Poor, Poor Pluto

Contributor: Nichole Brooker. Lesson ID: 11754

No one likes to be removed from a team or be disqualified from a race or otherwise made to feel "small." Think how poor past-planet Pluto feels! Learn about this big rock named by an 11-year-old girl!


Space Science and Astronomy

learning style
Kinesthetic, Visual
personality style
Grade Level
Primary (K-2)
Lesson Type
Quick Query

Lesson Plan - Get It!


Did you know that, before 2006, Pluto was the ninth planet in the solar system? Where did it go?

solar system

In 2006, poor Pluto was demoted from a planet in the solar system to a dwarf planet!

In 1930, Pluto was discovered by Clyde Tombaugh, then named by an 11-year-old girl who thought Pluto should be named after the Roman god of the underworld.


In 1999, a group of scientists tried to classify Pluto as a comet but that wasn't right, either. Poor Pluto has been re-classified and called many different things, but in 2006, Pluto's status was officially changed to a dwarf planet. It was decided that Pluto wasn't big enough to be a planet, and the way it rotated around the sun was not the "right" way to be considered a planet.

What is a dwarf planet? According to NASA, a dwarf planet is a celestial body that:

  • orbits the sun.
  • has enough mass to assume a nearly-round shape.
  • has not cleared the neighborhood around its orbit.
  • is not a moon (A moon is defined as something that rotates around something else, like a planet or a star.).

Pluto is considerably smaller than the smallest planet, Mercury. In fact, it is less than half the size of Mercury. Pluto is also smaller than seven of the moons in the solar system. It is 23 the size of the Earth's moon. The photo below is a comparison of Pluto with other planets and moons:

Pluto size comparison

Image by NASA is in the public domain.

Although Pluto was demoted from being a planet, it did inspire a new category of small planets named "plutoids." These are small planets that are orbiting the sun beyond Neptune. At least Pluto inspired something in the solar system!

There is a huge telescope called the Hubble Space Telescope that takes pictures of many different things in space. It has provided the best pictures of Pluto, but because the dwarf planet is so far away, it is very difficult to get accurate, clear pictures of it. Depending on the orbits of the two bodies, Pluto is anywhere from 2.66 to 4.67 billion miles away from Earth.

solar system

Pluto has four moons. One of its moons is about half the size of the planet, so some astronomers have called Pluto and its moon, Charon, a double-planet system.

Pluto's moons

One day on Pluto takes six-and-a-half Earth hours, and it takes 248 Earth years to go around the sun and complete one year.

The average temperature on Pluto is –375 to –400 degrees Fahrenheit! Now that is FRIGID! It is hundreds of degrees colder than the temperatures at the North and South Poles on Earth.

frozen man

The pictures that we have of Pluto show mountains, valleys, plains, craters, and maybe glaciers.

artist's impression of Pluto's surface

Image by European Southern Observatory, via Wikimedia Commons, is licensed under the CC BY 4.0 license.

The gravity on Pluto is a lot less than that on Earth. If you weighed 100 pounds on Earth, you would only weigh 7 pounds on Pluto!

Pluto is unique in the way it orbits the sun. Most planets orbit in a near-circle but Pluto orbits the sun in an oval shape.

Pluto's orbit

Image by NASA is in the public domain.

Pluto's demotion from planet to dwarf planet made some people upset because they felt that we should just leave Pluto alone. The fact is that changing Pluto's classification has made NASA and astronomers rethink how things are classified. Always learning and adjusting is important in life and even in space!

Review what you have learned about Pluto with this activity:

Did you find all of the answers? If not, review the above information. For more information about Pluto, check out All About Pluto and Dwarf Planets for Kids: Astronomy and Space for Children – FreeSchool (below):


In the Got It? section, you will use the information you learned to create a fun project about Pluto.

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