Question

1. choose all that apply. choose two facts about dwarf planets. a dwarf planet is any planet smaller than mars. they are round objects smaller than earth’s moon. they orbit the sun but have not cleared their orbit of other objects. dwarf planets are rocky objects found beyond pluto’s orbit. 2) choose the best answer. why was pluto reclassified as a dwarf planet? a visiting space probe revealed that pluto was less dense than thought, and thus did not have enough mass to be a planet. discovery of unusual new objects led scientists to reconsider the definition of a planet. it was a political move to remove power from the international astronomical union.

Explanation:

Sub - question 1

To determine the correct facts about dwarf planets, we analyze each option:

• Option 1: A dwarf planet is defined as a celestial body that is in hydrostatic equilibrium (round) and orbits the Sun, but has not cleared its orbital neighborhood. Also, dwarf planets like Pluto are smaller than Mars. So this is a correct fact.
• Option 2: Earth's moon is a natural satellite and not a dwarf planet. Dwarf planets are independent celestial bodies orbiting the Sun. So this is incorrect.
• Option 3: One of the key criteria for a dwarf planet is that it has not cleared its orbit of other objects (unlike regular planets which have cleared their orbits). This is a correct characteristic of dwarf planets.
• Option 4: Dwarf planets can be composed of various materials, not just rocky. For example, Pluto has a significant amount of ice. So this is incorrect.

So the correct options for sub - question 1 are "A dwarf planet is any planet smaller than Mars" and "They orbit the sun but have not cleared their orbit of other objects".

Sub - question 2

To determine why Pluto was reclassified as a dwarf planet, we analyze each option:

• Option 1: A visiting space probe's discovery about Pluto's density did not lead to its reclassification. The reclassification was due to the definition of a planet.
• Option 2: The discovery of other objects (like Eris) in the Kuiper belt that were similar in size to Pluto led scientists to re - evaluate the definition of a planet. A planet must clear its orbital neighborhood, and Pluto did not meet this criterion. So this is the correct reason.
• Option 3: The reclassification of Pluto was a scientific decision based on astronomical criteria, not a political move.

Answer:

1. The correct options are:

• A. A dwarf planet is any planet smaller than Mars
• C. They orbit the sun but have not cleared their orbit of other objects

1. The correct option is:

• B. Discovery of unusual new objects led scientists to reconsider the definition of a planet