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
1. Perseids - The Best of the Summer...
2. Lots of Summer Aquarids...
3. Other August Meteor Activity...
4. The Pleasures of Amateur Astronomy, by Pierre Martin...
5. Upcoming Meetings...
6. For more info...
The hot summer days are upon us here in the northern hemisphere - and the hot summer nights bring one of our favorite annual meteor showers - the Perseids.
This year, this wonderful shower is hampered by a bright moon in the sky - but don't kid yourself. It's still one of the best showers of the year. Why? Because many of the meteors are bright and long and spectacular - and can be seen in spite of the moon.
When is the peak? The Perseids (PER) reach a peak on August 12th this year. Specifically, according to the International Meteor Organization (IMO) “the... maximum is most likely between 23h - 1h30m UT on August 12-13, though other peaks on August 13 around 2h and 9h UT are also possible from recent past results.”
What is UT? This refers to Universal Time in Greenwich, England. For observers in eastern North America, this means 4 hours earlier for EDT. This means between 19h and 21h30m, which in normal clock terms means a peak between 7 p.m. and 9.30 p.m. on August 12th. The other possible peaks on the 13th then become 22h and 5h EDT, and in normal clock terms, 10 p.m. on the 12th and 5 a.m. on the morning of the 13th. To get from UT to EDT, subtract 4 hours, then to translate from the '24 hour' system to normal clock terms, subtract 12 if the hours are over 13.
The Perseids started back about July 17th and last through until about
August 24th. The public often thinks that the Perseids last only for a
couple nights around the 12th - but they actually last for over a month.
The rates are highest in mid-August though. ZHR rates around August 12th
will be about 100 meteors per hour - and rates for a number of days before
and after that date will be quite good as well. The IMO, in their 2006
Meteor Shower Calendar, mentions that “enhanced Perseid activity is possible
this year, though perhaps not as strongly as in 2004... the timing of any
enhancement, though probably not far from the expected
What is ZHR? This refers to Zenithal Hourly Rate, and is the number of meteors that an observer would expect to see in an hour, on average, under a dark country sky, if the radiant, the area in the sky where the meteors seem to come from, is directly overhead. So, to see as many meteors as possible, try to get away from city lights, try to block the bright moon with a tree, and try to observe when the constellation of Perseus is fairly high in the sky.
Where are the meteors? Where do you look? Perseid meteors can be seen anywhere in the whole sky - but if you trace the line of a Perseid meteor back to where it came from, the starting point will be near the constellation of Perseus. To see a map of the radiant, check out http://www.imo.net/calendar/2005/summer. Another thing that the public and beginning observers do not realize is that the radiant, the area in the sky where the meteors seem to come from, actually moves a bit from night to night. You can see this motion indicated on the IMO map.
The Perseids are one of the oldest meteor showers that mankind has records for. The earliest reference to the shower seems to have been in the year 36 A.D. in China. Because the path of the Perseids is highly inclined to the ecliptic, it has not been affected as much over the millennia by the disturbing influences of our major planets that travel basically along the ecliptic path. As a result, the Perseids are a reliable meteor shower, seen in strength each year.
The Perseids were also the first meteor shower to be proven to be associated with a comet. This was found by Giovanni Virginio Schiaparelli (1835-1910), more often remembered for giving the name 'canals' or 'channels' to the markings on the planet Mars. The parent body of the Perseid shower is called Comet 109P/Swift-Tuttle, after its discovery in 1862 by several Americans - Lewis Swift of Marathon, New York and Horace Tuttle of Harvard Observatory, Massachusetts. In late August and early September of that year, the comet reached a magnitude of about 2, about as bright as the stars in the Big Dipper, and it had a tail length of between 25 and 30 degrees, about 5-6 times the distance between the pointer stars of the Big Dipper. The comet comes around to our part of the solar system about every 120 years. In November of 1992, it was seen at about magnitude 5.0.
The magnitude or brightness of the meteors themselves is interesting as well. Studies by Hruska and Ceplecha in the 1950's indicated that the Perseids generally seem to be brighter before the date of maximum activity than afterwards, but that some periods of brighter or fainter meteors do occur. This tends to indicate some filamentary structure in the Perseid meteoroid stream. In other words, we encounter clumps of brighter or fainter meteors as the earth passes through different layers of long-ago debris shed by Comet Swift-Tuttle.
In early Europe, the Perseids came to be known as the 'tears of St. Lawrence'. In an article called 'The Discovery of the Perseid Meteors', on the Sky and Telescope website at http://skyandtelescope.com, Mark Littmann writes:
"Saint Lawrence was tortured and killed in Rome on August 10, 258 during the reign of the anti-Christian emperor Valerian... Citing Quetelet, 'a superstition has 'for ages' existed among the Catholics of some parts of England and Germany that the burning tears of St. Lawrence are seen in the sky on the night of the 10th of August; this day being the anniversary of his martyrdom.' "
Legends abound about Perseus. In ancient Greek mythology, he was a hero - the son of Zeus. On one quest, he took off to slay the famed Medusa, a beautiful mortal lady who had been unceremoniously turned into a fearsome Gorgon by the jealous goddess Athena. Medusa's beautiful hair became a squirming mass of snakes - and her gaze deadly. Perseus traveled with the help of winged sandals from Hermes, the messenger god; a sword of diamond from Hephaestus, the god of fire and the forge; and a magical helmet to make him invisible, from Hades, god of the underworld. He slew Medusa without looking at her by using her reflection in his shield. The blood of Medusa fell to earth and created the great winged horse Pegasus.
On his way home, he rescued the princess Andromeda, daughter of King Cepheus, who was chained to a rock as a sacrifice to the sea monster Cetus because of the vainful boasting of her mother, Queen Cassiopeia. Perseus rescued the fair maiden and married her. And now, in our constellations, we have all the players in the legend. Take a look at your sky. We have Perseus, Pegasus, Andromeda, Cepheus, Cassiopeia, and Cetus - and even the infamous Medusa, immortalized as the 'Demon Star' in the constellation of Perseus.
NAMN has a set of 4 star charts to help you learn these constellations in the sky and to help you judge the brightness (magnitude) of the meteors you see. These can be printed off from http://www.namnmeteors.org/charts.html. Set your printer to landscape mode.
If you want to record data on the Perseids for the meteor researchers, check out our NAMN Observing Guide for information on what to record. The Guide can be found at http://www.namnmeteors.org/guide.html. We record such info 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 our NAMN Coordinator at meteors@comcast.net
Forms to record your observations can be found at
http://www.namnmeteors.org/namn_form.html and
http://www.namnmeteors.org/appendixC.html
The August sky is full of many other meteors besides Perseids - and many of these other meteors are from the constellation of Aquarius.
Or, we should say that they are from the general vicinity of Aquarius. Sometimes a meteor shower may be named after a constellation, but the meteors, if you look closely at a map, might actually come from the border of the constellation next door. And of course, all the radiants move a bit from night to night. Help! Where do you look?
Help is available by printing off the maps on the IMO website at http://www.imo.net/calendar/2006/summer. Also too - if you look at the Aquarid radiants on any given night, you will notice that they form sort of a parallelogram in the sky. This helps in keeping track of them. Mark all your meteor radiants on a map before you go out observing.
The southern delta Aquarids (SDA) reached a peak on July 28th, but can be seen until about August 19th. These are average velocity meteors at about 41 km per second. ZHR rates in July were about 20 meteors per hour, but August rates will be much lower.
The southern iota Aquarids (SIA) reach a maximum on August 4th with a duration from July 25th to August 15th. They are slower than the delta's, with a velocity of about 34 km per second, but still classed as average velocity. At their peak, the ZHR rate will be about 2 meteors per hour.
The northern delta Aquarids (NDA) peak supposedly about August 8th with a duration from July 15th to August 25th. These are average velocity at about 42 km per second, very similar to the southern delta's. At their peak, they supposedly reach a ZHR of about 4 meteors per hour. However, the IMO notes that “the NDA may be a good deal less active than previously thought, and may not be producing a visually definable maximum at present.”
The northern iota Aquarids (NIA) peak on August 20th, but run from August 11th to 31st. They are average velocity as well at about 31 km per second, very similar to the southern iota's. At their peak, ZHR rates will be about 3 meteors per hour. The IMO mentions that observations studied from 1988 to 1995 “could mean their better rates (even so, very weak) happen several days after the suspected peak on August 20.”
For those observers interested in trying something a bit different, the Aquarids are “rich in faint meteors, making them well-suited to telescopic Work” according to the IMO. For those interested in trying meteor work by telescope, instead of just with the unaided eye, check out the telescopic meteors section of the IMO at http://www.imo.net/tele/index.html
For those of you interested in plotting your meteors (recommended for serious observations), special IMO plotting maps can be ordered through Robert Lunsford of the International Meteor Organization. For details, contact him directly at lunro.imo.usa@cox.net
The Pisces Austrinids (PAU) peaked back on July 28th, but can be observed until about August 10th. These are average velocity meteors at about 35 km per second. ZHR rates were about 5 meteors per hour at the peak, but will be lower in August. A map of the radiant can be found at http://www.imo.net/calendar/2006/summer
The alpha Capricornids (CAP) peaked on July 30th, but run until about August 15th. These are wonderful, slow meteors, with a velocity of about 23 km per second. ZHR rates at the peak were about 4 meteors per hour, but again, rates in August will be lower. A map of the radiant can be found at http://www.imo.net/calendar/2006/summer. According to the IMO, in their 2006 Meteor Shower Calendar, the alpha-Capricornids “are noted for their bright - at times fireball-class - events, which, combined with their low apparent velocity, can make some of these objects among the most impressive and attractive an observer could wish for.”
The kappa Cygnids (KCG) reach a maximum on August 18th and can be seen from about August 3rd to 25th. These are almost slow meteors at about 25 km per second. ZHR rates at the peak will be about 3 meteors per hour. A map of the radiant can be found at http://www.imo.net/calendar/2004/summer. The IMO mentions that “occasional slow fireballs from this source have been reported... more data are needed on a shower that is often ignored in favour of the major Perseids during August.”
Lastly, the alpha Aurigids (AUR) start to become active about August 25th, although will not peak until September 1st. These are fast meteors at 66 km per second. ZHR rates at the peak will reach about 7 meteors per hour, but rates in August will be lower. Where is the radiant? Check out http://www.imo.net/calendar/2005/summer. This shower had short unexpected outbursts of about 30-40 meteors per hour in 1935, 1986 and 1994. Please monitor this shower, and send us your observations. The IMO mentions that “telescopic data... would be especially valuable, but photographs, video records and visual plotting would be welcomed too.”
For other minor showers not on the International Meteor Organization, 'Working List of Visual Meteor Showers', and for a wealth of historical information on all showers, check out Gary Kronk's 'Comets and Meteor Showers' website at http://comets.amsmeteors.org
Besides August'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 -3.8 very low in east-northeast in morning twilight Jupiter -2.0 in Libra, very low in west-southwest in evening twilightNote that on Saturday August 26th, at 23h UT, the planet Venus will be 0.07 degrees north of Saturn. This is extremely close in the sky - try to get a look at this!
The phases of the moon for August are as follows:
Wed. Aug. 2 first quarter Wed. Aug. 9 full moon Wed. Aug. 16 last quarter Wed. Aug. 23 new moonA wonderful monthly moon calendar can be printed off from http://stardate.org/nightsky/moon. For the NASA kids' calendar for August, go to http://spaceplace.nasa.gov/en/kids/calendar.shtml
One of the simplest sky charts can be found on the website '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. The maps show the constellations and the positions of all the visible planets.
Summer is also a great time to watch for satellites, and to see the ISS, the International Space Station, pass over. The 'Heavens Above' website tells you where and when to look while you're out observing summer meteors!
The following are excerpts from a posting by Pierre Martin to the Ottawa Valley Astronomy and Observers Group email list. Pierre enjoys observing both deep sky objects with his telescope, and meteors with just a lawnchair and his very wide open eyes. He provides some comments on why summer observing under a dark sky is so inspiring.
"... I've come to realize that one of the reasons I like to head out observing so much is to escape from the hubbub of everyday life - including computers, telephones and electronics.
... Whatever way we choose to pursue the hobby, it's all about an escape into the cosmos - an evasion of the mind - and a way to momentarily forget all our little daily problems. All of a sudden, our personal issues seem so vanishingly small and insignificant when staring up at the vast expanse above. In a constantly changing and fast-paced world, we've come accustomed to the unexpected. It's comforting to find the night skies presenting us constant clockwork and the same 'old friends' reappearing year after year. Few things in life are so reliable as that!
... Star hopping and hunting is an activity I enjoy - I suppose it's a way to help keep the mind sharp and active. Even though there's way too many objects to memorize, I've found that after seeing one object more than once, the process in locating it later on is much easier. By sweeping a star field at low power, I subconsciously recognize some of the star patterns and I end up getting there faster. I try to imagine myself standing there and waiting for the scope to do its slew - and that would bore me to death - I just *need* to push that scope around. It seems to make me feel more useful too! To me, it's simply lots more fun to look through the scope while it's on its way to the planned target... and possibly 'discover' other sights along the way. That's just me.
... If I were to start complicating my observing setup too much, I feel the enjoyment would drop. Don't get me wrong though... just because that's the style of observing I enjoy doesn't mean I don't like seeing what others are up to... And I honestly do believe that... technology has taken a very important place in amateur astronomy - essential to many for their observing and imaging programs. Going back just a few years ago, people could only dream of such advances in technology. We surely live in exciting times! One can't help but to wonder what amateur astronomy will be like in 10 years?
... I am most happy to travel to a distant dark site with nothing but my lawn chair, my coffin and a box of Krispy Kremes so I can settle in to do what I still love best - just looking up!!! Taking in long moments of nature's uninterrupted sights and sounds has always been among the most enjoyable and memorable times for me. A good aurora or major meteor shower is like a religious experience.
... And I can't say enough on the worthiness of travelling out to a good dark sky. Even with the extra time and effort it takes to get there, the quality of observing is dramatically improved! And those lost hours of sleep will be made up with memories and sightings you'd otherwise miss out from hazy skies or city light pollution.
... I'm looking forward with excitement at summer's heightened meteor activity... Here's hoping the weather will cooperate for some productive nights under dark skies!!! "
Pierre provides many nights of valuable observations to our meteor organizations... and in his spare time, helps out with programs to educate and inspire people to get out and look at our night skies. His group's website can be found at http://www.oaog.ca
September 14-17, 2006, Roden, The Netherlands...
The IMC, the International Meteor Conference of the International
Meteor Organization, will be held near Roden in the Netherlands. This is
the annual get-together for both amateur meteor observers and professional
researchers alike. Talks will cover all types of meteor observing - visual,
telescopic, photographic, video, and radio. The registration fee is 120
Euros, and includes the conference, all meals, all accommodation, an
excursion, and a conference t-shirt. Special workshops will be held on
meteor orbit determination and radio meteors from September 11th to 13th,
with a separate fee. Mark Holland on your calendar for September! For more
info, check out http://www.imo.net/imc2006
For information on upcoming astronomy meetings, see: "International Astronomy Meetings List" at http://cadcwww.hia.nrc.ca/meetings
NAMN email: namn@namnmeteors.org
NAMN website: http://www.namnmeteors.org
Mark Davis, meteors@comcast.net
Goose Creek, South Carolina, USA
Coordinator, North American Meteor Network
Cathy Hall, chall@cyberus.ca
Ottawa, Ontario, Canada
Writer, NAMN Notes
Lew Gramer, dedalus@alum.mit.edu
Homestead, Florida, USA
Coordinator, Public Outreach
Owner/Moderator, 'MeteorObs'
Kevin Kilkenny,
namnfireball@earthlink.net
Staten Island, New York, USA
Coordinator, Fireballs and Meteorites
Back issues of NAMN Notes can be found on-line 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 or
to find out information on our weekly chat sessions:
Contact Lew Gramer at:
dedalus@alum.mit.edu