Jimmy Westlake: Moons, asteroids and comets
August 4, 2011
Steamboat Springs — Moons, asteroids and comets may be the little guys in our solar system, but they've been making some big news lately.
By the latest reckoning, there are 13 planets and dwarf planets in our solar system and between them they own 171 moons. That's an average of 13.1 moons per planet. Boy, did the Earth get shortchanged Even the dwarf planet Pluto has more moons than Earth.
Recently, astronomers using the Hubble Space Telescope spied a previously unknown moon of Pluto's, bringing its total to four. Their names are Charon, Nix, Hydra and P4. Co-discoverers Mark Showalter and Douglas Hamilton would like to name P4 "Cerberus," but that proposal must await approval by the International Astronomical Union (IAU), the body responsible for naming new objects in the solar system.
Astronomers theorize that the only way a planet as tiny as Pluto could play host to a family of four moons is if a colossal impact long ago shattered Pluto and the resulting fragments now orbit it. A similar hypothesis has been proposed for the origin of Earth's moon. Knowing the whereabouts of all of Pluto's moons is of vital interest because the New Horizons spacecraft will shoot through the Pluto system in July 2015 at a speed of more than 30,000 mph. An uncharted moon in the wrong spot could spell curtains for the mission.
The solar system's brightest and second largest asteroid, Vesta, is currently being studied by the Dawn spacecraft, which successfully achieved orbit around Vesta last month. Vesta is about as bright as it can ever be this week in our evening sky as it reaches its closest point to Earth on Friday. It is barely visible to the unaided eye from dark sky locations in the constellation Capricornus. Check out the NASA website http://dawn.jpl.nasa.gov/ for finder charts and the latest close-up images of Vesta.
Finally, there is a little comet zipping through our summer skies this month — Comet Garradd C/2009P1. Discovered by Australian astronomer Gordon Garradd in 2009, this icy interloper is a binocular object near the star Enif in the constellation Pegasus. Later this year, Comet Garradd might barely reach naked-eye brightness, but it should remain an easy binocular object throughout the summer and fall. Even now, the little fuzz ball is sporting a short, stubby tail as it nears the sun.
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Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. He is an avid astronomer whose photographs and articles have been published all around the world. Check out Jimmy's website at http://www.jwestlake.com.