Question

Retrograde motion of superior planet always occurs when the planet is a) in conjunction with the moon b)brighter than average c)near the autumnal equinox d) near a solstice e) dimmer than average 2) The moon a) spins once on its axis relative to the sun every 23 hours 56 mins. b) spins once on it axis relative to the sun every 24 hours c) spins once on its axis relative to the sun every 29.5 days d) spins once on its axis relative to the sun every 365 days e)never spins on its axis 3) The planets a) move faster in their orbit around the sun in km/s, the closer they are to the sun b) are always located at the same right ascension and declination in the sky c) are always found along the celestial equator d) are always located at declinations greater than 60 degrees e) are always observed along the meridian

Answer 1

1. answer is option (a)

When a superior planet and the Earth have the same right ascension on the celestial sphere (i.e. the Earth, Sun and superior planet all lie along the same line), a superior conjunction occurs (elongation = 0 degrees). A superior planet is at opposition when it is on the opposite of the Earth to the Sun (elongation = 180 degrees).The superior planets exhibit retrograde motion during their orbits around the Sun.

2.answer is option (c)

The moon orbits the Earth once every 27.322 days. It also takes approximately 27 days for the moon to rotate once on its axis. As a result, the moon does not seem to be spinning but appears to observers from Earth to be keeping almost perfectly still. Scientists call this synchronous rotation.It takes 23 hours, 59 minutes and 4 seconds for the Earth to make one complete rotation on its axis.

27.3 days is the time taken taken for the Moon to circle the Earth once relative to the background stars. A sidereal month. One 360 degree turn on its axis.

The Moon rotates around the the Earth in the same direction the Earth rotates around the Sun. (Anti-clockwise looking down from the North Pole.)

In the time taken for the Moon to complete a 360 degree turn, the Earth has completed over 1/13th of its orbit around the Sun, meaning the sun appears almost 27 degrees East from where it was when the sidereal month started, and the moon still appears as a waning crescent.

It takes another 2.2 days for the Moon to catch up with the Sun to provide the next New Moon. 29.5 days for a Synodic month. New Moon to New Moon.

3. answer is option(a)

A planet's orbital speed changes, depending on how far it is from the Sun. The closer a planet is to the Sun, the stronger the Sun's gravitational pull on it, and the faster the planet moves. The farther it is from the Sun, the weaker the Sun's gravitational pull, and the slower it moves in its orbit.