Astronomy Astronomy Celestial Mechanics and Orbits 2 — Questions and Answers
Question 1: What causes a solar eclipse?
- The Moon passes between Earth and the Sun, blocking sunlight (Correct answer)
- Earth passes between the Sun and Moon, casting a shadow
- The Sun's atmosphere temporarily dims its output
- The Moon's shadow falls on a different planet
Correct answer: The Moon passes between Earth and the Sun, blocking sunlight
A solar eclipse occurs when the Moon passes directly between Earth and the Sun, blocking all or part of the Sun's light from reaching Earth.
Question 2: What is tidal locking?
- When a moon's rotational period equals its orbital period, keeping one face toward the planet (Correct answer)
- When ocean tides synchronize with a moon's orbital period exactly
- When two bodies orbit in perfect synchrony around a common center
- When gravity slows a moon's orbit until it matches the planet's rotation
Correct answer: When a moon's rotational period equals its orbital period, keeping one face toward the planet
Tidal locking occurs when tidal forces slow a moon's rotation until it matches its orbital period, causing the same hemisphere to always face the parent planet.
Question 3: What is the Hill sphere of a planet?
- The region within which the planet's gravity dominates over the Sun's gravity (Correct answer)
- The zone around a planet where rings can form
- The spherical region swept clean of debris by a planet
- The region around a planet where its magnetic field is strongest
Correct answer: The region within which the planet's gravity dominates over the Sun's gravity
The Hill sphere is the region around a planet within which its gravitational influence dominates over that of the Sun, determining the stable zone for moons.
Question 4: What type of orbit does a geostationary satellite occupy?
- A circular equatorial orbit at ~35,786 km altitude (Correct answer)
- A polar orbit at ~800 km altitude
- An elliptical orbit with a period of 12 hours
- A retrograde orbit matching Earth's rotation
Correct answer: A circular equatorial orbit at ~35,786 km altitude
A geostationary orbit is a circular orbit at 35,786 km altitude above Earth's equator where a satellite's orbital period matches Earth's rotation, keeping it stationary over one location.
Question 5: What is the Roche limit?
- The minimum distance at which tidal forces will break apart a body held together only by gravity (Correct answer)
- The maximum distance from a star at which liquid water can exist
- The gravitational boundary between a planet's atmosphere and space
- The orbital distance at which a moon transitions from prograde to retrograde
Correct answer: The minimum distance at which tidal forces will break apart a body held together only by gravity
The Roche limit is the distance at which tidal forces from a massive body exceed the self-gravity of a smaller body, causing it to disintegrate.
Question 6: What is precession of the equinoxes?
- The slow wobble of Earth's rotational axis completing one cycle every ~26,000 years (Correct answer)
- The seasonal change in the position of the equinox points along the ecliptic
- The annual shift in Earth's perihelion point around its orbit
- The gradual change in the tilt of Earth's axial inclination
Correct answer: The slow wobble of Earth's rotational axis completing one cycle every ~26,000 years
Precession of the equinoxes is a gradual wobble of Earth's rotational axis, like a spinning top, caused by gravitational torques from the Moon and Sun, completing one cycle in about 26,000 years.
Astronomy Astronomy Celestial Mechanics and Orbits 2
What causes a solar eclipse?