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

(meteorobs) NAMN Notes: April 2001

***********************
NAMN Notes: April 2001
***********************

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. Highlight of the Month - the Lyrids...
2. Other April Showers...
3. Index of 2000 Articles...
4. Upcoming Meetings...
5. For more info...


1. Highlight of the Month - the Lyrids...

This year, the Lyrid (LYR) meteor shower reaches maximum activity on
April 22nd, near new moon - so conditions are very favorable for a good
display! The actual time of maximum is 04h UT, Universal Time, on April
22nd. Universal Time is the time at Greenwich, England, so don't forget
to adjust this for where you live. For North Americans, this means the
night of April 21st, which is also a weekend night!

As noted in the International Meteor Organization (IMO) Handbook, the
Lyrids are debris from Comet Thatcher, C/1861 G1. This comet was
discovered by A.E. Thatcher of New York on April 5th, 1861, and
independently by Baeker of Nauen, Germany, with the unaided eye. It
later brightened to about magnitude 2.5, with a tail of about 1 degree
in length. It was determined that the orbit of the comet was
elliptical, and that the comet returns about every 415 years.

The Lyrid shower is the oldest meteor shower for which observations have
been found. It was seen in ancient China over 2000 years ago.
According to the IMO Handbook, the Lyrid meteoroid stream - the actual
debris shed by the comet - is highly inclined in its orbit, meaning that
its path doesn't come anywhere near our solar system's planets, and
hence isn't disrupted by the planets' gravity. Because of this,
although the stream is very old, it acts younger than its age! For instance,
it has a short period of maximum activity, only hours long, and has higher
density concentrations of material - clumps of debris - which can cause
interesting outbursts of activity.

This shower lasts from about April 16th until April 25th. At the time
of maximum activity, the Zenithal Hourly Rate (ZHR), should be about 15
meteors per hour. This means that if you are out under a dark country
sky, with the radiant, the area in the sky where the meteors seem to
come from, directly overhead, then you should see - on the average -
about 15 meteors every hour with your unaided eye.

However, rates for this shower can be variable - up to 90 meteors per
hour! You won't know if you are in for a surprise this year unless you
get outside and take a look!

On the 22nd, the radiant will be at 271 degrees, ie RA 18h 4.2m, Dec
+34, which is approximately halfway between the bright star Vega in Lyra
and the star mu Herculis. To see where this is on a star map, go to our
NAMN Map #3 under http://web.infoavedot net/~meteorobs/charts.html. The
NAMN charts will also give you a refresher course in the spring
constellations - and some 'standard' stars to judge meteor brightness
with.

Meteor radiants do move across the sky from night to night though! The
motion is not very noticeable over a night or two, but over the course
of a week, a radiant is at quite a different place in the sky. For
those of you watching the Lyrids away from the maximum date of April
22nd, look at the Lyrid radiant map on the IMO website, under the 2001
Meteor Shower Calendar: http://www.imodot net/calendar/cal01.html#Lyrids.

These are average velocity meteors, at about 49 km/sec, so will be
easier to observe for beginning observers. These meteors will also be
easier to capture with your camera, as they won't fly by your camera
field quite so quickly. If you want to try some photos, use fast film,
a normal (not a telephoto) camera lens set at almost wide open, and a
cable release and tripod. A series of 10 to 15 minute photos might be
appropriate if your light pollution is not too bad. Meteor photography
is a science itself, but even for beginning observers, it is fun to
try. If you want to read more about how the experts do it, check out
the IMO website at http://www.imodot net/photo/index.html.

If you are new to meteor observing, and just want to go out and see a
meteor shower - then get out a lawnchair and a sleeping bag, and just
enjoy yourself! However, if you would like to try actually recording
meteor data, that we can use for the study of meteors, then check out
our NAMN Observing Guide at :
http://web.infoavedot net/~meteorobs/guide.html.

If you have any questions, drop our NAMN Coordinator an email at
MeteorObs@charlestondot net. We'd love to hear from you - tell us about
your observing experiences!


2. Other April Showers...

The Virginids (VIR), the ecliptical activity, continue into April, as
the radiant moves along the path of the ecliptic in the sky, a little
motion each day. These are almost slow meteors at about 30 km/sec.
ZHR rates will be about 5 meteors per hour. By mid-April, on the 15th,
the radiant will be at 205 degrees, ie RA 13h 40.2m, Dec -8, which is
about 5 degrees up to the left of the bright star Spica, in Virgo.

The pi Puppids (PPU) reach a maximum on April 23rd, right after the
Lyrid maximum, and can be seen from about the 15th to 28th. At maximum
on the 23rd, the radiant will be at 110 degrees, ie RA 7h 19.8m, Dec
-45, which is about 15 degrees due south of the star eta Canis Majoris,
the bottom left foot star of Canis Major. These are nice slow meteors,
with a velocity of about 18 km/sec. ZHR rates are variable, and have
reached as high as 40 meteors per hour on occasion. The pi Puppids are
debris from Comet 26P/Grigg-Skjellerup, discovered in 1902 by John Grigg
of Thames, New Zealand, and J.F. Skjellerup of Cape of Good Hope, South
Africa.

The eta Aquarids (ETA) start to become active about April 19th, although
won't reach a maximum until May 5th. These are fast meteors, at about
66 km/sec. Rates at maximum in early May should reach about 60 meteors
per hour. Rates in April will be much less. On April 20th, the radiant
will be at 323 degrees, ie RA 21h 31.8m, Dec -7, which is about 1 degree
south of the star beta Aquarius, the star called Sadalsuud. Eta
Aquarids are debris from Halley's Comet.

Lastly, the Sagittarids (SAG) start to appear about April 15th, and will
last till about mid-July. This is actually a complex of radiants near
the ecliptic, and is surmised to be the debris from a number of unknown
bodies. On April 20th, the radiant will be at 227 degrees, ie RA 15h
7.8m, Dec -18, which is about 7 degrees due north of the star sigma
Libra, the variable star known as Brachium. These meteors are verging
on slow, with a velocity of about 30 km/sec. ZHR rates are about 5
meteors per hour. Fireballs have been associated with this meteor
shower complex.

Some useful star charts can be printed off from our NAMN website. These
show the constellations, the RA and Dec star coordinates, and the
brightness of certain standard stars to help you judge the
magnitudes of the meteors you see. This set of 4 charts is available
at: http://web.infoavedot net/~meteorobs/charts.html.

There are several bright planets in the sky in April. Mars moves from
Ophiuchus to Sagittarius in the latter part of the month. On April 1st
it is at magnitude -0.2, on April 11th at magnitude -0.5, and by the
21st has brightened to -0.7. Note that the smaller the number, the
brighter the object! Jupiter and Saturn are getting lower in the
western sky, in Taurus. Jupiter is at magnitude -2.1 for most of the
month, and Saturn is at -0.2.

For more advanced reading, or to find out information on other types of
meteor observing - video, photographic, radio, etc. - check out the
website of the IMO at http://www.imodot net. Additional reading on more minor
showers can be found on Gary Kronk's 'Comets and Meteor Showers' website at
http://comets.amsmeteors.org.


3. Index of 2000 Articles...

The following is an index of the various articles that have appeared in
NAMN Notes over this past year. Every issue also contains 'Upcoming
Meetings' and 'For more info' sections.

The articles in NAMN Notes can be accessed and read on the NAMN home
page for about 6 months at: http://web.infoavedot net/~meteorobs

Issues previous to that can be accessed in the meteorobs archive at:
http://www.tiacdot net/users/lewkaren/meteorobs by selecting "Browse
Archive by Month." There are many articles that are very useful to beginners
throughout the year, regardless of what month you are observing!

NAMN Notes: January 2000
Welcome to 2000...
Quadrantids...
Other January Showers...
Closing the Year Out...
Index of 1999 Articles...

NAMN Notes: February 2000
Meteor Newsletters...
February Showers...
Reading for a Winter's Night...
1999 Leonid Results...
Recent Observations, January 2000...

NAMN Notes: March 2000
March Showers...
Constellation Review - Ursa Major...
Xi Bootids Resolved into Two Radiants with German Videos - by G.W. Gliba...
Recent Observations, February 2000...

NAMN Notes: April 2000
Spring Brings the Lyrids...
Other April Showers...
NAMN Member Discovers Comet!...
Constellation Review - Leo...
Recent Observations, March 2000...

NAMN Notes: May 2000
The Eta Aquarids...
Other May Showers...
Genealogy vs. Meteors...
Recent Observations, April 2000...
NAMN Member Bags Second Comet...

NAMN Notes: June 2000
June Showers...
Help for New Observers...
Limiting Magnitude Calculator...
NAMN Member Finds 4 Comets in May!...

NAMN Notes: July 2000
July's Main Shower - the Southern Delta Aquarids...
Other July Showers...
Check out the Heavens Above...
A Comet for July Observers...
NAMN Member Continues Comet Discoveries...

NAMN Notes: August 2000
Main Summer Shower - the Perseids!...
Other August Showers...
Comet Update for August...

NAMN Notes: September 2000
September's Alpha Aurigids...
Other September Showers...
Annual Conference of the IMO...

NAMN Notes: October 2000
Orionids - Debris from Comet Halley...
Draconids and Other October Showers...
Help a Kid to Learn about Meteors...

NAMN Notes: November 2000
Highlight of November - Leonids!...
Other November Showers...
Review of Meteor Trak Software...
Join the IMO...
Update on NAMN Member's Comets...

NAMN Notes: December 2000
December's Geminids...
Other December Showers...
Recent Observations...
Christmas Gift Ideas for Meteor Observers...


4. Upcoming Meetings...

August 6-10, 2001 - Sweden:
The Meteoroids 2001 conference will be held at the Swedish Institute of
Space Physics in Kiruna, Sweden. Topics covered will include historical
observations and perspectives on meteoroids; dynamics, sources and
spatial distribution; detection and characteristics of meteoroids from
interstellar space; the meteoroid interaction process in the atmosphere;
hypervelocity impact effects on spacecraft; Leonid meteor storms;
optical observations of meteors; and meteor radar work. For
information, contact Asta Pellinen-Wannberg at
asta.pellinen-wannberg@irf.se and check out the website at
http://www.irf.se/Meteoroids2001.

September 20-23, 2001 - Slovenia:
IMC 2001, the worldwide meeting for meteor observers of the
International Meteor Organization, will be held this year in the town of
Cerkno, in Slovenia. This is a convention for both amateurs and
professionals. For North Americans not familiar with the map, Slovenia
is on the Adriatic Sea, east of Venice and south of Austria. It is
within driving distance of major European cities. This is a great
opportunity to meet and chat with observers from all over the globe -
and a wonderful excuse to visit Europe as well! Come join us! The
early registration deadline, for reduced registration rates, is July
1st. Details can be found on the IMO website at http://www.imodot net.


5. 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 NAMN website, and
in the meteorobs archives at:
http://www.tiacdot net/users/lewkaren/meteorobs
by selecting 'Browse Archive by Month'

To subscribe to the meteor email list or
To find out information on our weekly chat sessions:
Contact Lew Gramer at:
dedalus@alum.mitdot edu

============================================
Here's to 'Clear Skies' for April...
April 2001 NAMN Notes co-written
by Mark Davis and Cathy Hall
============================================








To UNSUBSCRIBE from the 'meteorobs' email list, use the Web form at:
http://www.tiacdot net/users/lewkaren/meteorobs/subscribe.html