Unit 4 Critical Thinking: Exploring Dwarf Planets and Ice Giants

How do dwarf planets differ from regular planets in terms of their orbital characteristics?

• Dwarf planets have a clear path in their orbit.

• Dwarf planets do not have a clear path in their orbit.

• Dwarf planets are always closer to the Sun than regular planets.

• Dwarf planets have a faster orbital speed than regular planets.

Answer explanation

Dwarf planets differ from regular planets because they do not have a clear path in their orbit. This means their orbits can overlap with those of other objects, unlike regular planets that have cleared their orbital zones.

Tags

NGSS.MS-PS2-4

What are the primary components that classify Uranus and Neptune as ice giants?

• They are composed mainly of hydrogen and helium.

• They have a significant amount of water, ammonia, and methane ices.

• They have a rocky surface.

• They are primarily made of metallic hydrogen.

Answer explanation

Uranus and Neptune are classified as ice giants primarily because they contain a significant amount of water, ammonia, and methane ices, distinguishing them from gas giants like Jupiter and Saturn.

Why was the discovery of Eris problematic in terms of planetary classification?

• It was larger than Pluto, challenging the definition of a planet.

• It was located outside the solar system.

• It had an unusual orbit that was difficult to track.

• It was composed entirely of gas.

Answer explanation

The discovery of Eris was problematic because it was larger than Pluto, which challenged the existing definition of a planet and led to debates about what constitutes a planet in our solar system.

Explain how the definition of a planet excludes Pluto from being classified as a planet.

• Pluto does not orbit the Sun.

• Pluto does not have enough mass to be spherical.

• Pluto has not cleared its neighboring region of other objects.

• Pluto is not composed of rock and metal.

Answer explanation

Pluto is classified as a dwarf planet because it has not cleared its neighboring region of other objects, which is a key criterion in the definition of a planet established by the International Astronomical Union.

Discuss the historical reasons why planets were sometimes mistaken for stars.

• Planets emit their own light like stars.

• Planets have a fixed position in the sky like stars.

• Planets appear as bright points of light and do not twinkle like stars.

• Planets have a similar color spectrum to stars.

Answer explanation

Planets are often mistaken for stars because they appear as bright points of light in the sky and do not twinkle like stars. This distinct characteristic makes them seem similar to stars, despite their different nature.

Analyze the impact of Eris's discovery on the reclassification of celestial bodies in our solar system.

• It led to the reclassification of all planets as dwarf planets.

• It resulted in the creation of a new category for celestial bodies.

• It had no impact on the classification system.

• It confirmed that all celestial bodies are planets.

Answer explanation

The discovery of Eris led to the creation of the 'dwarf planet' category, as it was found to be similar in size to Pluto, prompting the need for a clearer classification of celestial bodies beyond the traditional planet definition.

Evaluate the significance of the ice composition in Uranus and Neptune's classification as ice giants.

• It makes them similar to terrestrial planets.

• It differentiates them from gas giants like Jupiter and Saturn.

• It has no impact on their classification.

• It makes them the smallest planets in the solar system.

Answer explanation

The ice composition of Uranus and Neptune, primarily made up of water, ammonia, and methane, distinguishes them from gas giants like Jupiter and Saturn, which are mostly hydrogen and helium. This composition is key to their classification as ice giants.

How does the current definition of a planet affect the classification of celestial bodies in the Kuiper Belt?

• It classifies all Kuiper Belt objects as planets.

• It excludes all Kuiper Belt objects from being planets.

• It allows only the largest Kuiper Belt objects to be classified as planets.

• It requires Kuiper Belt objects to clear their orbit to be classified as planets.

Answer explanation

The current definition of a planet requires that celestial bodies clear their orbit. Most Kuiper Belt objects do not meet this criterion, as they share their orbits with other debris, thus they cannot be classified as planets.

What reasoning led to the reclassification of Pluto as a dwarf planet?

• Its size was too large compared to other planets.

• Its orbit was too eccentric and inclined.

• It did not clear its orbit of other debris.

• It was composed mainly of gas.

Answer explanation

Pluto was reclassified as a dwarf planet because it did not clear its orbit of other debris, which is one of the key criteria for full planet status according to the International Astronomical Union's definition.

Strategize a method to distinguish between a planet and a star when observing the night sky.

• Look for twinkling; stars twinkle while planets do not.

• Measure the temperature; planets are hotter than stars.

• Check for color; planets are always red.

• Observe the size; planets appear larger than stars.

Answer explanation

Stars twinkle due to atmospheric turbulence, while planets generally shine steadily. This is a reliable method to distinguish between them when observing the night sky.