Science Scoops: Pluto: A Planet or Not?
by Amy Tao, art by Amy Loeffler
Poor Pluto. It's such a little pipsqueak of a planet, with a diameter of only about 1400 miles. (Compare that to Earth's 8000 miles!) It's even smaller than seven of the moons in the solar system, including Earth's. Pluto doesn't behave much like the other planets either. The path it travels around the Sun has a funny tilt and an unusual oval shape. And Pluto is made mostly of ice and rock—more like a comet than a planet. No wonder many scientists think it doesn't deserve to be called a planet.
To make matters worse, in October 2002, astronomers announced the discovery of Quaoar, a planet-shaped body with a diameter of about 800 miles. Quaoar is the biggest thing anyone's found in our solar system since, well, Pluto. But no one's calling Quaoar a planet. It's a KBO (short for Kuiper Belt object).
KBOs are small bodies that orbit the Sun in a region beyond Neptune called the Kuiper Belt. More than 600 KBOs have been identified since 1992, and scientists think there could be billions more. Some of them even have moons. Until now, the only real difference between KBOs and Pluto, which lies within the Kuiper Belt, has been size. Many of the visible KBOs are less than 100 miles in diameter.
This shows how big Pluto is compared to the U.S. Can a planet be smaller than a country?
But Pluto is not that much bigger than Quaoar. And scientists predict that more large KBOs will be found, perhaps some even larger than Pluto. Many astronomers argue, however, that even if we do find a Pluto-sized KBO, we should still consider Pluto a planet. What do you think?
The Sonoma State University Observatory
Imagine going to a school with its own observatory. If you are a student at Sonoma State University, that is exactly what you would be doing. The observatory at Sonoma State was opened in 1976 for use by students and faculty at the university. Even though you are in third grade, you can still visit the night sky. Throughout the year, the observatory is open for Public Viewing Nights. On these nights, people come to the observatory and look through its optical telescope to view planets, constellations, moons, and galaxies. In the summer, the observatory schedule includes viewings of Saturn, the Eagle Nebula, Jupiter, and even globular clusters. A globular cluster is a group of thousands or hundreds of thousands of stars.
The university built a robotic, computer-controlled telescope that is used in addition to its optical telescope. This computer-controlled telescope allows people to make and record a series of complex observations. The observatory does not normally use this telescope for Public Viewing Nights. But one day, you may be a college student at Sonoma State University and have the chance to study the stars.
Vocabulary
Sources:
- Astronomy Picture of the Day Index - Stars: Globular Clusters
- http://antwrp.gsfc.nasa.gov/apod/globular_clusters.html
- PDF file
- Sonoma State University Observatory
- http://www.phys-astro.sonoma.edu/observatory/