• E-mail
• Print
• Comment
• Font Size
• Digg
• del.icio.us
• Discuss article

How Far is Far?

Posted on: Sunday, 27 February 2005, 03:00 CST

Here are some curious facts and puzzling questions about Pluto:

* Pluto is unimaginably far away. To get an idea of just how far, let one sheet of a roll of toilet paper represent 10,000,000 miles. The distance from Earth to the Sun is 9.3 sheets. Jupiter would be 48.4 sheets from the Sun and Saturn 88.7 sheets. Pluto (on average) would be 366.4 sheets! It takes 248 Earth years for Pluto to make just one trip around the Sun.

* From Pluto, the Sun looks like nothing other than a bright star. Does the solar wind-the stream of electrically charged particles that blasts out from the Sun-get all the way out to Pluto? What is it like?

* The distance from Earth to the Sun, about 93 million miles, is defined as one astronomical unit, or AU. Although Pluto's average distance from the Sun is 39.5 AU, at its closest point to the Sun it is 29.6 AU, and at its farthest point it is 49.6 AU from the Sun. For part of its 248-Earth-year year, Pluto is the 8th planet from the Sun, orbiting just inside the distance of Neptune's orbit from the Sun. This is one lopsided orbit! Why is this, when the rest of the planets' orbits are much more circular?

* Not only is Pluto's orbit highly elongated, it is tilted 17 from the plane of the ecliptic. What could have caused it to orbit so far above and below the swirling disk of dust from which the planets were formed?

* Because of its distance from the Sun, it's cold on Pluto! The average temperature on its surface is 233 below zero Celsius, or 387 below zero Fahrenheit.

* Pluto has an atmosphere, but only during the parts of its orbit when it is closest to the Sun. When Pluto gets farther from the Sun, the atmosphere freezes and falls to the surface like frost or snow, leaving no atmosphere at all. Right now, Pluto has an atmosphere. But what is it made of? What is its surface pressure? How fast does it escape into space? If we wait much longer to send a spacecraft, there may be no atmosphere left to study for a couple hundred years.

* Pluto's diameter is only about half the width of the United States. Charon's is about half of Pluto's. Charon is the largest moon compared to its planet of any moon in the solar system. For that reason. Pluto and Charon may be thought of as the only double- planet system in the solar system.

* Pluto and Charon seem very different. Pluto has some areas that appear very dark and some that appear very bright. Charon is much darker and more uniform. Scientists don't know what Pluto is made of. They think it may be a mixture of 70% rock and 30% water or other ices. Charon is less dense, so probably contains less rock. Why are the two so different?

* The whole Pluto-Charon system is tipped on its side. Like all planets, Pluto's spin axis stays pointed in the same direction as it orbits the Sun. But unlike all planets except Uranus, Pluto is tipped on its side. As for the rest of the planets, their axes of rotation stand more or less upright from the plane of their orbits.

Copyright International Technology Education Association Feb 2005

Source: Technology Teacher, The

More News in this Category