ELA 5.4 Anthology When is a Planet Not a Planet

Cause: The International Astronomical Union (IAU) made an announcement in 2006. Effect:

• Pluto gained a new moon.

• The sentence used to remember the planets no longer worked.

• Scientists discovered a new planet.

• Pluto's orbit became more circular.

Cause: The Sun's heat blasted away much of the gas from the planets closest to it. Effect:

• The gas giants formed.

• Pluto became the ninth planet.

• The terrestrial planets were formed.

• The Kuiper Belt was discovered.

Cause: Astronomers discovered that Pluto was dense and had a rocky core. Effect:

• Pluto's orbit became more regular.

• Scientists created a new sentence to remember the planets.

• It raised questions about why Pluto was rocky.

• Pluto was confirmed to be a gas giant.

Cause: Astronomers found other objects in the Kuiper Belt that were similar in size to Pluto. Effect:

• Pluto was reclassified as a dwarf planet.

• The IAU decided Pluto was a planet.

• Scientists stopped searching for new planets.

• Pluto's distance from the Sun decreased.

Which of the following best describes how the understanding of Pluto changed "over time," as discussed in the article?

• Pluto was consistently considered the ninth planet and its status never changed.

• Pluto was initially considered a planet, then reclassified, and scientists' understanding of its composition evolved.

• Pluto's size and distance were accurately known from the time of its discovery.

• Scientists always agreed on Pluto's classification, but their understanding of other Kuiper Belt objects changed.

Which of the following patterns is described in the article?

• All planets orbit the Sun in perfect circles.

• Planets closer to the Sun are larger than those farther away.

• The gas giants are primarily composed of rock and minerals.

• Planets in the outer solar system tend to have more gas and ice.

What trend in astronomical discovery is highlighted in the article?

• A trend toward relying solely on human observation through telescopes.

• A trend toward using more advanced technology like robotic telescopes and computer analysis.

• A trend toward naming planets after Greek gods and goddesses.

• A trend toward decreasing interest in discovering new objects in the solar system.

Which "big idea" is most central to the article?

• The importance of memorizing facts.

• The unchanging nature of scientific knowledge.

• The idea that scientific knowledge can evolve and change.

• The superiority of older scientific theories.