Wade
Earle captured these Ursids from rural eastern Oregon, USA, on the
evening of December 21, 2020, when the first quarter moon illuminated
the landscape.
The
Ursid
meteor shower is the least observed of the major annual
showers. In the northern hemisphere December nights are cold and often
cloudy. Another hindrance is the fact that it peaks just before the
Christmas holiday when many people are busy with holiday festivities.
This shower is completely invisible from the southern hemisphere as the
radiant lies too far north to be seen from south of the equator this
time of year.
The
Ursids are active from December 13-24 with a sharp maximum on December
22nd. The exact time of maximum activity is predicted to
occur between 9-10 universal time which corresponds to 4-5am EST and
1-2am PST. This timing is highly favorable for North America. Activity
is normally low away from maximum with rates less than 1 shower member
per hour. At maximum activity this source normally adds 5-10 medium
velocity meteors to the 15 or so that are normally seen each morning
hour from dark sky sites. The moon will be near its last quarter phase
and will rise near midnight local standard time on December 22nd.
At
maximum, the Ursid radiant lies just west of the fairly bright (2nd
magnitude) orange star known as Kochab (beta Ursae Minoris). To those
not familiar with star names, this star lies in the bowl of the “Little
Dipper”. This area of the sky lies lowest in the northern sky near 20:00
(8pm) local standard time. This is the worst time to view the Ursids as
most of the activity will occur beyond your line of sight, below the
northern horizon. As the night progresses the Ursid radiant will slowly
rise higher into the northern sky and is best placed during the last
dark hour before dawn. To best view this activity, it is suggested that
you face toward the northern half of the sky. It doesn’t have to be
directly at the radiant, but it’s a good idea to have the radiant within
your field of view to help with shower association. Don’t look straight
up as this is the worst place to look for meteors. Lower you view so
that none of the horizon blocks your view. About halfway up in the sky
is suggested for most observers.
Despite
the bitter cold, try to view for at least an hour. Meteor activity is
notoriously variable and if you view for only a short time, it may occur
during a lull in activity. Viewing for at least an hour ensures you will
see several peaks and valleys of activity. An estimate of your limiting
magnitude is important in your report as it provides the sky condition
during your watch. This is easily done by counting the number of
stars visible with certain areas of the sky. Charts for these areas are
available at:
https://www.imo.net/observations/methods/visual
observation/major/observation/#table1.
Areas 1, 7, and 19 on chart #3 would be the easiest to use. Using more
than one area is also encouraged to provide more estimates. The
conversion table is available in Table 2 on the link provided above. At
least two estimates of the limiting magnitude are requested, hopefully
at the beginning and end of your session. If conditions change during
your session, more estimates will provide a more accurate figure for
your data. Helpful tips for visual observing are also available at:
https://www.imo.net/observations/methods/visual-observation/ and
https://www.imo.net/observations/methods/visual
-
observation/major/observation/
.
In order to submit your observations we suggest that you fill out
an
online visual form provided by the
International Meteor Organization. You must register to provide your
data, but there is a free option for those not wishing to subscribe to
the IMO Journal. Note that not every meteor will be an Ursid. There are
several minor showers also active during this period adding a few
meteors to the hourly total. There are also upwards of 10 random meteors
appearing each hour to add to your count. Therefore, shower association
of each meteor must be included.
Feel
free to also share what you saw by sending an email to me at: lunro.imo.usa@gmail.com
If you have never viewed this shower, this will be a good opportunity,
especially for observers in North America.