Mohawk Valley Astronomical Society

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Planet Watch 2009

by Perry Pezzolanella, MVAS

The International Year of Astronomy 2009 will be a great year to celebrate astronomy with the public as there will be at least one bright planet conveniently visible on every evening of the year. There will also be many beautiful pairings of different planets and planets with the Moon. Predictable meteor showers and orbiting satellites, along with unpredictable comets and auroras, will give children and adults alike a deeper appreciation of the night sky.

Unfortunately there are no lunar or solar eclipses this year. Very careful observers may notice dusky shading on the bottom part of the Full Moon around 9 P.M. on August 5 as the moon undergoes a 30% penumbral eclipse, but it will be brief and subtle. The next total lunar eclipse will be in the wee hours of the morning on December 21, 2010. The next solar eclipse locally will not occur until shortly before sunset on May 20, 2012 when the Sun will hardly be 5% eclipsed at best.

Venus dominates the evening sky at the beginning of 2009, to be replaced by Saturn as soon as the goddess of beauty departs in March. Mercury will appear briefly in the evening sky towards the second half of April. Saturn will fade in the glare of the Sun by the end of July only to be replaced in time by Jupiter, which will command attention through December. When Jupiter begins to descend into the western evening sky in November, Mars will begin to rise earlier and brighter in the east before midnight. Uranus and Neptune are never brilliant, although both are curiosities, and will be visible in the evening from August through next January. Here is the breakdown for each planet in the evening sky during 2009:

Mercury: This rocky world is challenging to find, but will have a beautiful showing in the evening from April 12 to May 6 with Mercury at its highest on April 26. On that evening it will be very easy to locate as it will be at its highest, and coincidentally, below a thin crescent Moon and the Pleiades! Mercury grows steadily larger through this period from 6 to 10 arcseconds across as it approaches Earth; its magnitude will hover around 0. It will go through phases like a tiny, coppery version of the Moon from nearly full to a thin crescent.

Venus: This inferno world will be a beautiful evening star from January until mid-March. Venus will begin the year appearing slightly more than half full and grow into a large, thin crescent by March. The magnitude will increase from -4.3 to -4.6 and its size will grow from 21 arcseconds to nearly one arcminute by late March before moving into the morning sky and then shrinking and fading for the rest of the year. Venus will make several beautiful pairings with the crescent Moon during the year in the evenings and mornings.

Mars: This dusty world will remain small and distant in the morning sky until around November when it will finally start rising by midnight in Cancer. It will grow from 8 arcseconds around Halloween to nearly 13 arcseconds by New Year’s and brighten from magnitude +0.4 to nearly -1 as it nears opposition on January 29, 2010.

Jupiter: This stormy world will perform a class act for the public as it will be nearly at its largest and brightest possible, and this will occur in the balmy summer months to boot. Jupiter is at opposition on August 14 in Capricornus and will be 48.9 arcseconds across and blaze at magnitude -2.9. The huge size will allow for plenty of detailed viewing of Jupiter’s clouds including the Great Red Spot. It should be possible to see the tiny discs of the larger moons, Callisto and Ganymede, and to compare their size to smaller Europa and Io. It might even be possible to detect slight color differences among them. Jupiter will become lost in the evening twilight next January as it fades to magnitude -2.0 and shrinks to 33 arcseconds across.

Saturn: This ringed world goes nearly ringless this year and is beautifully placed for public observing in the warmer spring and early summer evenings. Saturn is at opposition on March 8 in eastern Leo when it will be 19.8 arcseconds across and shine at magnitude +0.5. The rings will be nearly edge-on making it impossible to see any detail within them, but most of the globe will be visible, which is rare because the rings usually obscure a large portion. This will be a good chance to observe any belts or spots. The rings will be exactly edge-on by September, but unfortunately Saturn will be lost in the Sun’s glare. Saturn will slowly fade to magnitude +0.8 and shrink to less than 17 arcseconds across by August when it becomes lost in the evening twilight.

Uranus: This misty world will be at opposition on September 17 in Pisces close to the Aquarius border. Uranus will be 3.7 arcseconds across and shine at magnitude +5.7 not far below the Circlet of Pisces. It continues to display an equatorial view, which may allow for a rare chance to observe belts or spots through larger telescopes such as the 16” Schmidt-Cassegrain at the MVAS Apollo Observatory.

Neptune: This windy world will be easy to find as it will never be far from Jupiter this year. They will be very close in early July and again in mid-December. Neptune is at opposition on August 17 in Capricornus; it will be 2.4 arcseconds across and shine at magnitude +7.8. A finder chart for Uranus and Neptune will appear in the July issue of Telescopic Topics. Both planets will rise before midnight by August and gradually fade into the evening twilight during January 2010.

Pluto: This frozen world will be nearly impossible to find this year as it is in the heart of M24, the Small Sagittarius Star Cloud, which is part of the steam cloud of the Milky Way rising from the spout of the Sagittarius Teapot. Pluto is at opposition on June 23 and will shine feebly among millions of stars at magnitude +13.9 being nothing more that a star-like spark at 0.1 arcseconds across. Locating Pluto will get easier in the years ahead as it leaves the Milky Way and ends up in the Sagittarius Teaspoon by 2015, the same year that the New Horizons spacecraft flies past it.