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(meteorobs) NAMN Notes: May 2000



*********************
NAMN Notes: May 2000
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Introduction:

NAMN Notes is a monthly newsletter produced by the North American Meteor
Network, and is available both via email, and on the NAMN website at:
http://web.infoavedot net/~meteorobs

Contents:

1. The Eta Aquarids...
2. Other May Showers...
3. Genealogy vs. Meteors...
4. Recent Observations, April 2000...
5. NAMN Member Bags Second Comet...
6. Upcoming Meetings...
7. For more info...


1. The Eta Aquarids...

The Eta Aquarids (ETA) are the first big meteor shower of spring.  They
reach a maximum on May 5th this year, at 17h UT (Universal Time).  The
Zenithal Hourly Rate (the number of meteors one would expect to see under a
dark country sky if the radiant, the position in the sky where the meteors
seem to come from, is directly overhead), would be about 60 meteors per hour
per person - with the unaided eye.  This rate is occasionally variable.
These are fast meteors, with a velocity of about 66 km per second, and can
be seen until about May 28th.

Depending on your latitude, this can be a very good meteor shower.
Observers in more southerly locations are favored, as they will have the
meteor radiant higher in the sky, and so will see the highest rates.
However, it is well worth observing this shower even if you are in a more
northerly location.  This is right at new moon, so sky conditions will be
optimal.  On May 5th, at maximum, the radiant will be at 338 degrees, ie. RA
22h 32m, Dec -01, very near the star eta Aquarius.

Check out the star charts at http://web.infoavedot net/~meteorobs/charts.html,
and print yourself off the set of four (set your printer to landscape mode
before printing).  Aquarius is on chart #3.  These star charts, prepared by
the North American Meteor Network, will help you learn your way around the
sky as well as the brightness of the 'standard' stars that we use to
estimate meteor brightness, called magnitude.</p>

The website of the International Meteor Organization (IMO) has the Eta
Aquarid radiant plotted for the month of May on a star chart at
http://www.imodot net/calendar/cal00.html#eta-Aquarids

According to the IMO:  "This is a fine, rich stream... but it is visible for
only a few hours before dawn essentially from tropical and southern
hemisphere sites.  Some useful results have come even from sites around
40&deg; N latitude in recent years however, and... the shower would benefit
from increased observer activity generally...  A relatively broad maximum,
sometimes with a variable number of submaxima, usually occurs in early May.
ZHRs are generally above 30 for almost a week centered on the main peak...
The fast and often bright meteors make the wait for radiant-rise worthwhile,
and many events leave glowing persistent trains after them."

The Eta Aquarid meteor shower represents debris from Halley's Comet, so this
is a very special shower for many observers due to the popularity of the
parent comet.


2.  Other May Showers...

The Sagittarids (SAG) continue to represent the ecliptic activity - the
meteor activity whose radiant travels along the path of the ecliptic.  These
have a velocity of about 30 km per second, so are verging on slow (note that
slow implies a velocity of under about 30 km per second, medium a velocity
from about 30 - 50 km per second, and fast a velocity of over 50 km per
second).  The ZHR rate for this activity is about 5 meteors per hour.  On
May 5th, the radiant will be at 236 degrees, ie. RA 15h 44m, Dec -20, which
is near the star kappa Libra, about 5 degrees to the right of the top of the
'J' in Scorpius.  By May 30th, the radiant will have moved to 256 degrees,
ie. RA 17h 4m, Dec -23, which is about 8 degrees up to the left of the
reddish star Antares.  Fireballs are possible with this shower, so observers
are often rewarded with sightings of nice, bright meteors.

New moon this month is on May 4th, 1st quarter on May 10th, full moon on May
18th, and last quarter on May 26th.  A moon calendar is provided on the IMO
website at http://www.imodot net/calendar/cal00.html#Table4

For those of you wishing to check out what satellites will be visible while
you're out meteor observing this month, check out
http://www.heavens-above.com


3.  Genealogy vs. Meteors...

After spending some quality family time over this past month's Easter
weekend, the Canadian co-author thought of an interesting analogy - between
genealogy and the study of meteors and comets.

There has been a lot of discussion over the past months on the meteor email
list using technical terms that can be very confusing for a beginning
observer.  There are also many concepts out there in meteor observing that
can be difficult to understand.  And - all this technical talk can make a
beginner wonder if it's all just too much for them, and if their own
observing is of much use at all, given the type of results posted by many of
the more experienced observers.

What are some of these confusing terms and concepts?  Recent ones talked
about on the meteor email list include such things as antihelion, apex and
antiapex activity - and are enough to make a newbie's head spin.  Does a
beginner have to deal with all these terms?  The simple answer is - no.
These are projects for more experienced observers, and beginning observers
are encouraged to just go out under a dark sky and start off with trying for
the major meteor showers - such as the Eta Aquarids this month.

Think of meteor showers as belonging to a big family tree.  Genealogy is a
great hobby, and really does parallel the study of meteors, comets and
asteroids to some degree.  Way back up the family tree, you have
great-grandparents.  Maybe you have a couple large cometary bodies, way out
in space.  These get perturbed, quite possibly by gravitational interaction
with large planets, and end up in orbits around our sun.  Maybe one ends up
in a low inclination orbit (ie. close to what we call the ecliptic plane)
and the other comet body ends up in a high inclination orbit.  Over the
years, these comets loop in toward us again and again in their orbits around
our sun, leaving debris in their path as they shed material.

Maybe one breaks up.  Suppose one of the great-grandparent comets breaks up
into a couple smaller comets - grandparents on the genealogical scale.
These, over time, maybe drift apart a bit, as many siblings often do.  Then,
in their passages over the centuries around our sun, maybe both of them
break up into a couple more pieces, forming parents, one notch further down
the family tree.  So, we now have a number of comets, related in origin,
where we originally had one (we will ignore inbreeding).  Remember that
the second great-grandparent comet never broke up, and is still out there,
orbiting away.

Each time one of these comets goes around our sun, material is shed, which
gradually spreads out along the path of the comet.  Generally speaking,
older comets have been around more times, so their material will be more
spread out along their path.  Younger comets will have their debris more
concentrated and not as spread out along their orbit.  Is there just one
path for debris?  No.  Every time a comet goes around the sun, its path is
just a little bit different from its previous passage.  It has gotten older,
maybe slowed down a bit, and has been affected in various ways by what it
has encountered on its long trip.  So, each time the comet does the loop
around our sun, it lays down a slightly different path of debris.  To
complicate this, each debris path of potential meteors, once formed, acts as
a separate entity.  Each stream of debris is affected by various external
forces that will move and shape it, independent of streams of debris laid
down in different years.

We get meteors when the earth encounters this comet debris.  How on earth do
we tell who this debris belonged to - whether it was from a
great-grandparent (before one of them split up), or from a grandparent, or
from a parent?  This is difficult, and a challenge.  In most cases, this has
been done by photographic studies by professionals, who have analyzed the
characteristics of the meteors and matched those orbital characteristics up
with the corresponding comet.  We now know, for instance, that Comet Halley
spawned both the Eta Aquarid shower that we watch in May, and the Orionid
shower, which we watch in October.

So, what are these unusual terms that some people have been using on the
meteor list lately?  Remember the great-grandparent comets we mentioned
earlier.  One was in a low-inclination orbit, in other words, moving close
to our ecliptic.  Over many centuries, lots of old comets in similar orbits
have shed so much debris that there is very little left of them.  And, more
to the point, because of so much debris along the ecliptic, we are no longer
able to separate the different meteor showers generated by all these old
comets.  They have become 'lost cousins' so to speak.  What are they?  They
are called the 'ecliptical showers' or the 'antihelion activity'.  Don't get
confused though - they are just meteors whose parentage we can't separate.

Similarly, remember the great-grandparent comet in a high inclination orbit.
Over many centuries, these types of old comets also generate meteor debris.
These meteors come from certain specific areas in the sky as well - and are
called the 'toroidal' activity. These are also 'lost kids' whose origins and
parentage have all been mixed in together.

So, what are these terms 'apex' and 'antiapex' that we hear a lot of these
days?  Well, think of driving to the family reunion in a rainstorm.  Your
car is the earth, travelling through space.  If your vehicle is an old
Meteor or Comet, try to suspend your belief here for a moment and pretend
you're driving the earth!  What splats on the front windshield are the apex
meteors.  What you see out the back window are the antiapex meteors.

So, whose parentage can we really separate out and trace on our meteor
family tree?  We can trace many showers to their parent bodies, but not all.
Some of these parents are comets, and some are actually asteroids.  There is
a fine dividing line between comets and asteroids, and this line is still
being studied in scientific circles.  The Perseids are debris from Comet
Swift-Tuttle.  The Geminids are debris from the asteroid Phaethon.  The
Taurid meteor showers in November have an extremely complicated family tree,
with multiple related objects of possible origin.

If you like both genealogy and meteors, get yourself a copy of the IMO
Handbook for Visual Meteor Observers.  It is fascinating reading.  It gives
not only great information on how meteors were formed and what parents they
come from, but also provides an excellent guide to observing them, shower by
shower throughout the year.  Hey, even if you're not into family tree
research, the IMO Handbook is a valuable resource!  Check out the IMO
website at http://www.imodot net under Publications.

(For more information on comets and parent bodies, check out the newly
released 'Comet Science - The Study of Remnants from the Birth of the Solar
System' by Jacques Crovisier and Therese Encrenaz, just released in the
English translation by Cambridge University Press, 2000.  It is a bit
technical, but quite readable by the serious amateur, and is wonderfully
laid out with dozens of photos, easy to read graphs, and charts on all
aspects of comets.  It is available both in hardcover, and the more
affordable softcover.  It's one of the neatest books on comets the
co-author has seen in years.)

When you are actually going out to observe, we encourage beginning meteor
observers to just concentrate on the major showers.  These have good hourly
rates for observers who are learning the sky and where the various
constellations are.  For help on how to get started, check out the NAMN
Observing Guide at http://web.infoavedot net/~meteorobs/guide.html.

For those observers who have gotten through the basics, we then suggest
trying some of the minor meteor showers, and perhaps getting into plotting
meteors on star charts, which is the best way to record detail for minor
showers.  The complete NAMN 2000 Meteor Shower Calendar is at
http://web.infoavedot net/~meteorobs/2000targets.html.

It is probably only the more experienced observers who may want to get into
studying such unusual activity as the 'antihelion' meteors and the other
unusual types of old comet debris. Just remember though - whether a beginner
records data on a major shower, or whether an experienced observer records
data on the 'lost kids' of the meteor family tree - our meteor community
needs all observers, regardless of what activity you would like to help out
with!


4. Recent Observations, April 2000...

Nightly coverage during the month of April remained nearly identical to that
of March with 16 separate nights having at least one NAMN member out
observing. But the total number of hours these observers spent recording
meteors nearly doubled to over 75 hours. In April, 11 members participated
in one or more of these watches.

The highlight of April is normally the Lyrids, but with moon conditions
unfavorable in 2000, only 96 members of this shower were recorded by NAMN
members. Still, that is over three times the number of members from the
other two showers that were visible (ignoring a handful of early Eta
Aquarids that were reported) - Virginids (26 meteors) and the Sagittarids
(26 meteors). And as usual, the sporadics dominated the total number of
meteors category with a total of 444 being recorded.

It was great to pick up some new, active observers during this past month.
Welcome to Michael Shorten of Illinois, Asdai Diaz of Cuba, and Andreja
Cvetko, Natasa Petelin, Maja Plajh and Helena Rojht, all from Slovenia! We
look forward to working together on future NAMN campaigns, and of course, to
receiving your future reports.

For a complete listing of April observations, visit the home page of NAMN at
http://web.infoavedot net/~meteorobs. I would like to thank the following
observers who sent in observations during the month of April:

Jure Atanackov     Scott Moser
Andreja Cvetko     Natasa Petelin
Asdai Diaz         Maja Plajh
Javor Kac          Helena Rojht
Mike Linnolt       Michael Shorten
Robert Lunsford    Kim Youmans


5. NAMN Member Bags Second Comet...

Michael Boschat does it again - a second comet!! According to the Minor
Planet Electronic Circular 2000-J05 issued on May 1, 2000:

-----
COMET C/2000 H2 (SOHO)

Observer details:
249 SOHO. SOHO-LASCO coronagraphs C3 and C2. Comet reported by T. Lovejoy,
M. Boschat, M. Oates and R. Gorelli, measurements by D. A. Biesecker and D.
Hammer, reduction by B. G. Marsden.
-----

Images of C/2000 are available at Mike's website:
http://www.atm.daldot ca/~andromed/

We can only wonder if this will become a regular feature of NAMN Notes. Way
to go Mike!!!


6. Upcoming Meetings...

July 9-12, 2000 - Austria:
The international conference 'Catastrophic Events and Mass Extinctions:
Impacts and Beyond' will be held at the University of Vienna in Austria.
This is the 4th in a series of meetings on mass extinctions and global
catastrophes, the previous meetings being 1981 and 1988 in Utah, and 1994 in
Houston, Texas. Expected topics include impact events in earth history,
boundary events in geologic time, environmental consequences of impacts,
interpretation of stratigraphic records, and extraterrestrial influences
such as asteroids and comets. More information on the conference can be
found at:
http://www.lpi.usradot edu/meetings/impact2000/impact2000.2nd.html

July 25-August 4, 2000 - Slovenia:
An International Astronomical Camp, IAC 2000, will be held in the Pohorje
Mountains at Mariborska koca (MBK), Slovenia. Work will be divided into
various groups - Solar System, Meteors, Deep Sky, Variables and double
stars, and Astrophotography. For more information, contact Jure Zakrajsek
by email at elizabeta.zakrajsek@guest.arnesdot si

September 11-15, 2000 - Crimea:
The international conference 'Space Protection of the Earth - 2000' will be
held in Evpatoriya in the Crimea. This is the 3rd in a series of
international conferences on the protection of the Earth from the threat of
its collision with asteroids and comets, with the prior meetings being held
in Saint Petersburg and Snezhinsk, Russia. Topics will cover characteristics
of asteroids and comets, their risk, detection technologies, man-made means
of influencing dangerous celestial bodies, planetary defense, international
cooperation, prospects for utilizing asteroid and comet resources, and other
issues. For more information, contact the SPE-2000 Program Committee by
email at: spe@asteroids.ru

September 21-24, 2000 - Romania:
The IMC, International Meteor Conference, of the IMO, the International
Meteor Organization, is being held in Pucioasa, Romania, about 100 km
northwest of Bucharest. It is being organized by the Romanian Society for
Meteors and Astronomy (SARM), in cooperation with the mayoralty of Pucioasa.
Pucioasa can be reached by direct trains and buses from Bucharest, and a
shuttle bus from the Bucharest airport to the conference site is planned.
Accommodation will be provided in double rooms, and meals served at the
restaurant of the hotel close to the conference site. The conference fee
will be 170 DEM. A deposit of at least 100 DEM is requested for those
interested in attending, and a registration form is on the IMO website at
http://www.imodot net.


7. For more info..

Contact:
Mark Davis, MeteorObs@charlestondot net
Goose Creek, South Carolina, USA
Coordinator, North American Meteor Network

And check out:
NAMN home page:
http://web.infoavedot net/~meteorobs
Back issues of NAMN Notes can be found on-line at the website.

To subscribe to the meteor email list or
To find out information on our weekly chat sessions:
Contact Lew Gramer at:
owner-meteorobs@jovian.com

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

May 2000 NAMN Notes co-written
by Mark Davis and Cathy Hall
======================================






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