Dwarf Planets and Pluto

What is a dwarf planet?

• A) A celestial body that orbits the Sun

• B) A satellite of another planet

• C) A planet that has cleared its orbit

• D) A star

Answer explanation

A dwarf planet is defined as a celestial body that orbits the Sun but has not cleared its orbit of other debris. Therefore, the correct choice is A, as it accurately describes the nature of a dwarf planet.

Pluto was reclassified as a dwarf planet in which year?

• 2006

• 2010

• 2000

• 1995

Answer explanation

Pluto was officially reclassified as a dwarf planet by the International Astronomical Union in 2006, marking a significant change in its status from a full planet.

Pluto has a highly elliptical and tilted orbit, meaning it crosses which planet's orbit?

• Mars

• Jupiter

• Neptune

• Saturn

Answer explanation

Pluto's orbit is highly elliptical and tilted, allowing it to cross the orbit of Neptune. This unique characteristic means that for a period, Pluto can be closer to the Sun than Neptune.

Pluto's atmosphere is primarily composed of nitrogen, methane, and what other gas?

• Oxygen

• Carbon dioxide

• Carbon monoxide

• Hydrogen

Answer explanation

Pluto's atmosphere is primarily composed of nitrogen, methane, and carbon monoxide. While oxygen, carbon dioxide, and hydrogen are present in trace amounts, carbon monoxide is the correct additional gas in significant quantities.

Pluto has ice mountains and what other geographical feature?

• Deserts

• Frozen plains

• Volcanoes

• Rivers

Answer explanation

Pluto features frozen plains, which are vast, flat areas covered in ice. This geographical feature complements its ice mountains, highlighting the diverse icy landscape of the dwarf planet.

Haumea has an elongated, football-like shape and how many moons?

• One

• Two

• Three

• Four

Answer explanation

Haumea is known to have two moons, Hi'iaka and Namaka. This unique feature, along with its elongated shape, distinguishes it from other celestial bodies.

Makemake is known for its reddish color and lack of what?

• Moons

• Atmosphere

• Water

• Rings

Answer explanation

Makemake is notable for its reddish color and is unique in that it lacks moons, atmosphere, and water, making it distinct among dwarf planets.

Ceres is the largest object in which belt?

• Kuiper Belt

• Asteroid Belt

• Oort Cloud

• Van Allen Belt

Answer explanation

Ceres is the largest object in the Asteroid Belt, located between Mars and Jupiter. It is classified as a dwarf planet and is not part of the Kuiper Belt, Oort Cloud, or Van Allen Belt.

Which of the following is the primary reason Pluto is classified as a dwarf planet and not a planet?

• It is too small.

• It has a highly elliptical orbit.

• It has not cleared its orbital neighborhood.

• It is located in the Kuiper Belt.

Answer explanation

Pluto is classified as a dwarf planet because it has not cleared its orbital neighborhood, meaning it shares its orbit with other objects of similar size, which is a key criterion for full planet status.

Pluto was reclassified as a dwarf planet in 2006 by the International Astronomical Union because it failed to ________.

• maintain a stable orbit

• clear its orbital neighborhood

• have a spherical shape

• orbit the sun

Answer explanation

Pluto was reclassified as a dwarf planet because it failed to clear its orbital neighborhood, meaning it does not dominate its orbit and shares it with other objects, which is a key criterion for full planet status.