Vesta, the vestige of a distant past

The following sun and moon data for Oct. 30, 2008 is provided by the United States Naval Observatory.

Sunrise: 7:31 a.m.

Sunset: 6:12 p.m.

Moonrise: 9:22 a.m.

Moonset: 6:57 p.m.

Moon phase: The moon is waxing crescent with 3 percent of the visible disk illuminated.

The asteroid Vesta reached opposition Oct. 28, and Pagosa Country’s dark skies and a thin, waxing crescent moon make it a prime time for tenacious stargazers to attempt locating the object.

Stargazers will find the asteroid rising at sunset in the constellation Cetus.

Although Vesta whizzes across our night sky at the naked-eye visibility limit of magnitude 6.4, stargazers will find binoculars — or a telescope — and a starchart of Cetus and Pisces useful in their search. Once located, stargazers can follow the asteroid’s trajectory through the constellations during November and December.

From its discovery in 1807 until 1845, Vesta was classified as a planet. However, continued observation indicated Vesta wasn’t planetary in its behavior, and professional astronomers concluded Vesta was an asteroid: Although in 2011 that classification may change again with the visit of NASA’s Dawn probe.

With a diameter of 311 miles and a surface geology similar to that of Earth and Mars, Vesta may be a strong candidate for reclassification as a dwarf planet.

For example, Hubble Space Telescope observations reveal a diverse world on Vesta. With an exposed mantle, mineralogical variations across Vesta’s surface, ancient lava flows and impact basins, Vesta speaks to conditions and processes present during the early formation of our solar system. In addition, though only 325 miles across — about the length of Arizona — observations indicate the asteroid once had a molten interior.

While evidence of volcanism has scientists intrigued, Vesta also has a unique surface feature that scientists are keen to peer into. At the asteroid’s south pole is a giant crater 285 miles across and 8 miles deep. Scientists estimate the massive collision that created the crater gouged out one percent of the asteroid’s volume, blasting over one-half million cubic miles of rock into space.

“The Hubble observations show that Vesta is far more interesting than simply a chunk of rock in space as most asteroids are,” said Ben Zellner of Georgia Southern University in a press release.

Zellner and his colleagues say Vesta offers new clues to the origin and evolution of our solar system and the interior makeup of the rocky planets.

“Vesta has survived essentially intact since the formation of the planets,” Zellner said. “It provides a record of the long and complex evolution of our solar system.”

Hence, NASA’s September 2007 launch of the Dawn probe.

Using a visible light camera, a visible and infrared mapping spectrometer and a gamma ray and neutron spectrometer, Dawn will study Vesta in order to provide scientists with data that will create a clearer picture of the early evolution of our solar system.

Once it’s mission at Vesta is complete, Dawn will continue on to the dwarf planet Ceres.

Dawn is scheduled to arrive at Vesta in August 2011.

james@pagosasun.com


Photo courtesy NASA
In this gorgeous skyscape, gas giant Jupiter along with the stars and cosmic dust clouds of the Milky Way hang over the southern horizon in the early morning hours as seen from Stagecoach, Colo. Jupiter is the brightest object near picture center. Along with the stunning Milky Way, Jupiter is hard to miss, but a careful inspection of the view also reveals main belt asteroid Vesta. Of all the asteroids, Vesta is the brightest and is now just bright enough to be visible to the naked eye from locations with very dark, clear skies. Vesta appears relatively bright now because it is near opposition, literally opposite the Sun in planet Earth’s sky and closest to Earth in its orbit.