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Friday, December 2, 2016

When Meteors Confront a Full Moon

Despite the brightness of our lone natural satellite, observers still may see some of this year's brightest Geminid meteors.

The annual Geminid meteor shower, which peaks the night of December 13 and the morning of the 14th, is typically one of the best of the year. The Geminid shower generally features bright meteors, and, unlike most showers, it’s fairly rich before midnight. Unfortunately, in 2016, the Full Moon occurs in the early evening December 13, something observers will need to keep in mind when planning their viewing.

The Geminids are so named because if you trace all the meteor trails backward, they converge within the boundaries of the constellation Gemini the Twins. This point, called the radiant, lies approximately 3° northwest of the 1st-magnitude star Castor.

Geminid meteors are relatively slow moving, and many leave smoke trails that can last a number of seconds. This year, the shower is active from December 4 to 17. The Geminid meteor shower has a broad peak, so observers normally would see an excellent show all night.

Read full article at http://www.astronomy.com/news/observing/2016/12/when-meteors-confront-a-full-moon
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The Beginning of the End for Cassini

Image of Cassini's final orbits Extended mission solstice orbits (blue) versus  the upcoming ring grazing orbits (tan). NASA / JPL / Cassini
Cassini's final orbits Extended mission solstice orbits (blue) versus the upcoming ring grazing orbits (tan). 
NASA / JPL / Cassini
Cassini's final main engine burn this weekend sets the stage for a stunning grand finale.

After more than a decade exploring the ringed planet and its moons, NASA's Cassini spacecraft is preparing for a daring set of orbits which will set it up for mission's end later next year.

The recent 125th flyby of Saturn's giant moon Titan (T-125) was the prelude to Cassini's final acts, which will play out over the next year. That pass placed Cassini in a high-inclination orbit tilted 60° relative to the ring plane. Cassini will perform 20 passes just 620 miles (1000 kilometers) outside the F ring of Saturn in a phase known as the Ring-Grazing Orbits, which runs from late November 2016 through April 2017.

Cassini already reached apoapse, or its farthest point from Saturn, on Wednesday, November 30th. The first ring crossing is coming right up this weekend on Sunday, December 4th, at 7:09 a.m. EST / 13:09 UT. During the first periapse pass on Sunday, Cassini will also burn its main engine for the 183rd and final time for the mission. All later fine course corrections will be made using thrusters only.

Things get even more interesting after April, when the series of Grand Finale Orbits will begin, taking the spacecraft through the 1240-mile-wide (2000-kilometer-wide) gap between the planet's cloud tops and rings for 22 final orbits. The Grand Finale Orbits start with the spacecraft's 126th and final pass near Titan, which will set the spacecraft up for much tighter final orbits.

Read full article at http://www.skyandtelescope.com/astronomy-news/nasa-cassini-ring-grazing-orbits/
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Thursday, December 1, 2016

4*P Comet Campaign Seeks Imagers Worldwide

Calling all imagers! Three comets will make close flybys of Earth over the next two years. Join a new pro-am effort to make the most of this rare triple play.

Comet 46P/Wirtanen is seen here on February 7, 2008 during its last favorable perihelion passage. On December 16, 2018, the comet will pass just 0.077 A.U. (7.2 million miles) from Earth and may become an easy naked-eye object. Rolando Ligustri.

If you're as crazy about comets as I am, here's an opportunity to make an important contribution to their understanding. The Planetary Science Institute (PSI) is putting out the call to amateurs and professionals alike to make the best of a unique opportunity.

The Planetary Science Institute is a private, nonprofit corporation dedicated to solar system exploration. It's headquartered in Tucson, Arizona, where it was founded in 1972. PSI scientists and educators are involved in everything from space missions to solar system studies, science education, and public outreach.

Three comets — 41P/Tuttle-Giacobini-Kresak, 45P/Honda-Mrkos-Pajdusakova, and 46P/Wirtanen — will all pass Earth at very close distances ranging from 7.4 million to 14 million miles (11.9 to 22.5 million km) within the next two years. Close approaches of three comets within two years are rare and only happen every few decades.
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