar atmosphere, excited by solar wind bombardment.
• there is a remnant glow from the hot lunar surface.

If you follow a line through the "pointer stars" (the two stars in the bowl of the Big Dipper farthest from the handle) away from the open end of the dipper, the first moderately bright star you come to is

• Polaris, the North Star.
• Spica, in Virgo.
• Arcturus, in Bootes.
• Vega, in Lyra.

The reason that leap years have an extra day is to account for the fact that

• the Earth's rotation period is slowly increasing because of tidal effects.
• the year is not exactly equal to an integral number of days.
• the day is not exactly 24 hours because of the Earth's periodically varying rotation period.
• the length of the year varies with a period of four years because of precession.

The tilt angle of the Earth's spin axis to the direction perpendicular to the ecliptic (known as the ecliptic pole)

• is 90 degrees and fixed.
• varies rapidly through the year from 23.5 degrees to -23.5 degrees.
• is 23.5 degrees and fixed.
• is 0 degrees and fixed because this defines the ecliptic plane.

Seasonal variations on a planet's surface are caused by

• clouds that periodically form and disappear as the planet orbits the Sun.
• the tilt of the planet's spin axis with respect to the perpendicular to its orbital plane.
• volcanoes that erupt periodically because of tidal interactions and obscure the atmospheres of planets.
• the variation of the planet's distance from the Sun during its passage around its elliptical orbit.

The average distance from the Earth to the Sun, 149,600,000 km, can be written in shorthand notation as

• 1.496 x 10⁸ km.
• 1.496 x 10⁶ km.
• 1.496 x 10⁹ km.
• 1.496 x 10⁷ km.

The length of time for the Moon to move from new Moon to new Moon is known as one synodic month. Compared to one full orbital period with respect to the star background, or one sidereal month, this synodic month is

• about 2 days shorter.
• about twice as long.
• exactly the same length.
• about 2 days longer.