December 2007
Skywatcher’s Guide for December 2007
PLANETS
MARS CLOSEST TO EARTH UNTIL YEAR 2016
Mars starts December 2007 at 57.4 million miles away from Earth. By December 18, Earth closes to only 54.8 million miles from the Red Planet, the closest Mars will be to the Earth until the year 2016. This is six days before its opposition date (Dec. 24), when Mars is opposite from the Sun in the sky. On December 18 until after its opposition date, Mars shines at a very bright magnitude -1.6 (brighter than Sirius, the brightest star in our night sky) and will appear almost 15.9 arc seconds in diameter in a telescope (large enough to see surface contrast features in small amateur telescopes). However, on December 18 Mars does not rise above 40 degrees in altitude until 9:10 p.m. (40 degrees in altitude is high enough in the sky for typical sharp telescopic viewing; the higher the altitude, the less air is being looked through). For this reason (and because Mars shrinks only slightly in early January), observers can take advantage of more convenient evening telescopic viewing later in December and in January when Mars is higher up, earlier at night.
Mars should be viewed in a telescope when it is high in the sky. In early December observers should start a viewing session at around 9:30 p.m. or view at any time in the late night hours (when Mars is highest overhead). In middle December, an observer should start observing Mars at around 8:30 p.m. Around its opposition on Dec. 24, Mars is visible all night long, as it rises at sunset and is overhead around midnight. Best views of any planet should be when it is highest in the sky, but viewing is dependent on atmospheric stability and conditions, and of course, the quality and size of the telescope used. Large, high quality amateur telescopes in good “seeing” (stable atmospheric conditions) will best reveal any features on the Martian disk.
Mars is highest in the sky this month at around 2:30 a.m. in early December, at 1:15 a.m. in middle December and by 11:45 p.m. in late December. When highest in the sky this year into January the Red Planet “transits” the meridian (the north/south line in the sky) at 84 degrees in altitude for southern Arizona. This is much higher than Mars reached in August during its record close apparition that year and higher than in 2005. Even though Mars will be significantly smaller this year than in 2003, its placement overhead should offer sharper telescopic viewing, especially for desert Southwest observers. Observers should also note that the southern and northern polar caps may more easily seen than in 2003 or 2005, as they face equally towards Earth.
Mars can be first seen when it rises above the east-northeastern horizon by around 7:15-7:30 p.m. in the early December twilight. All month long Mars is not far from the Gemini twin stars, Castor and Pollux. The Red Planet is in retrograde or reverse motion during December into January. Also, look for the full Moon (the ‘Moon Before Yule’) to rise very near Mars in our sky this month in the east on the evening of Sunday, December 23. Mars will be only 0.15 arc minutes from the edge of the Moon’s disk that evening and the Moon covers or ‘occults’ Mars that evening from Alaska and northern Canada (and much later at night for eastern Europe).
To help the public learn about this apparition of Mars (and assist them in viewing it), Flandrau Science Center will offer special presentations on Mars and current exploration associated with The Phoenix Mars Mission (The University of Arizona lead mission to the Martian arctic). Flandrau will host four special events on Fridays and Saturdays on December 14/15, 2007 and January 4/5, 2008.
- Special free telescope viewing (weather permitting) on the UA mall will be held from 6:30 until 10 p.m. all four nights.
- At 8:00 p.m. each night, come see special live planetarium presentations on Mars by University of Arizona researchers associated with The Phoenix Mars Mission, set to land on the north pole of Mars in May of 2008.
Each presentation will involve a special area of research associated with The Phoenix Mars Mission, led by The University of Arizona, the first public university to lead a mission to another planet. Click here for more information on Mars viewing and special presentations.
Finally, it’s possible a Mars hoax e-mail might still be found making its way around the Internet, stating that Mars will be closest to the Earth in 60,000 years. Please go to our news story for more information.
Bright Jupiter is moving into the glare of the Sun near the southwestern horizon during evening twilight. It may be lost to view to the unaided eye by December 4/5. Jupiter is now in Sagittarius the Archer and is found from southernmost states 45 minutes to 1 hour after sunset, very low in the southwestern evening sky.
Saturn has left its dramatic grouping with Venus, but is still near (eight degrees from) the bright star Regulus in the constellation Leo, the Lion. Saturn appears as a closer to first magnitude star-like object (at magnitude 0.8), and is dimmer this year because its rings are more edge-on. Saturn continues to gain altitude while Venus will slowly sink out of view in early 2008. Saturn rises earlier each morning and is very high overhead at dawn by the start of the month. By December 31 Saturn rises at around 10 p.m. above the eastern horizon. The last quarter Moon rises along with and close to Saturn in our sky, around midnight on Saturday morning, December 1.
The brilliant planet Venus remains our ‘morning star’ this month in the east but loses altitude in our morning sky. Even so Venus rises over 3 hours before the Sun by the end of the month. Venus is around 20 degrees in altitude above the eastern horizon about 75 minutes before sunrise (around 6 a.m. mid-month for southern Arizona). As Venus is now receding from Earth it continues to shrink in apparent size in a telescope, and now appears in a gibbous phase. To the unaided eye Venus appears as an intensely bright white star that does not twinkle. All month long Earth’s sister planet is found well up above the eastern horizon, 90 to 45 minutes before sunrise. Also, the waning crescent Moon is grouped near Venus on Wednesday morning, December 5.
Mercury is currently lost in the glare of the Sun and not visible to the naked eye from the northern hemisphere.
Visitors to Flandrau’s 16-inch telescope should note that due to building obstructions on the University of Arizona campus, Mars will only start to be visible in the telescope by 9:45 p.m. on December 7. Mars will be visible earlier in the telescope each night, so that by Dec. 14 it can be seen by 9 p.m. Other celestial objects as well will be shown, weather permitting. Flandrau’s main exhibit hall and planetarium are now closed on Wednesdays but the telescope remains open, weather permitting Wednesday through Saturday nights (excluding select holidays). The telescope normally closes at 10 p.m.
Finally, remember that in spotting planets there is a general rule: ’stars twinkle, planets don’t’. This is because stars are point sources of light; therefore starlight is easily disturbed and shifted by air currents in the Earth’s atmosphere.
GEMINID METEOR SHOWER PEAKS ON DECEMBER 13!
Special Presentation at Flandrau on December 13
 This sky chart shows the eastern sky at 8:45 p.m. on Dec. 13 (MST) from the Desert Southwest. |
On December 13-14 (Thursday night into Friday morning), the bright Geminid meteor shower is at its best, from late evening until first light of dawn. The moon is a thin waxing crescent, and sets just after 9:00 p.m. on the 13th, making it a great year for viewing this major meteor shower! The Geminids are considered one of the best meteor showers of the year, and should be much more impressive than this year’s Leonid shower. Stargazers can start viewing by 8 p.m. or 9 p.m. to see this major meteor shower, which lasts all night long. Conversely, early rises can simply get up at 4 or 5 a.m. to catch some shooting stars before sunrise. If you see a bright Geminid meteor, you should be able to trace its path backward to a point in the sky near Castor and Pollux, the Gemini twins. To see the shower simply look high in the eastern and northern sky and overhead after 8 p.m. Expect to see upwards of 50 meteors per hour in a clear, dark sky away from city lights, into the late night hours. Dark viewing locations are still highly recommended: glare from artificial light sources will certainly reduce the amount of meteors seen.
To help the public learn about this meteor shower (and assist them in viewing it), Flandrau Science Center will offer a special presentation on Thursday night, December 13, at 8:00 p.m. on the Geminid meteors (and about meteor showers in general) by Dr. Larry Lebofsky. Dr. Lebofsky, now recently retired, was for many years a Senior Research Scientist and Lecturer in Astronomy at the Lunar & Planetary Laboratory. He continues to teach at The University of Arizona. For more information on how best to see this meteor shower and this talk see our news story.
Comet Holmes still visible but growing fainter
Previously small, faint Comet Holmes (designation 17P) surprised astronomy observers around the globe by outbursting and suddenly becoming bright enough (at a visual magnitude rating of 2.5) to see with the naked eye on October 25. Click here for our news story to learn more.
DECEMBER STARS
In late December and early January look in the east for the bright stars of winter to rise around 8 p.m. Orange Betelgeuse, the shoulder of Orion the Hunter, shines left of Orion’s 3 glittering belt stars. The Gemini Twins, the bright stars Castor and the slightly brighter Pollux, twinkle left of Orion. An hour later, by 9 p.m., the bright star Procyon (whose name means “Before the Dog”) is newly risen in the east. From Tucson’s latitude, the Dog, – that is the “Dog Star” Sirius– the brightest star in all the heavens, rises almost at the same time as Procyon, so Procyon’s name isn’t so true this far south. Once it rises, brilliant Sirius will dramatically flicker different colors when low in the sky, making for a wonderful sight to the naked eye and in binoculars; such flickering is due to earth’s atmosphere.
Leaving center stage and moving to the western half of the sky in December is the Great Square of Pegasus. Find the Great Square (before 8 p.m. in early to middle December) quite a ways up from Fomalhaut, the bright star marking the Southern Fish (Pisces Austrinus), which lies low in the southwest. In December the Great Square can also be found all month long (before 10 p.m.) by facing west and looking far above and left (or southwest in this instance) of the bright star Deneb. At 10 p.m. Deneb, the brightest star of Cygnus, the Swan (whose other name is the Northern Cross), will lie above the northwestern horizon. The eastern corner star of the “Great Square” of Pegasus, Alpheratz, is actually also the head of Andromeda, the Chained Lady or Princess. In Andromeda, is the “Great Andromeda Galaxy”, M31, which can be viewed as a fuzzy spot in binoculars. High overhead (and far from M31) is the Seven Sisters (or Pleiades) star cluster, a wonderful sight in binoculars.
Winter’s Solstice on Friday, December 21 (Dec. 22 for eastern North America)
Days become shorter in the fall due to the lower altitude of the sun in the Northern Hemisphere sky. The shortest day for the Northern Hemisphere is always on the Winter’s Solstice, which this year officially begins at 11:10 p.m. MST or Tucson time on Friday December 21. From this time forward the sun now gains altitude in our Northern Hemisphere sky as winter now begins for the Northern Hemisphere (and summer for the Southern Hemisphere). Also, although the 21st marks the shortest day, the earliest sunset occurs on December 7th (for much of the Northern Hemisphere). The discrepancy between shortest day and earliest sunset is due to the use of average or ‘mean time’ across times zones. Because of time zone changes, the solstice (at 6:10 Universal Time) occurs on Dec. 22 for the Eastern time zone, and areas east through Europe into Asia.
MOON PHASES
December 2007 has two last quarter Moons: The first will occur on Saturday morning, December 1st and the second on Monday morning December 31st. The December new moon occurs on December 9. The December first quarter Moon will occur on Sunday evening, December 16th. The Full Moon Before Yule rises close to Mars in the Northern Hemisphere sky on the evening of Sunday, December 23 and sets on the morning of December 24 (The Moon occults or covers Mars as seen in far northern regions, such as Alaska, northwestern Canada and northeastern Europe, including Scotland).
Note:Additional information can be accessed by phone at Flandrau Science Center’s Astronomy Newsline at (520) 621-4310 or as a menu option at 621-S-T-A-R.
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