By David A. Huestis
I can’t believe I’m writing about astronomical events for December already. Where did 2016 go? Time is flying by so fast that I often feel like I’ve gotten caught in the wake of someone’s time machine, propelling me into the future. But more likely it is an inverse square function of age. Just substitute time for distance in the equation. The older one gets the faster time seems to pass. How many of you can relate to that declaration?
Usually my December column highlights the best meteor shower of the year — the Geminids. Unfortunately the peak of this shower on the night of December 13-14 coincides with the Full Moon this year. While the Geminids are fairly bright and also have a reputation for producing exploding meteors called fireballs, the region of the sky from where the meteors appear to radiate is near Gemini’s brightest stars, Castor and Pollux. Regrettably the brilliant Moon will be in the neighboring constellation Taurus.
While you may still catch a glimpse of a couple of Geminids as they enter our atmosphere at 21.75 miles per second, we’ll be lucky to see a handful of the normal 60+ meteors per hour. If the skies remain clear you could take a few minutes to see if any bright meteors overcome the Moon’s brilliance. Otherwise you can wait until the Quadrantids on January 3-4.
On the evening of December 2 just after sunset take a look towards the western sky. A waxing crescent Moon will be just less than ten degrees to the right of brilliant Venus. On the following evening the Moon will be directly above Venus and separated by about six degrees. Send an image of this beautiful sky scene to me at email@example.com.
Four days later an interesting occultation occurs. As the Moon slides eastward (12 degrees per day) across the sky, it often passes in front of bright stars and planets. During the late afternoon of the 6th our solar system’s outer most distant planet Neptune will be occulted by the First Quarter Moon. A telescope is required to view this event. Unfortunately from here the disappearance of Neptune behind the Moon’s dark limb/edge (left) at around 4:15 p.m. will not be seen as the Sun will be setting at the same time. The sky will be too bright to discern Neptune. However, when Neptune reappears along the bright limb of the Moon at around 5:35 p.m. telescopic observers will be able watch its return. Neptune is faint and small, but you will be able to determine you’ve seen this distant world because of its blue-green hue. This occultation is well-placed in the sky with the event occurring about 40 degrees above the southern horizon.
Have you ever seen the planet Mercury? During the first three weeks of December you can find the solar system’s inner most planet low in the western sky after sunset. At mid-month Mercury will be at its highest position above the horizon, just less than seven degrees. A fist held at arm’s length covers ten degrees in the sky. So you’ll require a decent treeless view towards the southwestern sky. After mid-month Mercury will quickly sink back towards the horizon and eventually disappear into a bright twilight sky. Its conjunction with the Sun is on the 28th.
The Moon has occulted Taurus the Bull’s bright star Aldebaran several times this year. And we have another such event visible on the night of December 12, beginning just before midnight in southern New England. At approximately 11:17 p.m. the dark limb (left side) of a waxing gibbous Moon will occult (pass in front of) Aldebaran, For about one hour and fourteen minutes the star will remain hidden behind the Moon. At approximately 12:31 a.m. Aldebaran will emerge along the Moon’s bright limb (right side). Occultations by the Moon are always fascinating to watch, as one can often see the occulted object blinking in and out from behind lunar mountains or crater rims.
Furthermore, don’t forget that the Winter solstice begins at 5:44 a.m. on the 21st. Notice how low an arc the Sun travels across the sky. After this date and time the Sun’s arc will rise higher and higher each day as it appears to travel northward in our sky, reaching the Vernal Equinox (Spring) on March 20, 2017. The apparent shift of the Sun’s position in the sky is the result of the Earth’s fixed axial tilt of 23.5 degrees as it revolves around the Sun. See my column Reason for the Seasons (http://www.theskyscrapers.org/reason-for-the-seasons) to refresh your knowledge on this topic.
Also, as we approach the holiday season, many folks ask me about the mystery of the Christmas Star. An unabridged version of my latest treatise on this topic can be found on the Skyscrapers website http://www.theskyscrapers.org/mystery-of-the-christmas-star for your examination.
As I write this column early in November, once again we have had temperatures well above normal. However, winter will soon be upon us and colder weather patterns may blanket the area with snow. But as long as grounds at the local Rhode Island observatories are accessible, the telescopes will be available for you to explore “deep sky” objects within the brightest constellations of the night sky. Knowledgeable sky interpreters will be on hand to introduce you to a variety of celestial wonders. Be sure to visit each website prior to setting out for a field trip to these facilities, as wintry conditions can force unexpected closures.
Seagrave Memorial Observatory (http:/www.theskyscrapers.org) in North Scituate is open to the public every clear Saturday night. However, in December Seagrave will only be open on the 3rd and 17th. Ladd Observatory (http://www.brown.edu/Departments/Physics/Ladd/) in Providence is open every clear Tuesday night. The Margaret M. Jacoby Observatory at the CCRI Knight Campus in Warwick (http://www.ccri.edu/physics/observatory.htm) is open every clear Wednesday night. Frosty Drew Observatory (http://www.frostydrew.org/) in Charlestown is open every clear Friday night year-round.
Great American Total Solar Eclipse on August 21, 2017. Countdown: 262 days as of December 1, 2016.
Happy holidays and clear skies to all.