(meteorobs) NAMN Notes: April 2007

[Mark Davis]

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NAMN Notes:  April 2007
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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://www.namnmeteors.org


Contents:

1.  Lyrids - Our Spring Shower...
2.  Other April Meteor Activity...
3   International Astronomy Day...
4.  Upcoming Meetings...
5.  For more info...


1.  Lyrids - Our Spring Shower...

The Lyrids (LYR) are the meteor highlight for the month of April, and herald
our spring season.

The Lyrid shower is the oldest meteor shower for which observations have
been found.  It was seen in ancient China over 2,000 years ago.  According
to the IMO Handbook, of the International Meteor Organization, the Lyrid
meteoroid stream - the actual debris shed by its parent comet - is highly
inclined in its orbit.  This means that its path doesn't come near our solar
system's planets, and hence is not disrupted by those planets' gravity.
Because of this, although the stream is very old, it acts younger than its
age.  It has a short period of maximum activity, usually only hours long,
and has higher density concentrations of material - clumps of debris - which
can cause interesting outbursts of activity.

Do all meteor showers have comets as parents?  No, but the Lyrids do.  They
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 brightened to about magnitude 2.5
with a tail of about 1 degree in length.  That means it was slightly fainter
than the stars in the Big Dipper with a tail about 1/5 the distance between
the pointer stars of the Dipper.  It was determined that the orbit of the
comet was elliptical, and that the comet returns to our area of the solar
system about every 415 years.

This year, the Lyrid meteors are predicted to reach their highest rates on
April 22nd at about 22h30m UT, Universal Time in Greenwich, England.  For
east coast North American observers, this means about 6.30 pm EDT.
However - the peak time can vary, and could occur anytime between 14h45m UT
on the 22nd and 1h45m UT on the 23rd.  For EDT, subtract 4 hours.  Lyrids
can be seen from about April 16th to the 25th.

They are average velocity meteors at about 49 km per second.  ZHR rates on
the 22nd are predicted to peak at about 18 meteors per hour.  What is ZHR?
ZHR refers to Zenithal Hourly Rate, and is the number of meteors that an
observer would expect to see in an hour, if they are out under a dark
country sky, and if the radiant, the area in the sky where the meteors seem
to come from, is directly overhead.  Occasional outbursts of activity have
occurred in the past - up to 90 meteors per hour.  Enhanced rates around the
peak time, where rates are at least half the peak rates, can last from about
15 hours (as in 1993) to 62 hours (as in 2000).

Where is the radiant for the Lyrids?  It's in the constellation of Lyra the
Lyre.  In ancient mythology, the lyre was the musical instrument of Orpheus.
Orpheus was a son of Apollo, a god of prophecy.  His mother was Calliope,
the muse of epic poetry.  Orpheus was a gifted minstrel - it was he who
saved Jason and the Argonauts in their quest for the Golden Fleece by
drowning out the sounds of the Sirens with his playing.  Orpheus married
Eurydice, a nymph, who was unfortunately bitten by a snake and died.
Orpheus was extremely upset and took a trip to the underworld to somehow
get her back by charming everyone with his playing.  The rulers of the
underworld, Hades and Persephone, agreed on the condition that once back on
earth, Eurydice always follow behind Orpheus and he not turn around to look
at her.  When he failed in this and turned to look at his wife, Eurydice
was zapped back to the underworld, and poor Orpheus was left all alone.

Orpheus wandered around for many months playing his musical lyre.  He
met his end when he refused the advances of a band of drunken female
followers of Dionysus and the women tore him limb from limb taking his
head to the island of Lesbos.  His body - the rest of it - was buried in
Thrace, where supposedly nightingales now sing sweetly.  The god Apollo
gathered up the musical lyre of Orpheus and placed it in the heavens...

A map showing the Lyrid radiant can be found at
http://www.imo.net/calendar/2007 on the website of the International Meteor
Organization.  On the date of maximum, April 22nd, the radiant of the Lyrid
meteors 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.

The Lyrids are a great meteor shower for both beginners and seasoned
observers.  The nights are much warmer now and observing for long periods
of time is quite enjoyable.  If you are new to meteor observing, take out a
lawnchair and sleeping bag and see what it's all about.  If you want to try
recording some meteor data - and help out the meteor researchers and
scientists around the globe - then check out our NAMN Observing Guide at
http://www.namnmeteors.org/guide.html.  We record such information as
the time a meteor occurred, its magnitude (brightness), the shower
it belongs to, its speed, and other comments such as train left behind, or
color.  General information to record includes such things as how dark your
perceived sky is (limiting magnitude), and comments on weather and cloud
cover.  If you have any questions, drop a note to the NAMN Coordinator at
meteors at comcast.net

For visual observers, NAMN has a set of 4 star charts to help you judge the
brightness (magnitude) of the meteors you see.  They are also a great tool
for new observers to help you learn your constellations better.  The charts
can be printed off from http://www.namnmeteors.org/charts.html.  Set your
printer to landscape mode.

Forms to record your observations can be found at
http://www.namnmeteors.org/namn_form.html and
http://www.namnmeteors.org/appendixC.html

Whether you are a beginner or a more experienced observer, get out to
observe the Lyrids.  It's a great shower for rekindling your enthusiasm for
meteors after a long cool winter!


2.  Other April Meteor Activity...

The pi Puppids (PPU) reach a maximum on April 24th at about 3h40m UT.  For
observers in eastern North America, this means about 11.40 pm EDT on April
23rd (4 hours earlier than UT in England).  The duration of the shower is
from April 15th to 28th.  These meteors are slow, with a velocity of about
18 km per second, so will be very distinctive.  At maximum the radiant is
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.  The ZHR rate for the pi Puppids is variable, and has reached as high
as 40 meteors per hour.  A map of the radiant can be found at
http://www.imo.net/calendar/2007.  This meteor shower is 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.  Due to the
latitude of the radiant, this is primarily a southern shower.  According to
the International Meteor Organization, "so far, visual and radio
data have been collected on the shower, but the slow, bright nature of the
meteors makes them ideal subjects for imaging too."

The eta Aquarids (ETA), although not reaching a peak until May 6th, start to
become active about April 19th.  This shower is debris from Halley's Comet.
A common misconception is that Halley discovered this comet.  He did not.
However, his studies led to the realization that previous sightings of it
were all of the same comet - and this led to his name becoming associated
with the comet.  The eta Aquarids are fast meteors with a velocity of about
66 km per second.  ZHR rates at maximum will be about 60 meteors per hour,
but rates in April will be much lower.  A map of the radiant can be found at
http://www.imo.net/calendar/2005/spring

The Antihelion Source (ANT), the ecliptical activity, produces a ZHR of
about 3 meteors per hour with an average velocity of about 30 km per
second.  A map showing the movement of the radiant throughout the month can
be found at http://www.imo.net/calendar/2007

For more info on April showers, and some great reading on historical meteor
observations, check out Gary Kronk's 'Meteor Showers Online' website at
http://meteorshowersonline.com

Besides April's main activity and other minor showers, there is also
sporadic meteor activity.  This sporadic meteor activity is about 7 meteors
per hour visible to the unaided eye.  Some of these are random and some
belong to old untraceable meteor showers.

Planets at midmonth, and their magnitudes, for northern observers, are:
Venus      -3.9   in west in early evening sky
Jupiter    -2.3   in Ophiuchus
Saturn      0.3   in Leo

The phases of the moon for April are as follows:
Mon.  Apr.  2   full moon (smallest of 2007)
Tues. Apr. 10   last quarter
Tues. Apr. 17   new moon
Tues. Apr. 24   first quarter

A useful monthly moon calendar for April can be printed off from
http://stardate.org/nightsky/moon

Note that several planets will appear very close to the moon in the sky this
month, and in some parts of the globe will pass behind the moon:
April 14th - Mars will be 0.5 degrees south of the moon, with an occultation
visible from south and east Asia, India, and the eastern tip of Africa;
April 25th - Saturn will be 1.1 degree south of the moon, with an
occultation visible from Alaska, northwest Canada, the eastern tip of
Siberia, and northern Greenland

Need to know what's happening in the sky right now?  Check out
'SpaceWeather' at http://www.spaceweather.com

For kids (of all ages), NASA puts out a neat space calendar that you can
print off each month.  Check it out at:
http://spaceplace.nasa.gov/en/kids/calendar.shtml

And - need a constellation refresher?  Check out the sky charts on
'Heavens Above' at http://www.heavens-above.com.  Ignore the 'Register' bit.
Just 'Select' your country, then your city, and then scroll down the page to
'Whole Sky Chart'.  Type in what day you want, and pick a time of night.
Pick black on white as it's easier to read and print off.  The maps show the
constellations and the positions of all the visible planets.


3.  International Astronomy Day...

What is Astronomy Day?  Quoting from the Sky and Telescope website at
http://skytonight.com:

"Doug Berger, former president of the Astronomical Association of Northern
California, founded this annual event in 1973 as a high-profile way of
drawing public attention to the science and the hobby through exhibits and
activities at urban centers...  Hundreds of astronomy clubs, observatories,
museums, colleges, and planetariums worldwide now host special
family-oriented Astronomy Day events and festivities."

International Astronomy Day is Saturday April 21 - and Astronomy
Week from April 16th to 22nd.  Groups and individuals around the globe will
be using this opportunity to help spread the word about astronomy - and
about their particular interests in astronomy.  The official Astronomy Day
webpage is hosted by the Astronomical League, at
http://www.astroleague.org/al/astroday/astroday.html

Meteor observers can also help out - and help educate the public about
meteors.  If a local astronomy club is putting on a special event, print off
some information sheets on meteors for them to hand out to the public.
Offer to give a short talk on meteors or meteorites to a local school or
scout group.  Or - contact your local library or bookstore, and offer to
help them set up a display on astronomy.

What free handout material is available for International Astronomy Day?

NAMN has the following handout sheets that we can email you to print off:
"How to Observe Shooting Stars"... a tri-fold, 2-sided brochure
"What are Meteors?"... a summary 1-page version of the brochure
"Surf the Astro Web!"... a list of recommended astro websites
"What's Up Tonight?"... what is visible in the sky on a given night
"What is a Meteor?"... a French info sheet (thanks to Pierre Martin)

Just contact any of the NAMN members listed at the end of this newsletter,
and we will email you copies of the NAMN handout sheets.  They are in Word
format, and you can print off as many copies as you need.

The International Dark Sky Association has great handout sheets on how to
use better lighting for your home... and preserve the Milky Way for your
kids.  A good one to print off for Astronomy Day is "Light Pollution: The
Problem, The Solutions" by D.L. Crawford at
http://www.darksky.org/infoshts/is134.html

International Astronomy Day is a great opportunity to help spread the word
about meteor observing - and how amateur astronomers can help out with real
science.  Get out, get involved - and have fun!


4.  Upcoming Meetings...

June 7-10, 2007, Bareges, France...

The IMC, the International Meteor Conference of the International
Meteor Organization, will be held in Bareges, France from June 7th to 10th.
It is being organized jointly by the IMCCE, Institut de Mecanique Celeste et
de Calcul des Ephemerides, the Paris Observatory, the Observatoire
Midi-Pyrennees and AUDE, l'Association des Utilisateurs de Detecteurs
Electroniques.  This is a gathering for both amateur and professional meteor
observers - and a wonderful opportunity to meet observers from all around
the globe.  Accommodation will be at l'Hospitalet, with talks at the nearby
village cinema.  The registration fee is 120 EUR before May 1st, 130 EUR
after.  The fee includes the conference, all your accommodation, all your
meals, a special excursion to visit the Pic du Midi Observatory in the
Pyrenees - and a conference t-shirt.  For radio observers, there will be a
Radio Meteor School  just prior to the IMC conference.  For more info, check
out the conference website at http://www.imo.net/imc2007

June 11-15, 2007, Barcelona, Spain...

The Meteoroids 2007 conference will be held from June 11th to 15th at the
CosmoCaixa Museum in Barcelona, Spain, organized by the Institut d'Estudis
Espacials de Catalunya.

The preliminary scientific program includes the following sessions:
1. Observational techniques and meteor detection programs
2. Meteor showers' activity and forecasting
3. Orbits of meteoroids and dust
4. Meteoroids' interactions with atmospheres
5. Atmospheric effects induced by meteors
6. Astromineralogy:  properties of meteoroids
7. Interrelationships:  meteoroids - IDPs - dust - micrometeorites -
   meteorites
8. Meteoroid flux and impact hazard
9. Meteor studies in astrobiology

Invited speakers include Diego Janches, Pavel Spurny, Douglas ReVelle, Peter
Brown, Jeremie Vaubaillon, Junichi Watanabe, Peter Jenniskens, P.A. Wiegert,
I. Williams, Olga Popova, Lars Dyrud, John Plane, Nick Mitchel, Frans J.M.
Rietmeijer, Jiri Borovicka, George Flynn, Matthew Genge, Clark Chapman, M.E.
Sansaturio, Jose L. Ortiz, Joseph A. Nuth III, Josep M. Trigo-Rodriguez, and
Alessandra Rotundi.

For more information, check out the Meteoroids 2007 website at
http://www.spmn.uji.es/meteoroids-2007, or contact Dr. Josep M.
Trigo-Rodriguez at trigo at ieec.uab.es

For information on other astronomy meetings, see: 'International
Astronomy Meetings List' at http://cadcwww.hia.nrc.ca/meetings


5.  For more info...

NAMN email: namn at namnmeteors.org
NAMN website: http://www.namnmeteors.org

Mark Davis, meteors at comcast.net
Goose Creek, South Carolina, USA
Coordinator, North American Meteor Network

Cathy Hall, chall at cyberus.ca
Ottawa, Ontario, Canada
Writer, NAMN Notes

Lew Gramer, dedalus at alum.mit.edu
Homestead, Florida, USA
Coordinator, Public Outreach
Owner/Moderator, 'MeteorObs'

Kevin Kilkenny, namnfireball at earthlink.net
Staten Island, New York, USA
Coordinator, Fireballs and Meteorites

Back issues of NAMN Notes can be found online at the NAMN website and in
the MeteorObs archives at:
http://www.meteorobs.org by selecting 'Browse Archive by Month'

To subscribe to the meteor email list:
Contact Lew Gramer at: dedalus at alum.mit.edu

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Here's to 'Clear Skies' for April...

April 2007 NAMN Notes
written by Cathy Hall & edited by Mark Davis
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