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Pluto joined by two "new" members of the dwarf planet club

Wednesday, August 30, 2006

Artist's rendering of Pluto with the Sun in the background

Pluto, formerly known as the ninth planet of our solar system, has been reclassified to a new category called "dwarf planet." The vote by the International Astronomical Union officially upgrades Earth's neighborhood from the traditional nine planets to eleven -- eight classical planets, and three dwarf planets. The eight classical planets of our solar system are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Pluto, Ceres, and 2003 UB313 (temporary name) are the first members of the new "dwarf planet" category.

Clyde Tombaugh at Flagstaff's Lowell Observatory discovered Pluto in 1930. Pluto's designation as a dwarf planet was caused by the new rule, which says a planet must orbit the sun and be large enough to assume a nearly round shape, and must "clear the neighborhood around its orbit." Pluto's oblong orbits overlap Neptune's.

Nevertheless NASA plans to carry on with its New Horizons spacecraft mission, which in January 2006 began a journey to the dwarf planet and its moon, Charon whether Pluto is a planet or not. The seven science instruments on the piano-sized New Horizons probe will shed light on Pluto’s surface properties, geology, interior makeup and atmospheres.

For more information about the IAU ruling, see the IAU 2006 General Assembly: Result of the IAU Resolution votes.

The Meaning of Planet

Wednesday, August 16, 2006

What is a planet? For years, astronomers have been debating that question, with the status of tiny Pluto hanging in the balance. Finally, an answer is in the offing. Today, the International Astronomical Union's Planet Definition Committee announced their proposal for a new, official definition of "planet." If the proposal is approved by a vote of IAU astronomers on August 24th, the number of planets in the Solar System would swell from nine to twelve. And, yes, Pluto would be among them. Get the full story at .

Orion's Inner Beauty

Tuesday, August 15, 2006

Sword of Orion

This infrared image from NASA's Spitzer Space Telescope shows the Orion nebula, our closest massive star-making factory, 1,450 light-years from Earth. The nebula is close enough to appear to the naked eye as a fuzzy star in the sword of the popular hunter constellation.

The nebula itself is located on the lower half of the image, surrounded by a ring of dust. It formed in a cold cloud of gas and dust and contains about 1,000 young stars. These stars illuminate the cloud, creating the beautiful nebulosity, or swirls of material, seen here in infrared.

This image shows infrared light captured by Spitzer's infrared array camera. Light with wavelengths of 8 and 5.8 microns (red and orange) comes mainly from dust that has been heated by starlight. Light of 4.5 microns (green) shows hot gas and dust; and light of 3.6 microns (blue) is from starlight.

Take a look or download Orion's Portrait at medium or high resolution.

Credit: NASA-Spitzer Space Telescope

Universe Might be Bigger and Older than Expected

Thursday, August 10, 2006

A project aiming to create an easier way to measure cosmic distances has instead turned up surprising evidence that our large and ancient universe might be even bigger and older than previously thought.

If accurate, the finding would be difficult to mesh with current thinking about how the universe evolved, one scientist said.

A research team led by Alceste Bonanos at the Carnegie Institution of Washington has found that the Triangulum Galaxy, also known as M33, is about 15 percent farther away from our own Milky Way than previously calculated.

The finding, which will be detailed in an upcoming issue of Astrophysical Journal, suggests that the Hubble constant, a number that measures the expansion rate and age of the universe, is actually 15 percent smaller than other studies have found.

Currently, most astronomers agree that the value of the Hubble constant is about 71 kilometers per second per megaparsec (a megaparsec is 3.2 million light-years). If this value were smaller by 15 percent, then the universe would be older and bigger by this amount as well.

Scientists now estimate the universe to be about 13.7 billion years old (a figure that has seemed firm since 2003, based on measurements of radiation leftover from the Big Bang) and about 156 billion light-years wide.

The new finding implies that the universe is instead about 15.8 billion years old and about 180 billion light-years wide., Ken Than More:Universe Might be Bigger and Older than Expected