Jimmy Westlake: Pluto: The dot becomes a world
Steamboat Springs — NASA’s New Horizons spacecraft, after a nine-year, 3 billion-mile journey, is poised to fly past Pluto this summer and reveal to us, at long last, the mysteries of this misfit planet and its five known moons.
Kansas farm boy Clyde Tombaugh was hired as a research assistant at the Lowell Observatory in Flagstaff, Arizona, in 1929 at the age of 23. His job was to pick up the search for Planet X after famed astronomer Percival Lowell had passed away.
Within a year, Tombaugh had made the discovery that would make him world famous. The discovery of Planet X was announced on March 13, 1930, Percival Lowell’s birthday.
The Lowell Observatory solicited names for the new planet from the public and, from all those submitted, chose the name sent in by 11-year-old Venetia Burney — Pluto.
Pluto was the name of the Roman god of the underworld, which seemed appropriate for such a cold, dim, far-flung planet. In addition, the first two letters were the initials of the man who initiated the search for Planet X, Percival Lowell. Pluto was welcomed into the family of planets, where it remained for the next 76 years.
Almost immediately after its discovery, Pluto was found to be a misfit planet. Its orbit is so eccentric that, when closest to the sun, it crosses inside of Neptune’s orbit. Its orbit also is tilted 17 degrees out of the plane of the solar system, much more than any other planet.
Initial estimates of Pluto’s mass ran as high as seven times Earth’s mass — a planet in anybody’s book. But, telescopes and observing techniques improved over the passing decades and estimates of Pluto’s mass continually decreased. Astronomers began to joke that if Pluto’s mass kept shrinking at that rate, it would completely disappear by the year 1969.
The big break came in 1978 when astronomer James Christy discovered a large moon orbiting Pluto, a moon that he named Charon. Charon allowed astronomers, for the first time, to accurately measure Pluto’s mass. To almost everyone’s surprise, Pluto’s mass turned out to be only 1/500th that of Earth, much smaller, even, than the moon.
Almost overnight, Pluto’s status as one of the major planets came into question. Tombaugh resisted the rising tide against Pluto up until his death in 1997. Pluto had lost its biggest advocate.
Meanwhile, the search for other trans-Neptunian planets was turning up dozens of other Pluto-like objects in a region that became known as the Kuiper Belt.
When astronomer Mike Brown discovered a distant world in 2005 that outsized Pluto, he wanted to announce it as the planet No. 10, but the International Astronomical Union threw up a big stop sign. The IAU voted in 2006 to redefine the term planet such that Pluto and Mike Brown’s new planet, Eris, did not made the cut. Both were designated as dwarf planets, along with three other solar system mini-worlds: Ceres, Haumea, and Makemake.
The New Horizons spacecraft was already seven months into its journey as “the first spacecraft to the last planet” when Pluto was demoted by the IAU.
Earlier this month, New Horizons was awakened from hibernation to prepare for its July 14 encounter with Pluto. In February, its primary science mission will begin, as Pluto looms ever larger in its sights. By May, New Horizons’ cameras will be sending back images of Pluto that surpass those of our best eye in the sky, the Hubble Space Telescope.
On July 14, New Horizons will skim only 8,500 miles above Pluto’s surface, traveling at a speed of over 8 miles per second. Pluto, a faint dot in earthbound telescopes, will become a world in full detail on our TV screens. Earth’s first emissary to Pluto will have arrived, carrying onboard a small vial of the cremated remains of the Kansas farm boy who first spotted Pluto 85 years ago.
The Colorado Mountain College SKY Club is very pleased to host Dr. Fran Bagenal, an astrophysical and planetary scientist from the University of Colorado and a scientist working closely on NASA’s New Horizons mission, for a free public program at 7 p.m. Wednesday in the Allbright Family Auditorium.
Dr. Bagenal will present an overview of the New Horizons mission and a preview of what we hope to learn when it arrives this summer. A drawing for door prizes and, weather permitting, telescopic observing of the moon and Jupiter will follow the program. Everyone is welcomed to attend.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. His “Celestial News” column appears weekly in the Steamboat Today newspaper and his “Cosmic Moment” radio spots can be heard on local radio station KFMU. Check out Jimmy’s astrophotography website at http://www.jwestlake.com.
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