technologyvista.in: What Is a Planet? While many people can point to a picture of Jupiter or Saturn and call it a planet, the definition of this word is much more subtle and has changed over time. Astronomers decided on a new definition in 2006 after the discovery of several worlds at the fringes of the solar system. The International Astronomical Union defined a planet as an object that: orbits the sun has sufficient mass to be round, or nearly round is not a satellite (moon) of another object has removed debris and small objects from the area around its orbit The IAU also created a new classification, dwarf planet, which is an object that meets planetary criteria except that it has not cleared debris from its orbital neighborhood. This definition meant that Pluto — considered a planet at the time — was demoted and reclassified as a dwarf planet. The term planet originally comes from the Greek word for wanderer. Many ancient cultures observed these moving stars, but it wasnt until the advent of the telescope in the 1600s that astronomers were able to look at them in more detail. Small telescopes revealed moons circling Jupiter — a big surprise to Galileo Galilei (the likely discoverer) and his opponents at the Catholic Church — as well as rings around Saturn and an ice cap on Mars. Telescopes also revealed the existence of objects not known to the ancients, because they are too far away and small to be spotted with the naked eye. Uranus was found on March 13, 1781, by the prolific astronomer William Herschel. Ceres was discovered between Mars and Jupiter in 1801. It was originally classified as a planet, but it was later realized that Ceres was the first of a class of objects eventually called asteroids. Neptune was discovered in 1846. [Related: Solar System Planets: Order of the 8 (or 9) Planets] Astronomers continued scouring the solar systems outer reaches in search of a large Planet X that was believed to be disturbing the orbits of Uranus and Neptune. While these irregularities were later discounted by further observations, Clyde Tombaugh did spot a smaller object in 1930 beyond the orbit of Neptune. Called Pluto, the object (then called a planet) was relatively small and had a highly eccentric orbit that sometimes even brought it closer to the sun than Neptune is. Discovery of more worlds Nothing close to Plutos size was found in the solar system for more than two generations. That changed in the 2000s, when Mike Brown — a young astronomer at the California Institute of Technology — was in search of a defining research project and decided upon searches for objects in the outer solar system. In quick succession, Brown and his team discovered several large trans-Neptunian objects, or icy bodies beyond Neptunes orbit. While discovering icy objects that far away was not unexpected — the supposed Oort Cloud, the birthplace of comets, should have trillions of these things — it was the size that made other astronomers pay attention. Some of Browns notable discoveries included Quaoar; Sedna; Haumea; Eris and its moon, Dysnomia; and Makemake. All were found in a relatively short period of time, between 2001 and 2005. Eris (which was originally nicknamed Xena after a popular television show of the time) was large enough that some in the media were calling it the 10th planet. Source : bit.ly/1lIjctI
Posted on: Sat, 24 May 2014 04:30:00 +0000
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