[Prev][Next][Index][Thread]

(meteorobs) NAMN Notes: October 1998

******************************
NAMN Notes: October 1998
******************************

Contents:

1. Giacobinids this October...
2. Memories of Giacobinids...
3. Other October Showers...
4. Upcoming Meetings...
5. For more info...


1. Giacobinids this October...

The maximum of this year's Draconid (DRA) shower is on October 8th, with a
radiant at 262 i.e. RA 17h28m, Dec +54, and meteors may be seen from October
6th to 10th. These meteors are slow, with velocities of about 20 km/sec.
They are referred to as Draconids as they seem to radiate from the head of
the constellation Draco, the dragon.

This shower is also referred to as the Giacobinids, after its parent body,
Comet Giacobini-Zinner, discovered by Giacobini in 1900, and re-discovered
by Zinner in 1913. Giacobini-Zinner is a short period comet, returning
about every 6.61 years. It is interesting to note that the last year we
experienced an outburst of meteors, 1946, the comet itself was experiencing
an outburst in brightness. The meteor shower component has been observed
since 1926. The comet is currently visible in amateur telescopes at:

21P/Giacobini-Zinner
Date(00UT) R.A. (2000) Dec Mag
09-29 17h16.3m +10d35' 10.7
10-04 17h28.1m +08d42' 10.5
10-09 17h41.1m +06d44' 10.3
10-14 17h55.4m +04d40' 10.0
10-19 18h11.0m +02d28' 9.8
10-24 18h27.8m +00d11' 9.6
10-29 18h46.3m -02d13' 9.4
11-03 19h06.1m -04d43' 9.2

In a normal year, meteor rates from this comet are very low or non-existent.
However, this shower has created brief periods of storm activity on a number
of occasions. This year may be one of those outburst years, due to the
relationship in the position of our earth to the dense portion of the
cometary debris field in space. This happened last in 1946, and a meteor
storm was recorded by visual, radar, and photographic means. In 1946
reported visual rates were about 4000 per hour, with radar rates reaching
10,000 per hour.

One interesting feature in 1946 was a 'dip' in activity between 2 parts of
the outburst, indicating a less dense part of the debris field that we were
encountering. About 3/4 of the total outburst occurred within one hour, and
the whole duration was only 3 hours.

As the Giacobinids occur just past full moon this year, shower rates will be
hampered, but could still appear quite extraordinary. Observers on the west
coast of North America seem to be favored, and should observe as soon as
darkness is available on the evening of October 8th. The peak of the shower
is fairly narrow, with storm activity, should it occur, probably lasting no
more than several hours. Nights before and after the maximum should also be
monitored, however, in case of unusual activity. Even negative results (i.e.
little or no activity) are very useful to record in order to help define
this meteor shower better.


2. Memories of Giacobinids...

Memories of the 1946 Giacobinid storm still remain strong in the minds of
those who were fortunate enough to witness the event. One of these people
was Stan Mott, a elderly member of the Royal Astronomical Society of Canada,
who was the recorder on the Giacobinid meteor expedition headed by the late
Dr. Peter Millman. Cathy Hall talked to Stan, now in his 70's, about some
of the details of the expedition, and his impressions of the meteor storm...

Stan traveled with Dr. Millman's group by plane to North Bay, Ontario to
observe, as the weather looked like it was going to be cloudy in Ottawa.
Apparently, it did clear off in Ottawa, but they had decided not to take any
chances. There were 4 observers, and Stan as recorder. The sky conditions
were good, and the temperature a bit cold. They used heavy blankets and
chairs, no sleeping bags, and in Stan's words, looked like 'Tibetan monks
studying the stars for omens'...

All the meteor recording was done by hand - no tape recorders! Stan said
the rates kept him 'very busy'. He said there were just so many... that for
every meteor he recorded for the group members, that he probably saw about 6
himself. However, he said he couldn't really stop to watch the sky a lot -
as he was the recorder. He said it 'really did look like a shower', and
that 'the meteors were coming fast and furious, with several at any
instant'.

There were so many meteors that they just started watching specific areas,
like the head of Draco. "It looked like the eyes were just winking" Stan
said, with all the many point meteors. When asked if there were lots of
both bright and faint meteors, he said that most seemed to be about
magnitude 2... but then added that they gave up on anything fainter than
about magnitude 3! He said there were a mixture of long and short meteors,
and that some had trains. Most of the meteors appeared to be white in color.

How did they manage to record the meteors with so many coming down? Stan
replied 'poorly' and then smiled...

Another friend in Ottawa also observed the 1946 Giacobinids. Mary
Henderson, then a girl of about 16, watched the display from the countryside
just east of Ottawa. She had first noticed the shower from the driveway of
her house in the city, and got her father to drive her out into the country.
This was the first astronomical event she had ever taken note of, so was not
familiar with the normal data that one would want to record.

Having since observed meteors seriously, however, she has been able to give
some comments on the 1946 storm. She said the sky was dark and clear in
Ottawa. The meteors seemed shorter than Perseids, or that was the
impression she remembers. There were a mixture of magnitudes. She doesn't
recall whether there were trains or not, as she didn't know what a train was
at the time. When asked if there was any color to the meteors, or if they
just were mainly white in color, she said that she 'didn't realize that
stars had any color' at the time, so no, did not note any in the meteors.

She watched for several hours, and in her words, 'was just totally
overwhelmed at the marvelous display'. When asked if she noticed any lull
in activity, she said no, she had no impression of any lull. They were just
coming down 'so fast and furious'.

Mary went on after that to become a summer student at the Dominion
Observatory in Ottawa in the summer of 1951, and was given the project in
the summer of 1952 of helping Dr. Millman analyze photographs of the
Giacobinids taken by a news photographer in Chicago...


3. Other October Showers...

The Orionids (ORI) are the major shower of October, and are a reliable
yearly shower, with a ZHR, zenithal hourly rate, of about 20 meteors per
hour with the naked eye. The maximum is on October 21st, with a radiant at
095 i.e. RA 06h20m, Dec +16. Shower members can be seen from about October
2nd to November 7th. The meteors are fast, at about 66 km/sec, and have as
their parent body, Comet Halley.

The Orionids are an excellent shower for new observers. The rates remain
high for at least a couple days, and many of the meteors have trains left
behind them. In recent years, some increased numbers of brighter meteors
have also been seen. The conditions are excellent this year as the shower
is close to new moon. At the maximum, the radiant is near the left foot of
Gemini, in the top left part of the constellation of Orion.

There are a number of minor showers in October as well. Minor showers have
much weaker rates, usually only several meteors per hour, even on their best
night, so extra care must be taken when observing them.

The October Arietids (OAR) reach a maximum on October 8th, near full moon.
The radiant is at RA 02h08m, Dec +08. The meteors are slow, at about 28
km/sec. They can be seen all month, but the rates are very low.

The epsilon Geminids (EGE) reach maximum on October 18th, close to new moon.
The radiant is at 102 i.e. RA 06h48m, Dec +27. These are fast meteors,
at about 70 km/sec. They can be seen in the last half of October, from
about the 14th to the 27th. The rates are also low, only about 2 meteors
per hour, on the maximum night. The parent body is believed to be either
Comet Ikeya 1964VIII, or Comet Nishikawa-Takamizawa-Tago 1987III.

Lastly, the Leo Minorids (LMI) reach a very weak maximum on October 22nd at
RA 10h48m, Dec +37, with fast meteors, about 62 km/sec. Their activity
period, besides being extremely weak, is also very short, from about October
21st to 23rd.


4. Upcoming Meetings...

The Asteroids, Comets, Meteors 1999 Conference is being held July 26-30,
1999 at Cornell University, near Ithaca, in New York State. Details are
available at their website: http://scorpio.tn.cornelldot edu/ACM/. You can
also leave your name and address, to be contacted with more information. A
number of North American amateurs are planning to attend...


5. For more info...

Contact:
Mark Davis, MeteorObs@charlestondot net
Mt. Pleasant, South Carolina, USA
Coordinator, North American Meteor Network

And check out:
NAMN home page:
http://medicine.wustldot edu/~kronkg/namn.html

====================================
Here's to 'Clear Skies' for October!...

October 1998 NAMN Notes co-written
by Mark Davis and Cathy Hall
====================================
Follow-Ups: