What is a planet? NASA Article

What does the word 'planet' originally mean according to ancient Greek?

• Wanderer

• Light

• Sphere

• Star

What three things must a celestial body do to be considered a planet by the IAU?

• Orbit a star, emit it's own light, and "clear" it's orbit of other star orbiting objects

• Orbit a star, have at least one natural satellite (moon), and be spherical in shape

• Orbit a star, be the largest object in its orbit, and be named after a Greek god

• Orbit a star, have a spherical shape, and "clear" its orbit of other star orbiting objects

Which of the following was considered a planet by the ancient Greeks but is not a planet by modern definitions?

• Pluto

• Earth's Moon

• Neptune

• Mars

When was Uranus added as a planet?

• 1930

• 1846

• 2006

• 1781

What led to Pluto being reclassified from a planet to a dwarf planet?

• Its size compared to Mercury

• Discovery of the Kuiper Belt

• Its orbit around the Sun

• The invention of the telescope

What is a 'dwarf planet' according to the IAU?

• A celestial body that orbits a star other than the Sun

• A celestial body that has not cleared its orbit

• A satellite of a planet

• The smallest planet in a solar system

How many dwarf planets are recognized by the IAU?

• 10

• 2

• 5

• More than 100

What is the primary reason for the ongoing debate about the definition of a planet?

• The size of the celestial body

• The discovery of exoplanets

• Disagreements about classification criteria

• The number of moons a planet has

What does the scientific process involve?

• Questioning, hypothesizing, and changing ideas based on new discoveries

• Following a strict set of unchangeable rules

• Accepting all previous ideas without question

• Ignoring peer review

What is the significance of extrasolar planets, or exoplanets?

• They are all considered dwarf planets

• They are smaller than any planets in our solar system

• They can only be found in the Kuiper Belt

• They reside outside our solar system and orbit other stars