[BAA-ebulletin 01022] GOOD PROSPECTS FOR THIS YEAR'S GEMINID METEOR SHOWER

[BAA electronic bulletins service]

GOOD PROSPECTS FOR THIS YEAR'S GEMINID METEOR SHOWER

 

Active from December 6-17, but with a slow rise to maximum, the Geminids are
currently the richest of the regular annual meteor showers, producing an
abundance of bright meteors, with rates outstripping those of the August
Perseids for a 24-hour interval centred on their 14 December maximum - a
real treat for observers prepared to brave the winter winds, cold and damp. 

            The other good news is that Geminid maximum this year coincides
with a First Quarter Moon in Aquarius, so there will be little interference
by moonlight, enabling many fainter meteors to be seen in addition to the
brightest members of the shower.  This year, the time of Geminid maximum is
favourable for observers on the East Coast of the USA, with peak activity
expected at about 08h on Friday, December 14, when the ZHR may again reach
100 to 120 meteors per hour. 

       The Geminid shower radiant (at RA 07h 33m,  Dec +32o, just north of
the first magnitude star Castor) rises early in the evening and reaches a
respectable elevation above the horizon (> 40o) well before midnight, so
observers who are unable to stay up late can still contribute very useful
watches. However, the early morning hours of Friday, 14th December are
likely to yield the greatest Geminid activity for observers in the UK, when
the radiant is high in the sky and rates are climbing towards the peak
around dawn.

            In recent years from the UK, the Geminids have shown typical
peak observed rates of 70-80 meteors per hour in good skies. The maximum is
quite broad, however, and respectable Geminid rates may be expected
throughout the nights of December 13/14 and 14/15.  Past observations have
shown that bright Geminids become more numerous some hours after the rates
have peaked, a consequence of particle-sorting in the meteoroid stream.

      As with any meteor shower, when observing the Geminids it is best to
look at an altitude of 50o (about the same altitude as the Pole Star from
southern parts of the UK) and 40-50o to either side of shower radiant,
rather than looking directly at the radiant itself, although Geminid meteors
may appear in any part of the sky. December nights can be quite chilly,
especially in the early morning hours, so wrap up well with plenty of layers
of warm, dry clothing and make sure that you wear a hat, gloves, thick socks
and sensible waterproof footwear. 

      Geminid meteors enter the atmosphere at a relatively slow 35
kilometres per second, and thanks to their robust (presumably more rocky
than dusty) nature tend to last longer than most in luminous flight. Unlike
swift Perseid or Orionid meteors, which last only a couple of tenths of a
second, Geminids may be visible for a second or longer, sometimes appearing
to fragment into a train of 'blobs'. Their low speed and abundance of bright
events makes the Geminids a prime target for imaging.

      The Geminid shower has grown in intensity over the past 50 years as a
result of the stream orbit being dragged gradually outwards across that of
the Earth. A consequence is that we currently encounter the most
densely-populated parts of the stream. This happy situation is unfortunately
only temporary - in a few more decades, Geminid displays can be expected to
diminish in intensity. Here we have an excellent opportunity to follow, year
on year, the evolution of a meteoroid stream. 

      The BAA's visual meteor report forms, available as downloads in both
pdf and Excel formats, enable observers to record the details of each meteor
seen. These include: time of appearance (UT); apparent magnitude
(brightness); type (shower member, or random, 'background' sporadic);
constellation in which seen; presence and duration of any persistent train.
Other notes may mention flaring or fragmentation in flight, or marked
colour. Watches should ideally be of an hour's duration or longer (in
multiples of 30 minutes). Observers are reminded to carefully record the
observing conditions and the stellar limiting magnitude. Wrap up warmly and
enjoy what should be a great show!

      By whatever means you observe the Geminids this year, please submit
your results to the BAA Meteor Section via meteor at britastro.org.

      

 

Dr John Mason

Director, BAA Meteor Section

email: docjohn at dircon.co.uk

 

2018 December 10