If you were in elementary school before 2006, there's a good chance you had to memorize the order of the 9 planets in our solar system; Mercury, Venus, Earth, Mars, Jupiter, Saturn, URinus—also pronounced UrANUS, and finally Neptune, and Pluto. Now, if you're currently in elementary school, you might be saying, "Wait, there were nine planets?”

So, what happened to Pluto? It’s not like it’s gone anywhere. It’s still out there on the edge of the solar system, as cold and far away as ever, so what changed?

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TIMESTAMPS:

What happened to Pluto? 0:46

What does the word planet mean? 1:26

How large is Pluto? 3:12

If it has a satellite, is it a planet? 4:03

The discovery of Eris 4:59

What does it take to be a planet now? 5:31

Scientists who believe Pluto is a planet 6:11

#pluto #spacefacts #brightside

SUMMARY:

-Pluto hasn't changed, but our understanding of it has. We know way more about space than we did one hundred years ago.

-From the age of Galileo to the nineteenth century, planet referred to any object orbiting the Sun. So astronomers kept finding countless planets.

-We know that Pluto is only one 459th the size of planet Earth, making it smaller than the moon and only about twice the size of the former planet Ceres.

• Charon may be smaller than Pluto, but not that much smaller. One half the diameter might seem like a big difference, but not compared to the differences in size between the other planets and their moons.

-While Eris is slightly smaller than Pluto, initial measurements placed it as somewhat more massive. This added one more strike against Pluto’s status as a planet.

-First, a planet must orbit the Sun. Number two is that the object must be a sphere, or at least nearly so. Pluto checks the first two boxes but runs into trouble with number three, which says a planet must have "cleared the neighborhood" around it.

-Scientists who disagree with the IAU’s ruling and want to call Pluto a planet once more propose that any object with enough mass to maintain a spherical, or nearly spherical, shape would qualify as a planet.

Preview photo credit:

Global Mosaic of Pluto in True Color: By NASA/JHUAPL/SwRI, https://www.nasa.gov/image-feature/gl...

Animation is created by Bright Side.

Music by Epidemic Sound https://www.epidemicsound.com/

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