Pluto: The Planet That Wasn't

NASA

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Poor Pluto!

It’s bad enough to be the runt of the group, but to be told after 75 years that you’re not even a member of the club - what an insult!

Pluto was first discovered in 1930. Until 2006, students were taught that it was the ninth and smallest planet in the solar system. Smaller than Earth’s moon, it is not even as wide as the United States.

Pluto is made up almost entirely of rock and ice. It is so far away from Earth that the NASA New Horizons spacecraft took almost 10 years to get very close to it. Pluto’s full orbit around the sun lasts almost 250 Earth years!

But as small as it is, as cold as it is, as far from the sun as it is, for all those years it was considered the ninth planet of the solar system... until Eris came around.

Eris was discovered in 2005. It is about the same size as Pluto. And like Pluto, it is part of the Kuiper Belt, a ring of objects that circle the outer edge of the solar system.

After Eris was discovered, scientists had to make a decision. Either Eris was the 10th planet in the solar system or it was not a planet at all! And if Eris weren’t a planet, could Pluto be considered one?

Scientists made new rules for what is counted as a planet, and decided that neither Pluto nor Eris qualified.

A new category was created: dwarf planet. The official list of planets in the solar system went from nine to eight, and Pluto and Eris became members of the dwarf planet club. So long for Planet Pluto—but at least it no longer has to be the littlest guy in the club. In fact, Pluto is one of the bigger dwarf planets! Maybe Pluto doesn’t have it so bad after all.

Comprehension Questions

1. Pluto used to be considered a planet. Today, what is it considered to be? 

1. It is considered to be a dwarf planet. 
2. It is considered to be a star. 
3. It is considered to be a comet. 
4. It is considered to be an asteroid. 

2. How does the text describe Pluto? 

1. Pluto is made up entirely of ice, and it is bigger than Venus. 
2. Pluto is made up entirely of rock and ice, and it is bigger than Earth's moon. 
3. Pluto is made up entirely of gas, and it is bigger than Earth's moon. 
4. Pluto is made up entirely of rock and ice, and it is smaller than Earth's moon. 

3. Read these sentences from the text.

After Eris was discovered, scientists had to make a decision. Either Eris was the 10th planet in the solar system or it was not a planet at all! And if Eris weren’t a planet, could Pluto be considered one?

Scientists made new rules for what is counted as a planet, and decided that neither Pluto nor Eris qualified.

Based on this information, what did the discovery of Eris make scientists do? 

1. The discovery of Eris made scientists rethink the rules for what is counted as a star. 
2. The discovery of Eris made scientists rethink the rules for what is counted as a dwarf planet. 
3. The discovery of Eris made scientists rethink the rules for what is counted as a planet. 
4. The discovery of Eris made scientists add more planets to the group of planets. 

4. After Eris was discovered, scientists had to decide whether to count it as a planet. Why did this make them question whether Pluto should still be counted as a planet? 

1. because Pluto and Eris are both space objects 
2. because Pluto and Eris were discovered at the same time 
3. because Pluto and Eris are very different 
4. because Pluto and Eris are very similar 

5. What is the main idea of this text? 

1. Pluto was no longer considered a planet after the discovery of Eris made scientists come up with new rules for what is counted as a planet. 
2. Pluto is so far away from Earth that the NASA New Horizons spacecraft took almost 10 years to get very close to it. 
3. Eris is about the same size as Pluto, and like Pluto, it is part of a ring of objects that circle the outer edge of the solar system. 
4. Scientists come up with rules for what is counted as a planet and what is not. 

6. Read these sentences from the text.

A new category was created: dwarf planet. The official list of planets in the solar system went from nine to eight, and Pluto and Eris became members of the dwarf planet club. So long for Planet Pluto—but at least it no longer has to be the littlest guy in the club. In fact, Pluto is one of the bigger dwarf planets! Maybe Pluto doesn’t have it so bad after all.

What does the author mean by stating, "Maybe Pluto doesn't have it so bad after all"? 

1. Even though Pluto is no longer counted as a planet, it is in a new group called dwarf planets. 
2. Even though Pluto is no longer counted as a planet, it is one of the bigger dwarf planets. 
3. Even though Pluto is no longer counted as a planet, it is still part of the ring of objects that circle the outer edge of the solar system. 
4. Even though Pluto is now counted as a dwarf planet, it isn't alone as other space objects are counted as dwarf planets. 

7. Choose the answer that best completes the sentence.

After scientists made new rules for what is counted as a planet, Pluto was no longer considered a planet. _________, the official list of planets in the solar system went from nine to eight. 

1. Therefore 
2. Although 
3. On the other hand 
4. Especially 

8. According to the text, what were students taught about Pluto until 2006? (written answer)

9. What decisions did scientists have to make after Eris was discovered? 

(written answer)

10. Explain what made scientists decide to no longer count Pluto as a planet. Support your answer with evidence from the text. 

(written answer)

• Vocabulary
• 
  

consider  con · sid · er

Definition

verb

1. to think about something in a serious way. 

   She is considering getting a new job. 

Advanced Definition

transitive verb

1. to think about carefully; reflect on. 

   Have you considered what the rest of us should do? 

   I need time to consider the matter before making a decision. 

2. to think about as a possible selection or option. 

   Have you ever considered Florida for a vacation? 

   He's considering quitting his present job. 

   I don't think they even considered her for the position because of her lack of experience. 

3. to judge; deem; regard as. 

   I consider the project finished and don't intend to devote any more time to it. 

   I consider you my closest friend. 

   Shakespeare is considered to be one of the greatest writers of the English language. 

   She considered her friend's apartment huge compared with her tiny one in the city. 

   The parents didn't consider it necessary to take the child to the doctor. 

4. take into account; keep in mind. 

   His score was really not bad if you consider that he had never played golf before. 

   The judge will consider his lack of a criminal record in deciding what his punishment will be. 

5. to describe or talk about in a thoughtful way, looking at various aspects of a particular subject. 

   In tonight's lecture, the professor will consider the issues relating to the development of alternative fuels. 

6. to hold in esteem; regard highly. 

   He is highly considered by the whole community. 

intransitive verb

1. to reflect carefully or with deliberation. 

   This is a big decision, so let me consider for a moment. 

Spanish cognate

considerar: The Spanish word considerar means consider.

These are some examples of how the word or forms of the word are used:

1. The Indonesian government is considering a plan to increase commercial fishing in the east, near Papua, because Indonesia’s western seas are overfished. 
2. Ernest Shackleton solved the problems his men faced. He took a dangerous trip to save his crew. Today, many people consider him a hero. 
3. Native Americans also fought in the American Revolution. Most considered colonists to be a threat to their territory, and so they fought on the British side. 
4. Also, schools might want to consider, or think about, giving homework handouts and creating homework Web sites so kids do not have to take as many books home. 
5. At that time, our country was 13 separate colonies. The colonies were considered part of the country of England. The people living in the colonies wanted to have their own country. 
6. After dinner, and after everyone else had fallen asleep, Adam thought about waking Julia up to tell her about the phonograph. After considering it for a few minutes, he decided not to. 
7. While a publisher has not yet published his novel, the letter has been getting wider usage throughout the Detroit area, and Jerrold is considered the leading regional authority on the schwa and its uses. 
8. It’s easier to spot your ideal mousetrap, but you can’t start building until you’ve considered all of your constraints. Constraints are the things that stop you from doing whatever you want to meet your criteria. 
9. For many students around the country, their afternoon break is quickly becoming history. Nearly 40 percent of elementary schools have either eliminated or are considering eliminating recess, according to the American Association for the Child’s Right to Play. 
10. The laws came in response to the night of December, 16, 1773, when a patriot group called the Sons of Liberty tossed 342 chests of British tea into Boston Harbor. This was a protest against the Tea Act, a tax on tea which the colonists considered unlawful.