The final mornings of 2010 (during Dec. 30 and 31) will feature the waning crescent moon with the planets Mercury, Venus and Saturn in the eastern sky before sunrise.
Depending on where you live worldwide, Venus and the moon will rise above the eastern horizon some 3 to 4 hours before sunrise, to light up the wee morning hours until daybreak. For Philippine observers, the screenshot from Stellarium above shows that the Moon – Venus separation is ~20 degrees on December 30, 2010. During this time, the moon will also be ~20 degrees below Saturn. The bright stars Spica in Virgo and Arcturus in Bootes could also be found within this celestial grouping.
Venus is very bright and easy to find. If you look at Venus with a telescope before dawn, you’ll see this planet shining as a wide waxing crescent.
By December 31, the moon and Venus will shine nearly side by side with only 10 degrees of angular separation. Also on this date, Mercury which was in evening dusk during early December will now be in the predawn sky, closer to the horizon. In the screenshot above, it was ~8 degrees above the horizon and ~25 degrees away from Venus. December 2010 provides you with the unique opportunity to catch Mercury in both the evening and morning sky in a single month. Using binoculars will help you see this tiny planet.
Clear skies to all! 🙂
Note: The general rule amateur astronomers use is that the width of your fist from top to bottom held at arm’s length equals about 10 degrees. Read more about this here.
A total lunar eclipse, meteor showers, and the Winter Solstice are the highlights of this month’s stargazing. 🙂
|Dec. 1||Moon at perigree (nearest distance to earth)|
|Dec. 1-4||Catch Venus, Saturn, Spica and the Crescent Moon in a celestial grouping during the predawn sky. Best time to observe will be an hour or two before sunrise. The star Arcturus could also be found just about 30 degrees away in the northeast.|
|Dec. 1-8||Dark Matter Awareness Week|
|Dec. 2||Mercury at Greatest Eastern Elongation (21 deg.)|
|Dec. 4||Venus at greatest illuminated extent. Check eastern sky a few hours before sunrise.This morning Venus will be at its most brilliant, exposing the largest area of sunlit clouds of the current apparition. Two things are going on. The illuminated crescent of Venus is getting larger, percentage wise, as the planet moves towards full sunshine. At the same time, Venus is receding from the Earth, and so getting smaller in diameter. On this date the two balance out, giving Venus its greatest illuminated extent, and making it appear at its brightest, magnitude –4.9.|
|Dec. 7||Mercury is 1.8° south of the thin crescent Moon. Check the western sky a few minutes after sunset. A pair of binoculars would help you see these two objects better.|
|Dec. 10||Monocerotid Meteor Shower|
|Dec. 10||Chi Orionid Meteors|
|Dec. 11||The nearly first-quarter Moon this evening forms a roughly equilateral triangle with bright Jupiter to its upper left and Fomalhaut to its lower left.|
|Dec. 13||A twilight challenge! Mercury and Mars appear closest, 1° apart, very low in the southwest after sunset. A pair of binoculars would help you see these two objects better.|
|Dec. 13-14||Jupiter and Uranus just 10 degrees away from the First Quarter Moon|
|Dec. 13-14||Geminid Meteor Shower|
|Dec. 19||Moon near Pleiades Open Star Cluster in Taurus|
|Dec. 20||Delta Arietid Meteors|
|Dec. 20||Mercury in Inferior Conjunction|
|Dec. 21||Total Lunar Eclipse*|
|Dec. 21||Winter Solstice (23:38 UT)|
|Dec.22||Ursid Meteor Shower|
|Dec. 25||Moon at Perigree|
|Dec. 30 -31||Moon and the Predawn Planets|
|Dec. 31||Jupiter and Uranus less than 0.5 degrees of each other|
*Total Lunar Eclipse
A Total Lunar Eclipse will darken the Moon on December 21. The entire event will be visible from North America with areas to the east, such as South America, Europe, and western Africa, catching the eclipse during Moonset and areas to the west, such as Australia and eastern and northern Asia, seeing the event at Moonrise. Only southern and eastern Africa, the Middle East and India and surrounding countries will miss out on the eclipse entirely. The limb of the Moon begins to fall into the dark shadow of Earth at Dec. 21 6:32 a.m. UTC. The total stage, when the Moon is completely within Earth’s shadow, lasts for approximately 73 minutes, from 5:40 a.m. to 8:53 a.m. UT. During totality, the Moon can take on strange shades, from orange to red to violet, depending on the particulates in the atmosphere at different locations. The event is over by 10:02 a.m. UT.
A total lunar eclipse happens when the moon is full and passes exactly through the line connecting the Earth and the sun.
For Philippine observers, this event will be witnessed as a Partial Lunar Eclipse at moonrise. In Manila, the moon will rise at 5:36 P.M. on December 21 and will set at 6:57 A.M. on 22 December. The major phases of the eclipse are as follows:
|Penumbral eclipse begins||1:29 PM (PST)|
|Partial eclipse begins||2:32 PM (PST)|
|Greatest eclipse||4:16 PM (PST)|
|Partial eclipse ends||6:01 PM (PST)|
|Penumbral eclipse ends||7:04 PM (PST)|
Lunar eclipses are safe to watch and observers need not use any kind of protective filters for the eyes. A pair of binocular will help magnify the view and will make the red coloration of the Moon brighter.
The Sun will reach the Winter Solstice on December 22 at 7:38 a.m. PST (23:38 UT). This marks the time when the Sun lies at its farthest point south of the equator. It signals the onset of winter in the Northern Hemisphere and summer in the Southern Hemisphere. Nights in the Philippines will be longer than daytime. Earth has now completed another annual circuit around the Sun.
The 2010 Geminid Meteor Shower
The Geminids is described by the International Meteor Organization (IMO) as “one of the finest, and probably the most reliable, of the major annual showers presently observable”, and this year’s shower is set to put on a good show. This shower is known to produce colorful bright fireballs that often leaves smoky trails along its way. (For those enthusiast meteor observer, you can report your observation using the methods and report forms at the IMO’s site. You can also read the IMO’s rather technical summary of the 2010 Geminids from there.) It spans from December 7 – 15 and peaks the evening of December 13-14.
Meteors or “falling stars” can be seen at an average rate of sixty meteors per hour under a dark and cloudless sky which the Quarter Moon set just after midnight. If you trace the paths of all the Geminid meteors backward, they appear to radiate from the same point in front of Gemini. This point is called the meteor shower radiant, and is located near the star Castor. But you don’t have to find the meteor shower radiant to see the Geminid meteors, for these meteors shoot all over the sky.
The zenithal hourly rate (ZHR) is the number of meteors that a single observer would see per hour if the radiant were at the zenith and +6.5 magnitude stars were visible. For your count to be corrected to this standard, note your naked-eye limiting magnitude for stars in the part of the sky you are watching. Record the beginning and end times of each of your observing periods to the minute.
All the other known meteor showers were believed to have been produced by debris left behind by comets, but the asteroid 3200 Phaethon is probably the parent of the Geminid meteor shower.
Also during the same night, watch out for Jupiter and Uranus near the Moon before they set after midnight.
Other Meteor Showers for December
Observe when the moon does not interfere and attempt to observe AFTER midnight for most meteors to be seen!
MONOCEROTID meteors – A fair year to explore this minor meteor shower, since the nearly first quarter moon will hamper observations early in the evening during its mid-peak on Dec. 10. However observations in the later hours of the night should reveal several more of these elusive meteors. Look for these meteors as early as December 1 and lasting through the 17th. They emanate very close to the Gemini-Monoceros border, rising in the SE sky at dark local time and overhead/south about 1:00 a.m., very favorable for both southern and northern hemisphere observers but attempt to observe when the moon is not in the sky. In some years up to a dozen meteors per hour can be seen from this shower; the point of radiant is: RA 06h 50m; DEC +10d.
CHI ORIONID meteors – like the Moncerotid meteors that peak on the same night, the light from the moon will hamper observations until moonset just before midnight. It is very interesting that the Monocerotid and this shower both peak at nearly the same night….as its name implies,the CHI ORIONID stream has its radiant very near that fairly bright star, and thus the shower members from both showers are hard to differentiate many times; even more interesting is that the Chi Orionid meteors have TWO radiants apparently, one very close to the “horns of the bull” in Taurus and the other further into the constellation of Orion.
DELTA ARIETID meteors – If you want one early in the evening, this is IT!; look for about 10 meteors per hour (the moon this year will be a full one during this meteor shower, so only the brightest of these should be seen this year) coming from the tiny constellation of Aries. Overall a poor year for this minor shower.
URSID METEORS – This meteor shower, coming from within the “Little Dipper” will never rise nor set and you can watch it all night; however, best observations would be about 11 p.m. local time and into the early morning hours. However, the light from the full moon this year will blind out all but the brightest meteors. The meteoroids in this group have origins with the famous Comet Tuttle, and leave many spectacular wakes and smoky trails in their wakes. Up to 20 meteors per hour under dark skies can be see to any observer looking nearly due north and “up” a bit!
Mercury will be an “evening star” at the very beginning of the month, but will be too close to the Sun to observe for the rest of the month. This is an unfavorable apparition for observers in the northern hemisphere, but a good one for southerners.
Venus is a brilliant “morning star” all month. It reaches greatest brilliancy on December 4.
Mars is pretty much lost in evening twilight, on the far side of the Sun.
Jupiter is well placed all evening, dominating the southern sky. It is in the constellation Aquarius for the first half of the month, moving into Pisces on December 17. It sets around midnight.
Saturn is now a morning “star” in Virgo. Its rings have returned to their usual glory after being on edge for the last two years.
Uranus is in Pisces all month, and remains within a few degrees of Jupiter.
Neptune is in Capricornus and sets around 10 p.m.
Moon Phases (PST = UT+8)
New Moon: Dec. 5 at 17:36 Universal Time (UT)
First Quarter: Dec. 13 13:59 (UT)
Full Moon: Dec. 21 08:13 17:27 (UT)
Last Quarter: Dec. 28 04:18 (UT)
To remind you of the important astronomical events this month, here is a poster created by UP Astronomical Society member, Carlo Selabao.
Clear skies to all!
Stellarium Planetarium Software