No matter where you live, the first half of
December provides some of the best meteor activity of the year. In the northern
hemisphere the sporadic rates are still strong plus you can also count on strong
activity from the Geminids, which peak on December 13. There are also several
minor radiants that add a few meteors each hour. All of these centers of activity
are located high in the sky during the early morning hours this time of year.
Unfortunately this year the bright moon spoils the show during the first week of
the month. During the second week of December the moon will pass its last quarter
phase and will not be such a nuisance .
As seen from the southern hemisphere the sporadic
rates are increasing toward a January maximum. Shower rates are also good but the
Geminids suffer a bit from the lower elevation seen from southern locations. Still
with the warmer weather now occurring south of the equator, December is a great
time to view celestial fireworks.
During this period the moon reaches its last quarter
phase on Wednesday December 9th. On that date the moon lies ninety degrees west of
the sun and rises near midnight local standard time (LST). This weekend the waning
gibbous moon will rise during the evening hours and remain in the sky the remainder
of the night. The bright glare from the gibbous moon will make it difficult to view
any meteor activity. Once the moon passes its last quarter phase the moonlight becomes
less of a problem. The estimated total hourly rates for evening observers
this week is near three as seen from the northern hemisphere and two from the
southern hemisphere. For morning observers the estimated total hourly rates should
be near ten from the northern hemisphere and seven as seen from the southern
hemisphere. The actual rates will also depend on factors such as personal light and
motion perception, local weather conditions, alertness and experience in watching
meteor activity. Morning rates are reduced during this period due to moonlight.
The radiant positions and rates listed below are exact
for Saturday night/Sunday morning December 5/6. These positions do not change
greatly day to day so the listed coordinates may be used during this entire period.
Most star atlases (available at science stores and planetariums) will provide
maps with grid lines of the celestial coordinates so that you may find out exactly
where these positions are located in the sky. A planisphere or computer planetarium
program is also useful in showing the sky at any time of night on any date of the
year. Activity from each radiant is best seen when it is positioned highest in the
sky, either due north or south along the meridian, depending on your latitude. It
must be remembered that meteor activity is rarely seen at the radiant position.
Rather they shoot outwards from the radiant so it is best to center your field of
view so that the radiant lies at the edge and not the center. Viewing there will
allow you to easily trace the path of each meteor back to the radiant (if it is
a shower member) or in another direction if it is a sporadic. Meteor activity is
not seen from radiants that are located below the horizon. The positions below
are listed in a west to east manner in order of right ascension (celestial longitude).
The positions listed first are located further west therefore are accessible earlier
in the night while those listed further down the list rise later in the night.
The full descriptions of each active meteor shower will continue next week when
the moon becomes less of a nuisance to observers.
The table below presents a condensed version of the expected activity this week.
Rates and positions are exact for Saturday night/Sunday morning but may be used
all week long.
| SHOWER | DATE OF MAXIMUM ACTIVITY | CELESTIAL POSITION | ENTRY VELOCITY | CULMINATION | HOURLY RATE | CLASS* | RA (RA in Deg.) DEC | Km/Sec | Local Standard Time | North-South | Phoenicids (PHO) | Dec 06 | 01:12 (018) -53 | 18 | 20:00 | <1 - <1 | III | Northern Taurids (NTA) | Nov 13 | 05:16 (079) +26 | 29 | 00:00 | 2 – 1 | II | Monocerotids (MON) | Dec 08 | 06:32 (098) +08 | 41 | 01:00 | <1 - <1 | II | Geminids (GEM) | Dec 13 | 07:10 (107) +33 | 35 | 02:00 | 2 – <1 | I | Puppid-Velids (PUP) | Dec 07 | 08:10 (122) -45 | 40 | 03:00 | <1 - 2 | II | Sigma Hydrids (HYD) | Dec 06 | 08:16 (124) +03 | 61 | 03:00 | <1 - <1 | II | December Leonis Minorids (DLE) | Dec 20 | 09:58 (149) +37 | 64 | 05:00 | <1 - <1 | II | Psi Ursa Majorids (PSU) | Dec 05 | 11:19 (170) +43 | 61 | 06:00 | <1 - <1 | IV | Alpha Draconids (DAD) | Dec 05 | 13:34 (204) +60 | 44 | 08:00 | <1 - <1 | IV |
You saw something bright and fast? Like a huge shooting star? Report it: it may be a fireball. 
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