Pluto's new place is dwarf planet - Star Local: News

Pluto's new place is dwarf planet

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Posted: Friday, September 1, 2006 12:00 am

Controversy has once again resurfaced in regards to Pluto, formerly considered the ninth planet from the Sun in the solar system.

“In my teachings, I always taught the kids that there were nine planets,” said Paul Ballou, Mesquite ISD planetarium educator. “We would also talk about how Pluto did not really fit into that group and include historical reasons.”

The 26th General Assembly of the International Astronomical Union in Prague, Czech Republic, reclassified Pluto last week. It will now be considered a dwarf planet.

Science projects each year are produced and predictably many will create models of the solar system.

It is likely projects in the Mesquite ISD will be entered with only eight planets this year. Textbooks will continue to detail the former ninth planet.

“Textbooks will always lag behind,” Ballou said. “It is important for students to realize that science is a process. Things change. Our understanding of the universe changes.”

Pluto was discovered in 1930 by Clyde Tombaugh and for more than 75 years the debate has continued as to its merits as a planet.

The discovery of other trans-Neptunian objects produced renewed debate. UB313, nicknamed Xena, was discovered in 2003 and focused debate on the definition of a planet.

“The UB313 discovery is pretty much the reason why Pluto is now not considered a planet,” Ballou said.

Pluto joins Ceres and the Kuiper Belt, including UB313 which is larger than Pluto, as dwarf planets.

“When Pluto was first discovered, it made a big splash,” Ballou said.

Prior to 1930, students were learning of a solar system comprised of eight planets. Now, they will again.

Many astronomers, like Ballou, debated to validity of Pluto as a planet because of its eccentric orbit.

“Most planets have circular orbits,” Ballou said. “Their orbits are very close to being round. Pluto’s is much more oval. Pluto is also on an inclined orbit.”

Another trait of the orbit also provided reason to debate whether Pluto should be considered a planet.

“Every time Pluto completes an orbit, a portion of the orbit passes inside the orbit of Neptune,” Ballou said.

As such, Pluto moves closer in proximity to the sun and momentarily replaces Neptune as the eighth planet. Other planets don’t have intersecting orbits, Ballou explains.

Ballou also notes the mass of Pluto.

“It ranks 18th in our solar system in mass,” Ballou said. “Our moon has a larger mass than Pluto.”

It is smaller than several natural satellites or moons in the solar system. Pluto’s moon, Charon, are more nearly equal in size than any of the planet-moon combinations in the solar system.

“Whether we demote it or call it something else,” Ballou said. “It is what it is. It is Pluto.”

It’s not the only astronomical issue which has risen in the past month. An erroneous e-mail indicated that Mars would appear in the night sky on Aug. 27 and could be viewed as large as the moon.

“It was a hoax,” Ballou said. “I was asked that by my own father.”

His says the e-mail began to circulate in 2003, at a time when Mars was on an orbit closest to Earth in our lifetime.

“But it was misinformation three years ago,” Ballou said. “It was closer than it had been in tens of thousands of years, but even then it didn’t appear in the night sky as large as the moon. What they meant was that it could be viewed with a magnified telescope to be as large as the moon would be to the naked eye.”

There is one upcoming phenomenon which Ballou says is not a hoax and which will be a unique event this fall.

Mercury, the planet closest to the sun, will cross in front of the Sun’s surface in the daytime and can be viewed with a telescope and proper filter.

Contact managing editor Brian Porter at bporter@acnpapers.com.

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