|02||Pheonicid Meteor Shower (ZHR = var)||08:00 PM|
|06||December φ-Cassiopeid Meteor Shower (ZHR = var)||09:00 PM|
|07||Puppid-Velid Meteor Shower (ZHR = 10)||03:00 AM|
|07||Moon passing 1°52' S of Venus||08:49 AM|
|08||Venus at greatest brightness||12:09 AM|
|08||Moon passing 4°11' S of Saturn||09:49 AM|
|09||Monocerotid Meteor Shower (ZHR = 2)||01:00 AM|
|09||Moon passing 4°28' S of Jupiter||02:10 PM|
|12||σ-Hydrid Meteor Shower (ZHR = 3)||03:00 AM|
|14||Geminid Meteor Shower (ZHR = 120)||02:00 AM|
|16||Comae Berenicid Meteor Shower (ZHR = 3)||before dawn|
|19||December Leonis Minorid Meteor Shower (ZHR = 5)||05:00 AM|
|21||December Solstice||11:59 PM|
|22||Ursid Meteor Shower (ZHR = 10)||before dawn|
|Dec 04||03:43 PM|
|Dec 11||09:36 AM|
|Dec 19||12:35 PM|
|Dec 27||10:24 AM|
|Dec 01||06:11 AM||05:27 PM||09:11 AM||08:21 PM||04:49 AM||04:15 PM||11:20 AM||10:53 PM||10:20 AM||09:42 PM|
|Dec 11||06:43 AM||05:53 PM||08:49 AM||08:02 PM||04:40 AM||04:01 PM||10:46 AM||10:20 PM||09:44 AM||09:07 PM|
|Dec 21||07:13 AM||06:23 PM||08:11 AM||07:29 PM||04:31 AM||03:50 PM||10:12 AM||09:48 PM||09:08 AM||08:32 PM|
|Dec 31||07:37 AM||06:53 PM||07:16 AM||06:38 PM||04:23 AM||03:39 PM||09:39 AM||09:16 PM||08:32 AM||07:57 PM|
* = following day
For the whole month of December, the summer constellations can still be observed in the western sky for the first few hours after sunset. The Summer Triangle asterism is still located fairly high in the sky during the first half of the month, with Vega of the constellation Lyra heading west-northwest, Deneb of the constellation Cygnus closest to the zenith, and Altair of the constellation Aquila is heading west southwest (Figures 1a and 1b). The Summer Triangle continues to dive westward and can be observed lying low near the western horizon in late December as seen from Figure 1c .
Figure 1: The view of the night sky at 06:00 P.M. on several days of December 2021 using the Stellarium Application.
Figure 1a. December 1, 2021
Figure 1b. December 15, 2021
Figure 1c. December 30, 2021
The members of the autumn constellations can be notably observed as it gets high in the eastern sky. The view of the observable constellations after sunset in mid-December is shown in Figure 2.
Figure 2. The view of the sky after sunset on mid-December 2021 using the Stellarium application
Cassiopeia, a “W” shaped constellation is going to be very prominent and can be easily seen in the sky due to its unique formation and high position in the north-northwestern sky. When the Big Dipper asterism is not visible in the night sky, Cassiopeia may be used as an alternative to and the position of the north star, Polaris. However, when compared to using the Big Dipper, the result achieved using this method may not be as accurate. The star positioned in the middle of the constellation Cassiopeia can be utilized as a pointer star to lead to the approximate position of Polaris, as shown in Figure 3 .
Figure 3. The view of the northern sky on mid-December 2021 at 09:00 P.M. showing how to locate the position of the north star Polaris using the constellation Cassiopeia using the Stellarium application
For the whole month of December, Venus can be observed in the southwestern part of the sky after sunset, however, in late December, Venus may be already difficult to observe as it is just a few degrees above the horizon. Jupiter and Saturn can also be observed in the southwestern portion of the sky after sunset.
Figure 4. The view of the southwestern sky after sunset on 07 December 2021 showing the Moon-Venus Conjunction using the Stellarium application
The thin crescent Moon will pass 1°52' S of Venus on 07 December 2021 at 08:49 A.M. The exact moment of the Moon-Venus Conjunction cannot be observed since it will occur during the day. However, the close pairing will be visible after sunset at around 05:41 P.M. (Figure 4) at an altitude of 30°above the southwestern horizon. The close pairing may be observed until 08:13 P.M. as the pair sinks towards the horizon. By then, the Moon and Venus will be at mag -10.4 and mag -4.7 and are located both in the constellation Sagittarius .
On 08 December 2021 at 12:09 A.M., Venus will reach its greatest brightness at mag -4.7 .
On 08 December 2021, at 09:49 A.M., the 4-day old Moon will pass 4°11' S of Saturn Again, the exact instance of the crescent Moon-Saturn Conjunction will not be observed as it will occur during the day. However, the view of the conjunction may still be enjoyed after sunset around 05:42 P.M. as the Moon and Saturn will be observed 44° above the southwestern horizon (Figure 5) until the pair sets at around 09:17 P.M. . The Moon and Saturn will be at mag -11.0 and mag 0.5, respectively, and will be both located in the constellation Capricornus .
Figure 5. The view of the southwestern sky after sunset on 08 December 2021 showing the Moon-Saturn Conjunction using the Stellarium application
On 09 December 2021, the Moon will be passing 4°28' S of Jupiter at around 02:10 P.M. The close pairing will be visible after sunset at around 05:42 P.M. at about 57° above the southwestern horizon (Figure 6). The Moon and Jupiter will be at mag -11.5 and mag -2.3, respectively, and will be both located in the constellation Capricornus .
These Moon-planetary conjunctions can be seen through the naked eye or using a pair of binoculars. Please do note that the separation of the above-mentioned conjunctions is too wide to fit in the field of view of a telescope.
Figure 6. The view of the southwestern sky after sunset on 09 December 2021 showing the Moon-Jupiter Conjunction using the Stellarium application
Several meteor showers can be observed for December. The summary details of the observable meteor showers are presented in Table 1. The first column of the table is the name of the meteor shower, which is usually derived from the constellation where the shower's radiant is located. The radiant of the shower, listed in the second column, is a point in the sky where meteors seem to originate. The position of the meteor shower radiants (enclosed in the green solid circle) of the observable meteor showers for December 2021 during its highest position is presented as follows: Pheonicids (Figure 7), December φ Cassiopeids (Figure 8), Puppid-Velids (Figure 9), Monocerotids (Figure 10), σ-Hydrids (Figure 11), Geminids (Figure 12), Comae Berenicids (Figure 13), December Leonis Minorids (Figure 14), and Ursids (Figure 15).
|Meteor Shower Name||Radiant||Active Date||Peak Date||Best Viewed Time||ZHR||Lunar Phase|
|Pheonicids||Phoenix||28 Nov - 09 Dec||02 Dec||08:00 P.M.||var||Waxing Crescent|
|December φ Cassiopeids||Andromeda||01 - 08 Dec||06 Dec||09:00 P.M.||var||Waxing Crescent|
|Puppid-Velids||Vela||01 - 15 Dec||07 Dec||03:00 A.M.||10||Waxing Crescent|
|Monocerotids||Monoceros||05 - 20 Dec||09 Dec||01:00 A.M.||2||Waxing Crescent|
|σ-Hydrids||Hydra||03 - 15 Dec||12 Dec||03:00 A.M.||3||Waxing Gibbous|
|Geminids||Gemini||04 - 17 Dec||14 Dec||02:00 A.M.||120||Waxing Gibbous|
|Comae Berenicids||Leo||12 - 23 Dec||16 Dec||before dawn||3||Waxing Gibbous|
|December Leonis Minorids||Leo Minor||05 Dec - 04 Feb||19 Dec||05:00 A.M.||5||Full Moon|
|Ursids||Ursa Minor||17 - 26 Dec||22 Dec||before dawn||10||Waning Gibbous|
The third column shows the period when the meteor shower is active and can be observed while the Peak Date as shown in the fourth column indicates the point in time when the greatest number of meteors can be observed. The Best viewed time, listed in the fifth column, represents the time when the radiant point is at its highest point in the sky. The Zenithal Hourly Rate (ZHR), listed in the sixth column, indicates the number of meteors an observer can see in an hour during the peak activity. However, the computation of ZHR assumes that one is observing in a perfectly dark and clear sky and the radiant is located directly overhead. The number of ZHR decreases under certain circumstances. The last column shows the phase of the Moon during the peak date of the shower. Unfortunately, the waxing gibbous phase of the Moon during the peak of Geminids and Comae Berenicids, the Full Moon phase during the peak of December Leonis Minorids, and the waning gibbous phase of the Moon during Ursids will produce a significant interference in the meteor shower observation throughout the night.
Meteor showers are can be observed through the naked eyed and there is no need to use special equipment such as telescopes or binoculars. To maximize the viewing experience, it is ideal to observe in a dark site away from the city lights under clear and moonless sky conditions.
*(Click image to enlarge view)
On 04 December 2021 from 01:29 P.M. to 05:36 P.M., the Moon will be passing in front of the Sun, thus, creating a rare astronomical phenomenon called Total Solar Eclipse. Unfortunately, the Total Solar Eclipse will only be visible in Antarctica and not in the Philippines .
On the 12th of December 2021, another comet named C/2021 A1 (Leonard) will make its closest approach to the Earth at a distance of 0.23 AU. The comet, however, will not be visible during its perigee since it will be below the horizon after sunset. Luckily, there are other chances to see the comet on a different day of the month. The position of Comet C/2021 A1 (Leonard) every other night for the whole month of December 2021 is shown in Table 2 .
|Date||Constellation||Observable Time||Highest Position in the Sky|
|01 Dec||Canes Venatici||03:42 A.M. - 05:09 A.M.||37° above NE horizon (at 05:09 A.M.)|
|03 Dec||Bootes||03:57 A.M. - 05:10 A.M.||34° above NE horizon (at 05:10 A.M.)|
|05 Dec||Bootes||04:15 A.M. - 05:11 A.M.||29° above NE horizon (at 05:11 A.M.)|
|07 Dec||Bootes||04:50 A.M. - 05:13 A.M.||23° above NE horizon (at 05:13 A.M.)|
|09 Dec||Serpens Caput||Not observable|
|11 Dec||Ophiuchus||Not observable|
|13 Dec||Serpens Cauda||Not observable|
|15 Dec||Sagittarius||Not observable|
|17 Dec||Sagittarius||Not observable|
|19 Dec||Sagittarius||Not observable|
|21 Dec||Microscopium||06:28 P.M. - 06:33 P.M.||18° above SW horizon (at 06:28 P.M.)|
|23 Dec||Microscopium||06:30 P.M. - 06:42 P.M.||19° above SW horizon (at 06:30 P.M.)|
|25 Dec||Microscopium||06:28 P.M. - 06:42 P.M.||20° above SW horizon (at 06:28 P.M.)|
|27 Dec||Microscopium||06:30 P.M. - 06:43 P.M.||20° above SW horizon (at 06:30 P.M.)|
|29 Dec||Piscis Austrinus||06:31 P.M. - 06:39 P.M.||18° above SW horizon (at 06:31 P.M.)|
|31 Dec||Piscis Austrinus||06:33 P.M. - 06:36 P.M.||18° above SW horizon (at 06:33 P.M.)|
The December Solstice will be on 21 December 2021 at 11:59 P.M. By then, the Sun will reach its most southerly point in the sky, in the constellation Capricornus, at a declination of 23.5°S. During the December Solstice, the northern hemisphere will experience the shortest day and this day also marks the first day of winter. Consequently, in the southern hemisphere, this day marks the first day of summer .
*All times displayed are in Philippine Standard Time (PhST)
 D. Ford, \In-The-Sky.org Guide to the night sky: Conjunction of the Moon and Venus." https://in-the-sky.org/news.php?id=20211207_20_100, Last accessed on 2021-11-4, 2021.
 D. Ford, \In-The-Sky.org Guide to the night sky: Venus at greatest brightness." https://in-the-sky.org/news.php?id=20211207_11_100, Last accessed on 2021-11-4, 2021.
 D. Ford, \In-The-Sky.org Guide to the night sky: Conjunction of the Moon and Saturn." https://in-the-sky.org/news.php?id=20211209_20_100, Last accessed on 2021-11-4, 2021.
 D. Ford, \In-The-Sky.org Guide to the night sky: Conjunction of the Moon and Jupiter." https://in-the-sky.org/news.php?id=20211208_20_100, Last accessed on 2021-11-4, 2021.
 D. Ford, \In-The-Sky.org Guide to the night sky: Total Solar Eclipse." https://in-the-sky.org/news.php?id=20211204_09_100, Last accessed on 2021-11-10, 2021.
 D. Ford, \In-The-Sky.org Guide to the night sky: C/2021 A1 (leonard) at perigee." https://in-the-sky.org/news.php?id=20211212_19_100, Last accessed on 2021-11-10, 2021.
 D. Ford, \In-The-Sky.org Guide to the night sky: December Solstice." https://in-the-sky.org/news.php?id=20211221_07_100, Last accessed on 2021-11-10, 2021.
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