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Shvoong Home>Society & News>News Items>www.tribune.com.ng Summary

www.tribune.com.ng

Website Summary   by:israelme    
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Former planet pluto demoted again
SCIENTISTS have further demoted Pluto from being the biggest in the category of dwarf planet, a position it found itself a year ago. Based on calculations just published on the study of Dysnomia, the moon of Eris, another dwarf planet in the journal Science, astronomers no longer deem the planet as the largest of the solar system''s so-called dwarf planets . It was found to be smaller than recently discovered dwarf planet Eris. When the International Astronomical Union redefined planets last year, it created the new subcategory dwarf planets, of which Pluto was thought to be the largest. Michael Brown and Emily Schaller of the California Institute of Technology used data collected from the Hubble Space Telescope and the Keck Observatory in Hawaii to determine for the first time that Eris had a greater mass than Pluto.
Eris, discovered in 2005 and named for an ancient Greek goddess of strife and discord, was found to be 27 per cent more massive than Pluto and about half the size of Earth''s moon, Brown said. Pluto, named for the ancient Greek god of the underworld, was discovered in 1930. It was considered our solar system''s ninth planet until August 2006, when the International Astronomical Union declared it a dwarf planet, a term referring to lesser, round solar system bodies orbiting the sun, mostly in an outer region called the Kuiper belt.
Brown, a professor of planetary astronomy in a comment on the study said "I don''t think we''re picking on Pluto. It''s just the truth. Eris is just more massive than Pluto. It''s just the way it is." Scientists previously had figured that Eris''s diameter was bigger than Pluto''s but did not know about mass. Like Pluto, Eris is unlikely to become a holiday destination. Both inhabit a remote and frigid region of the solar system. The new data indicated Eris is likely to be composed of ice and rock, very similar to Pluto. Brown impression of Eris also is that it is covered in an almost perfectly uniform white frost, so making look just like a white billiard ball out there. He explained that Pluto and Eris both follow elliptical rather than circular orbits as they journey around the Sun and that Eris’s orbit is highly elongated and takes 560 years. He added that while Eris ventures anywhere from 3.5 billion miles (5.6 billion km) to 10 billion miles (16 billion km) from Earth, Pluto, whose 250-year orbit on occasion brings it inside the orbit of the outermost planet Neptune, journeys as far as 5 billion miles (8 billion km) from Earth.
Similarly, from the calculations made, the Eris, which has a small moon, was said to have a diameter of 1,500 miles (2400 km), just bigger than Pluto''s 1,400 miles (2,270 km). With roughly 50 known objects in the solar system that can be classified as dwarf planets, including some close in size to Eris and Pluto,Brown said Pluto should be getting accustomed to second place. With only three dwarf planets in the solar system, Pluto is sized in between Eris and Ceres. Although the word planet is used often in astronomy, the term “planet” was not officially defined until 2006. Before the 1990s, only nine planets were known anywhere in the universe. They all reside in our little solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.
The inner planets, Mercury, Venus, Earth, and Mars, were classified as terrestrial planets while, the outer planets, Jupiter, Saturn, Uranus, and Neptune were considered as gaseous planets. Pluto, which at the time was the furthest planet from the Sun, was not included in either group due to its small size and isolated location within the Kuiper Belt—a ring of frozen, rocky objects between the orbit of Neptune and extending past the orbit of Pluto. Pluto stayed a planet because there was really no need to change anything. However, the astronomers began questioning Pluto’s status near the end of the twemany smaller bodies—what are called trans-Neptunian objects—were discovered past the orbit of Neptune. In addition, hundreds of exoplanets (planets orbiting stars other than the Sun) were found to exist, too.
Published: January 27, 2008   
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