Skywatcher Challenge: The Observing Planets Quiz

If an object is in orbit, then a centripetal force must be pulling it toward the center. If we look at planetary systems, then gravity is the universal force of attraction between masses. Therefore, gravity provides the pull needed to keep a moon from flying off into space.

If the moon reflects sunlight, then one half is always lit. If the moon orbits Earth, then our viewing angle of that lit half changes. Therefore, the phase we see depends on how much of the sunlit side is visible from our specific position.

If stars are extremely far away, then they appear stationary to the naked eye. If planets are much closer and orbiting the Sun, then their relative positions change noticeably. Therefore, we observe planets wandering through different constellations over weeks or months.

If a planet has rings made of highly reflective ice and rock, then they will be bright. If Saturn possesses the largest and most dense collection of these particles, then it will have the most visible ring system compared to the faint rings of other gas giants.

If we define celestial bodies by their orbital parent, then a planet must orbit a sun or star. If a body orbits a planet instead, then it is classified as a satellite or moon. Therefore, the primary distinction is the object they are gravitationally locked to.

If Galileo Galilei was the first to observe these four moons (Io, Europa, Ganymede, and Callisto) in 1610, then they are named in his honor. Therefore, they are universally referred to as the Galilean moons in astronomy.

If a planet is covered in thick sulfuric acid clouds, then it has a high albedo or reflectivity. If it reflects a high percentage of sunlight back toward Earth, then it will appear as the brightest star-like object in the sky.

If a lunar eclipse involves the moon going dark, then it must be entering a shadow. If the Earth is between the Sun and the Moon, then Earth casts that shadow on the Moon. If the Moon were between the Earth and Sun, it would be a solar eclipse.

If you want to see small details, then you must separate light rays that are very close together. If a telescope has a larger aperture or opening, then it can capture more detail and provide better resolution. Therefore, aperture is more critical for detail than just making an image bigger.

If we exclude Earth, then we look for planets bright enough to see without tools. If Mercury, Venus, Mars, Jupiter, and Saturn are all close enough or large enough to reflect significant sunlight, then they are visible to the naked eye.

If Mars has a high concentration of iron minerals in its soil, then those minerals can react with trace oxygen. If iron rusts, then it turns a reddish-orange color. Therefore, the distinct hue we observe from Earth is due to this chemical composition.

If the planets and Earth all orbit the Sun in roughly the same flat plane, then from our perspective, they will all appear on the same narrow track. Therefore, this path is known as the ecliptic.

If a planet is a gas giant, then it has immense gravity. If it has immense gravity, then it can capture many moons and hold onto debris that forms rings. Therefore, having numerous satellites is a defining trait of the outer solar system.

If Jupiter is a gas giant, then it has no solid surface for features to sit on. If we observe a swirling, reddish oval that has persisted for centuries, then it must be an atmospheric phenomenon. Therefore, it is a high-pressure cyclonic storm.

If we always see the same side of the Moon, then it must be tidally locked. If it is tidally locked, then its rotation time must exactly match its orbital time. Therefore, the statement is true.

If the moon is between the Earth and Sun, then the side facing us is in total darkness. If no sunlight is reflecting from the side we see, then the moon is invisible in the night sky. This phase is called the New Moon.

If Mercury is the closest planet to the Sun, then its orbit is very tight. If it is close to the Sun, then from Earth it only appears shortly before sunrise or after sunset. Therefore, the Sun's glare usually hides it from view.

If scientists look for life, then they look for liquid water. If Europa shows cracks and movements in its ice suggesting a warm interior, then a sub-surface ocean is likely. Therefore, it is a top priority for space exploration.

If Earth orbits the Sun faster than an outer planet, then we eventually pass or lap that planet. If we pass the planet, then from our moving perspective, it looks like it is moving backward. Therefore, this optical illusion is called retrograde motion.

If a moon is large enough and cold enough, then it can hold onto an atmosphere. If Titan has nitrogen and methane, then methane can exist as a liquid on its surface. Therefore, it is the only moon known to have substantial clouds and surface liquids.