What's Up in Space -- 19 Nov 2001

Leonids 2001 Meteor Gallery

METEOR STORM

The display began on Sunday morning, Nov. 18th, when Earth glided into a dust cloud shed by comet Tempel-Tuttle in 1766. Thousands of meteors per hour rained over North America and Hawaii. Then, on Monday morning Nov. 19th (local time in Asia), it happened again: Earth entered a second cometary debris cloud from Tempel-Tuttle. Preliminary reports from China, Korea and Japan indicate 2,000 to 6,000 meteors per hour -- possibly more -- falling over east Asian countries and Australia.

ESA

19 November 2001

Leonids over the Carribean: an on-the-spot report

Read our on-the-spot report from our correspondant in the Carribean.

TELLINGEN

Een tweede piek met een uurfrequentie van ongeveer 2000 in het zenit werd waargenomen in Australië:
Leonids Flux Measurements from Alice Springs, Australia

Zondag 18 november 2001

FOTO'S VAN DE LEONIDEN

Gemaakt met een Olympus E20 op statief en draadontspanner. Belichtingstijd: 25 seconden. Gevoeligheid ISO 80, wit licht gebalanceerd 6500K, diafragma F/2.0. Met Photoshop dark frame reduction toegepast om ruis te onderukken.

Opnametijd: 4:15 - 6:00 EST

Copyright 2001: Andrew Chatman

LEONIDEN-WEERBERICHTGEVING

Leoniden-weerbulletin nr. 4 van Jacob Kuiper

De verwachting voor vannacht, zondag op maandag 18 op 19 nov 2001.

Nederland:

België:

Gebied 2: Het midden en westen van België, ruwweg het gebied tussen de steden Kortrijk-Luik-Sankt Vith-Charleroi.
De grootste opklaringen zijn hier aan het begin van de avond te vinden. Naarmate de tijd verstrijkt draait de stroming in de onderste luchtlagen wat meer naar het noordoosten waardoor wolkenvelden (aangevoerd uit Nederland en Duitsland) weer wat terrein kunnen winnen.

Gebied 3: Het zuidoosten van België, ruwweg het gebied tussen Charleroi - Sankt Vith - Arlon PLUS Groothertogdom Luxemburg:
Aanvankelijk vrij grote velden cirrus en hoge altocumulus maar weinig lage bewolking. Er is een kans dat zich in de opklaringen her en der vanavond wat mist kan vormen. Toch blijven er waarschijnlijk ook wel flinke opklaringen voorhanden. Wil men wat meer zekerheid om de lage wolken te vermijden dan zal men de hoogste toppen in het terrein op moeten zoeken. Enkele Ardense toppen zouden misschien toerikend zijn maar zeker is dit niet. De wolkenbasis in het aangrenzende gebied ligt soms rond de 800 meter en dat is dan net te hoog. Eventueel kunnen de toppen van de Hunsruck en Taunus iets meer garantie geven om boven de wolkendeken uit te komen.

ZW- Duitsland, Rijnvallei tot Bazel:

Noordwest Duitsland:

Verversing van dit bulletin:

Het was oorspronkelijk de bedoeling om in de loop van de avond nog een update van dit weerbulletin te verstrekken. Aangezien de weercondities in Nederland tamelijk slecht lijken te zijn heb ik zelf besloten toch een korte "uitwijkactie" te ondernemen, richting Luxemburg of vlak ten oosten daarvan.

De zeer spectaculaire waarnemingen die van de 1e Leonidenpiek van vanochtend 10 UTC binnenkomen, duiden er op dat de meteoor-voorspellingen goed lijken te kloppen. Wellicht is de 2e piek, waarvan we in West Europa zelf niets kunnen zien, ook goed berekend. Mogelijk dat rond middernacht toch een mooi aantal Leoniden is te verschalken in de dalende flank, achter het tweede maximum. Dat laatste wil ik toch zelf gaan checken en daardoor zal ik helaas geen nieuwe info via dit medium kunnen verstrekken. Ik hoop dat ik u met de weerbulletins enigszins heb kunnen helpen bij uw plannen, helaas het weer werkte niet echt goed mee maar daar kan ik ook niets aan doen.

Jacob Kuiper
hoofdmeteoroloog KNMI, De Bilt.
auteur van Wat een weer!

18 november 2001

LEONIDEN IN ZEELAND

Verslag LEONIDEN waarneming 17/18 november 2001

Inmiddels was ook Nadia Berkelder, verslaggeefster bij de Provinciale Zeeuwse Courant, gearriveerd. Ook zij was benieuwd of er nog wat waargenomen kon worden. Het bleef echter bewolkt. Toen zij vertrok doken we in onze slaapzakken en keken we naar boven. Tegen de bewolking aan. Erik gaf de moed op. Hij had geen vertrouwen meer in het weer en ging weer terug naar Middelburg. De rest zette door, en met succes!
Tussen 02:20 en 04:15 (Ned. Tijd) keken we naar een vrijwel onbewolkte hemel. Daarna trok het weer helemaal dicht.
In de tijd dat we tegen een vrijwel wolkenloze maar wel erg vochtige, hemel keken vielen er enkele tientallen meteoren. Waaronder het pronkstuk van de avond: Een -5 Leonide met nalichtend spoor en fragmentatie, net ten zuiden van sterrenbeeld Gemini. Het nalichtende spoor bestond uit 2 delen.

Om 04:15 trok het weer helemaal dicht en besloten we een pauze in te lassen in de hoop dat het misschien nog op zou klaren. Helaas gebeurde dit niet. Toch waren we gezien de omstandigheden zeker niet ongelukkig. In totaal telden we 59 meteoren, waaronder 52 Leoniden. Verreweg de meeste Leoniden waren behoorlijk helder: Zo tussen magnitude -1 en + 1.

Rijk-Jan Koppejan
Volkssterrenwacht "Philippus Lansbergen" Middelburg

What's Up in Space -- 18 Nov 2001

Leonids 2001 Meteor Gallery

MORE METEORS

METEOR BLAST

GLOBAL LEONIDS

Waarnemingstips/waarnemingscampagnes:

Leoniden 2001: buitenland wacht spectaculaire vertoning

De Leoniden ontlenen hun naam aan het sterrenbeeld Leeuw (Latijn: Leo) waarvandaan ze langs de hemel lijken weg te schieten. Ze zien eruit als razendsnelle, sterachtige puntjes die wegvluchten en worden in de volksmond ook wel 'vallende sterren' genoemd. In werkelijkheid zijn het geen sterren maar stof- en gruisdeeltjes ('meteoroïden') die de komeet 55P/Tempel-Tuttle tijdens zijn vele omlopen rond de zon achterliet. De gruisdeeltjes hebben zich langs de hele baan van de komeet verspreid en de aarde kruist die baan ieder jaar rond 17 november. Terwijl onze planeet door de gruisdeeltjes ploegt, schieten sommige met grote snelheid de atmosfeer binnen. De luchtmoleculen worden door de wrijving met het deeltje zodanig verhit, dat ze fel oplichten. Voordat het deeltje op zo'n 100 kilometer hoogte is verdampt, is zo een langgerekt lichtspoor te zien in de vorm van een meteoor.

In gewone jaren zijn er maar tientallen Leoniden-meteoren per uur te zien. Maar soms zijn het er vele duizenden per uur en is er sprake van een 'meteorenregen'. Het spannendst van de Leoniden-meteorenregens is dat ze onvoorspelbaar zijn. Zo werden Amerikaanse waarnemers in november 1966 verrast toen 150.000 meteoren per uur langs de hemel schoten. Al eerder waren Leoniden-regens te zien geweest in 1799, 1833 en 1866. Aan de hand van de 33-jaarlijkse periode kon toen worden afgeleid dat de meteoren samenhingen met de al eerder genoemden moederkomeet die eens per 33 jaar om de zon scheert. Maar omdat het spektakel in 1899 en 1933 uitbleef, waren weinig waarnemers er in 1996 op bedacht.

Op 28 februari 1998 scheerde de Leoniden-komeet opnieuw langs de zon. Daardoor trekt de aarde nu nog door hoge stof- en gruisconcentraties van de komeetstaart. Meteorendeskundigen voorspelden voor 1998 en 1999 'superuitbarstingen'. In 1998 werden 'slechts' 250 meteoren per uur waargenomen. Maar in 1999 deed zich een opvlamming tot 2700 meteoren per uur voor. Ruimtevaartorganisaties waren zelfs bevreesd dat satellieten door de meteorenstorm zouden worden gezandstraald. Voor alle zekerheid werden kostbare instrumenten zoals de Hubble-ruimtetelescoop van de storm afgewend. Gelukkig deden zich toen geen ongelukken voor. Wel registreerden sterrenkundigen lichtflitsen op de maan. Die werden veroorzaakt door in de maanbodem inslaande Leoniden. In 2000 viel de activiteit weer tegen met een maximale ZHR (aantal meteoren per uur in het zenit) van 480.

Is er een kans dat dit jaar wél een meteorenregen optreedt? Dat hangt er vanaf door welk deel van de zwerm de aarde dit jaar trekt. Op grond van een analyse van de waarnemingen van de vorige jaren is nu een beter inzicht verkregen in de verdeling van de zwerm. Op grond daarvan is de volgende voorspelling uitgebracht voor twee kort na elkaar optredende maxima:

Omdat het in het eerste geval voor ons overdag is, en in het tweede geval de Leoniden-radiant (het vluchtpunt van waaruit de meteoren aan de hemel lijken weg te schieten) zich nog onder de horizon bevindt (opkomst pas om 23.30 u. lokale tijd) ^*, zou dat betekenen dat wij het spektakel moeten missen. Vandaar dat Nederlandse expedities zijn vertrokken naar de VS en China, waar het wél nacht zal zijn én de radiant hoog aan de hemel staat.

Maar: kijk wel als het helder is gedurende de nachten van 17/18 en 18/19 november! Niets is zo onvoorspelbaar als dit soort verschijnselen en de kans dat door een lokale verdichting in het meteoroïdenspoor op een onvoorspeld tijdstip verhoogde activiteit kan optreden, is niet denkbeeldig. De maan stoort dit jaar niet. Het is drie dagen na nieuwe maan zodat de maan al lang onder is als de meteorenactiviteit begint.

Het is dit jaar trouwens de laatste keer dat we iets bijzonders met de Leoniden kunnen verwachten. Volgend jaar is er misschien nog verhoogde activiteit. Maar het is dan bijna volle maan zodat veel zwakkere meteoren in het maanlicht verloren zullen gaan. De jaren daarna neemt de activiteit nog verder af tot een matige zwerm van zo'n 15 meteoren per uur. In 2006 en 2007 zou nog een korte opvlamming kunnen optreden. Maar de modellen voorspellen dat het daarna rustig zal zijn omdat Jupiter de banen van de meteoroïden dusdanig zal verstoren dat ze in 2033 en 2066 te ver van aarde zullen passeren.

Carl Koppeschaar

^*) Daniel van Os tekent hierbij aan:

Het is theoretisch mogelijk dat meteoren zichtbaar zijn bij een radiant hoogte van -10 graden. (The Meteor Meniscus: Meteor Distance versus Meteor Zenith Angle, James Richardson, Journal of the AMS, June 1999 (No. 4))

Het moet echter wel een vuurbol zijn wil je hem een beetje kunnen zien, de uitdoving is in dit geval bijna 8 magnituden.

Ik ben momenteel bezig met een programma dat waarnemers ondersteunt bij het plannen van een meteorenwaarneming. De Lm(Z) waarde is de geschatte grenshelderheid in het zenit. Bij de bepaling hiervan wordt rekening gehouden met de positie van de maan en de zon, de fase van de maan (inclusief correctie voor oppositie en glare), de zonnecyclus, rayleigh-, waterdamp- en aerosolscattering, temperatuur, vochtigheid, leefdtijd en ervaring van de waarnemer en nog wat zaken. De voorspelling heeft een 20% foutmarge, als de invoerparameters zo goed mogelijk zijn ingevuld. Mijn programma gebruikt een aantal gemiddelden, waardoor de fout groter kan zijn. Je ziet in elk geval mooi het verloop van Lm gedurende de nacht.

Voor de nacht van 17 op 18 november is dit de output:

--------------------------------------------------------------
Nightly Meteor Forecast
Lattrop, Overijssel, The Netherlands, 2001/11/17 to 2001/11/18
(all times are local times)

Local Conditions

Time Event                          Lm(Z)
16:36 Sun Set                        -0.0
17:15 Civil Twilight End             +3.4
17:56 Nautical Twilight End          +5.2
18:10 Moon Set                       +6.2
18:37 Astronomical Twilight End      +6.5
00:00 Local Midnight                 +6.6
05:58 Astronomical Twilight Begin    +6.5
06:38 Nautical Twilight Begin        +5.2
07:20 Civil Twilight Begin           +3.4
07:59 Sun Rise                       -0.0

Tonight at 17:56 nautical twilight will end. At that time the moon
will still be above the horizon. It will set at 18:10 leaving you with
12.5 hours of darkness until 06:38 when the nautical twilight will
begin.

Meteor Activity

Stream (midnight) ZHR RA DEC 
Leonids                14.0   10h18m  +22°07'
Taurids                 3.5   03h32m  +19°40'
Puppids/Velids          1.3   07h41m  -36°10'
Zeta Puppids            1.1   08h00m  -42°55'

Tonight the Leonids will be active. At midnight their ZHR is expected
to be between 10 and 18. The radiant is then located at RA: 10h18m,
dec: +22°07'. The radiant will rise at 22:50 and set at 15:16. It will
transit at 07:01 at an altitude of 60 degrees. At the start of
nautical twillight the radiant will be 59 degrees above the horizon.
From your location you can then expect to see 2 to 3 meteors per hour.
 At the beginning of the astronomical twilight at 05:58 the visible
rate could be between 9 and 16 meteors per hour.
 
--------------------------------------------------------------

Bij deze rates houd ik geen rekening met outbursts, dit verhaaltje is gebaseerd op de gemiddelde jaarlijkse activiteit. De vermelding van de rates bij de doorgang heeft weinig zin, omdat het dan al begint te schemeren, maar zoals gezegd: het programma is in ontwikkeling.

Wat de extra activiteit in Nederland betreft, dat hangt af van de voorspeller.

Het model van Brown/Cook voorspeld voor Amsterdam tussen 00:30 en 2:15 8 meteoren per kwartier extra, dat van Jenniskens 4 extra tussen 2:15 en 4:15. De modellen van Asher/McNaught en Lyytinen/Van Flanderen voorspellen geen extra activiteit voor Amsterdam.

De hier genoemde rates gelden voor een donkere hemel (Lm = 6.5) en voor de op dat moment geldende radiant hoogte.

Daniel van Os

De Leoniden Expeditie 2001

18 september 2001

Nederlanders wederom naar China voor een sterrenregen!

In 1999 waren de Leoniden weer te zien, dit keer vanuit Spanje. De aantallen liepen toen op tot wel 5000 meteoren per uur! Ook dit jaar is er een grote kans op veel vallende sterren. Helaas valt Europa weer buiten de boot, en daarom zullen twee teams van de Dutch Meteor Society (DMS) in november afreizen naar China en Amerika, om getuige te zijn van dit hemelse spektakel. Ook dit jaar trekt de Aarde namelijk weer door enkele stofbanen van de komeet Tempel-Tuttle.

In China zelf zullen 100 km ten noorden van Beijing 2 posten worden ingericht met geavanceerde video, foto en radio apparatuur om de Leoniden te verschalken. Dit alles bij een temperatuur die ver onder het vriespunt ligt. De waarnemers in de VS zullen hun lokatie kiezen in Arizona en New Mexico. De waarnemingen van de DMS zijn van groot belang om een beter inzicht te krijgen in het gedrag van stofdeeltjes in de ruimte, en hoe de Aarde te beschermen tegen inslagen van grote meteorieten uit het heelal. De waarnemingen worden o.a. gepubliceerd in vakbladen als Astronomical Journal en Astronomy and Astrophysics. De Chinese expeditie zal net als in 1998 nauw samenwerken met Chinese wetenschappers van het Astronomisch Observatorium van China (NAOC).

Meer informatie kunt u vinden op: www.dmsweb.org

What's Up in Space -- 17 Nov 2001

NASA TV

GLOBAL LEONIDS

ESA

16 November 2001

The Leonids meteor shower - best one yet?

This year's Leonid meteor shower may well be one to remember. Astronomers are predicting a storm of meteors, or shooting stars, perhaps up to 15000 per hour on the night of 18-19 November, and spacecraft operators are standing by. Unfortunately, for those of us in Europe the Leonids will be below the horizon at that time. ESA scientists have gone 'down under' to catch the light show.

Full story

November 15, 2001

ESA: Leonids 2001 - The Adventure Down Under

Operation Leonids Meteor Storm:
ESA Scientists Search For Shooting Stars In The Southern Hemisphere

In addition to their studies of the meteor shower, the team intends to test a new prototype of an instrument that is being developed for future planetary missions to Mars, Mercury and the Moon.

Over the next few weeks, their adventures and discoveries will be posted on the ESA science web site. In the meantime, read about why they are going to Australia and what they intend to do there.

Visit this special feature at: http://sci2.esa.int/leonids/leonids2001/

NASA Headquarters, Washington, DC

Nov. 14, 2001

NASA LEONIDS ACTIVITIES: SLEEPYHEADS MAY MISS SPECTACULAR CELESTIAL DISPLAY

"It's time to set your alarm clocks and get yourself out under a dark sky," said Dr. Donald Yeomans, head of NASA's Near Earth Object program office, at the Jet Propulsion Laboratory, Pasadena, Calif. "This could be the last opportunity for watching an impressive meteor storm in a dark sky for decades to come."

Meteors, also called shooting stars, are really streaks of light that flash across the sky as bits of dust and rock in space collide with the Earth's upper atmosphere and vaporize. The Leonid shower appears every year around Nov. 17 or 18 as the Earth intersects the orbit of comet Tempel-Tuttle and runs into streams of dust shed by the comet. Best viewing times this year are predicted to be the early morning hours of November 18, with the peak activity expected around 5 a.m. EST.

They are called Leonid meteors for the direction in the sky from which they appear to originate -- the constellation Leo. Because the stream of comet dust hits the Earth almost head- on, the Leonids are among the fastest meteors around -- they zip silently across the sky at 44 miles per second. Every so often, the Earth passes through an especially dense clump of dust from Tempel-Tuttle, and a truly spectacular meteor storm occurs -- the great Leonid storm of 1966 produced 150,000 meteors per hour.

Four NASA centers -- Marshall Space Flight Center, Huntsville, Ala.; Goddard Space Flight Center, Greenbelt, Md.; Ames Research Center, Moffett Field, Calif.; and the Jet Propulsion Laboratory, Pasadena, Calif. -- have activities scheduled around this year's meteor shower.

At Marshall, researchers will use special cameras to scan the skies and report meteor activity around the clock Nov. 17 and 18. From six key points on the globe, they will record and transmit their observations to Marshall's Leonid Environment Operations Center, a data clearinghouse that will provide meteor updates in near real-time through: SpaceWeather.com -- a Web site sponsored by science@nasa.gov.

"We're collecting this data to analyze and refine our meteor- forecasting techniques," said Dr. Rob Suggs, the Leonid Environment Operations Center team leader. "If we can better determine where, when and how the meteors will strike, we can take protective measures to prevent or minimize damage to our spacecraft."

The researchers, along with colleagues from the University of Western Ontario in Canada and the U.S. Air Force, will monitor the storm from six locations, Huntsville, Ala.; Eglin Air Force Base, Fla.; Maui, Hawaii; Sunspot, N.M.; the U.S. Territory of Guam; and the Gobi Dessert in Mongolia. Each location was selected based on meteor forecasts and the area's climate.

The monitoring team also has the capability to detect meteors the casual observer may miss. Using special image-intensified cameras that can detect faint objects even in low-light conditions, the researchers will monitor the shower, using the video screens as windows to the skies. Every hour, the teams will relay their observations to the Marshall control center, helping to paint a comprehensive picture of the meteor storm.

Most Leonid particles are the size of dust grains, and will vaporize very high in the atmosphere, so they present no threat to people on the ground or even in airplanes. However, there is a slight chance that a satellite could be damaged if it were hit by a Leonid meteor. The meteors are too small to simply blow up a satellite. However, the Leonids are moving so fast they vaporize on impact, forming a cloud of electrified gas called plasma. Since plasma can carry an electric current, there is a risk that a Leonid-generated plasma cloud could cause a short circuit in a satellite, damaging sensitive electronic components.

Goddard Space Flight Center is responsible for controlling many satellites for NASA and other organizations and is taking precautions to mitigate the risk posed by the Leonids. These include pointing instrument apertures away from the direction of the Leonid stream, closing the doors on instruments where possible, turning down high voltages on systems to prevent the risk of a short circuit, and positioning satellites to minimize the cross-section exposed to the Leonids.

Goddard controls or manages 21 satellites in the earth and space sciences. It also manages NASA's Tracking and Data Relay Satellite System constellation, which is controlled from White Sands, N.M.

At Ames, meteor experts Dr. David Morrison, chief scientist at NASA's Astrobiology Institute, and Dr. Scott Sanford, a NASA planetary scientist, will be available Friday, Nov. 16, at Ames for media interviews about the Leonid meteor storm. The scientists will discuss NASA's airborne mission to study the Leonids, the danger the meteors could pose to satellites, recent Leonid prediction models and the latest research, which suggests that meteors may have played a role in the origin of life.

On Nov. 18, a team of 19 astrobiologists from five countries will depart from southern California's Edwards Air Force Base on an NKC-135 research aircraft to keep an eye on the sky for satellite operators and to study the processes that may have jump-started life on Earth. The 418th Flight Test Squadron at Edwards Air Force Base operates the research aircraft, which flew previous Leonid Multi-instrument Airborne Campaign (MAC) missions in 1998 and 1999 over Japan and Europe.

Many scientists think meteors might have showered the Earth with the molecules necessary for life's origin. "We are eager to get another chance to find clues to the puzzling question of 'What happens to the organic matter brought in by the meteoroids?'" said Dr. Michael Meyer, lead scientist for astrobiology at NASA Headquarters, Washington, which is sponsoring the airborne observing mission.

Astrobiology is the study of the origin, evolution, distribution and future of life in the universe. Ames is NASA's lead center for astrobiology and the location of the central offices of the NASA Astrobiology Institute, an international research consortium.

Information about the Leonid Multi-instrument Airborne Campaign (MAC) and live Leonid coverage are available at: http://leonid.arc.nasa.gov/ or http://www-space.arc.nasa.gov/~leonid/

Observers can calculate local meteor rates using their home computers via: http://www-space.arc.nasa.gov/~leonid/estimator.html.

The Jet Propulsion Laboratory (JPL) will host a webcast with Yeomans explaining what the Leonids are and how to see them on the JPL Web site

NASA TV will broadcast live commentary and video of the Leonids from 12:30 a.m. to 6 a.m. EST Sunday, Nov. 18. The broadcast, originating from Marshall, will feature live video of the Leonids meteor shower provided by a video camera with enhanced images and animation. If weather and cloud cover inhibit observation, the broadcast will be cancelled and regular programming resumed.

Marshall Space Flight Center News Release

Nov. 13, 2001

Across the globe and around the clock, NASA engineers to track and share Leonids data

From six key points on the globe, they will record and transmit their observations to the Marshall Center's Leonid Environment Operations Center - a data clearinghouse that will provide meteor updates in near real-time intervals through the NASA Web site: SpaceWeather.com, a website sponsored by science@nasa.gov.

Led by the Engineering Directorate at the Marshall Center, the effort is part of a long-term goal to protect spacecraft such as NASA's Chandra X-ray Observatory from dazzling - but potentially damaging - meteoroids. "We're collecting this data to analyze and refine our meteor forecasting techniques," said Dr. Rob Suggs, the Leonid Environment Operations Center team leader. "If we can better determine where, when and how the meteors will strike, we can take protective measures to prevent or minimize damage to our spacecraft."

Those protective measures can range from turning a satellite so its most sensitive surface faces the direction of minimal exposure, to shutting down a spacecraft's electronic operations until the storm has passed.

"Good planning is essential, because in many cases, your only opportunity to protect the spacecraft is before the first meteor strikes," Suggs said. "For example, Chandra's orbit takes it one third of the way to the Moon, and its flight plans are uploaded days ahead of time. Once a meteor storm has begun, it's often too late to do anything about it."

Even though today's satellites are engineered to withstand daily meteoroid strikes, the risk of damage is a bit different for high-speed meteoroid streams, according to Dr. Jeff Anderson of Marshall's Engineering Directorate.

"The 'plasma effect' is more important," he said. "When a meteoroid hits a satellite, it can heat the impact site to thousands of degrees Kelvin - rivaling the surface temperature of the Sun. The entire meteoroid is vaporized along with a tiny bit of the spacecraft."

Considering that meteors are only about the size of a grain of sand, their potential for damage can be surprising. Their speed must also be considered. "They're small, but they move very fast - about 45 miles per second (71 kilometers per second)," said Dr. Bill Cooke of the Marshall Center, who -- along with researchers at the University of Western Ontario in London, Ontario -- generated one of the primary meteor forecast models NASA is evaluating.

According to Cooke's forecast, sky-gazers could see up to 1,400 meteors per hour if they are away from city lights, where the sky is dark enough to see the faint, as well as more brilliant, meteors. In the Eastern United States, the shower is predicted to peak near dawn, while in the Western United States, it is expected to peak around 2 a.m. PST.

A Leonid shower happens every year when Earth passes close to the orbit of the Comet Tempel-Tuttle and the debris left in the comet's path. This year it is expected to be exceptionally strong because of the timing and position of the comet tails.

The material crossing Earth's path this year was ejected from the comet at least 100 years ago. Meteor viewers in the United States, for example, will see material ejected from the comet in 1766 - a decade before the country was founded.

The NASA researchers, along with colleagues from the University of Western Ontario and the U.S. Air Force, will monitor the storm from six locations, each selected based on meteor forecasts and the area's climate. Sites include Huntsville, Ala.; Eglin Air Force Base, Fla.; Maui, Hawaii; Sunspot, N.M.; the U.S. Territory of Guam, and the Gobi Dessert in Mongolia.

Thanks to special equipment, the monitoring team has the capability to detect meteors the visual observer may miss. Using special image-intensified cameras that can detect faint objects even in low-light conditions, the researchers will monitor the shower, using the video screens as windows to the skies. Every hour, the teams will relay their observations to the Marshall control center, helping to paint a comprehensive picture of the meteor storm.

Another tool at Marshall's disposal is "forward-scatter radar" - a system built by Suggs, Cooke and Anderson to monitor near-Earth meteoroid activity around the clock.

"Our system is pretty simple," said Suggs. "We use an antenna and computer-controlled shortwave receiver to listen for 67 MHz signals from distant TV stations."

The transmitters are over the horizon and normally out of range. But when a meteor streaks overhead the system records a brief ping - the echo of a TV signal bouncing off the meteor's trail. Like the cameras, this system is capable of detecting meteors too dim to see with the unaided eye.

The Marshall Center has provided Leonid forecast information to dozens of spacecraft operators to help prepare for this year's meteor shower. "More importantly, by comparing the meteor shower predictions to the actual meteor counts, we are laying the groundwork to improve forecasts in the future," said Suggs.

NASA Science News for November 8, 2001

Jaw-dropping Leonids

FULL STORY.

Thursday's Classroom for Nov. 8, 2001

The upcoming Leonid meteor shower could be one of the best in decades. It's an opportunity to impress your students with happenings in the night sky and, perhaps, to transform some TV watchers into life-long sky watchers. Today's episode of Thursday's Classroom features lessons and activities that will build anticipation for the meteor shower and help you prepare to observe it. Visit Thursday's Classroom for details.

Astronomical Society of the Pacific
San Francisco, California

November 1, 2001

Leonid Meteor Shower Could Be One Of Best In History

In the wee morning hours of Sunday, November 18, the Leonid meteor shower might intensify into a dazzling meteor storm, with "shooting stars" continuously blazing trails across the night sky. Viewers across the United States are perfectly positioned to take advantage of the storm, which could be among the most spectacular sky events of the 21st century according to the latest scientific predictions.

The peak in shower activity will occur between 4:00 and 6:00 a.m. EST, or 1:00 and 3:00 a.m. PST on Sunday morning, November 18. "During the peak, people viewing under clear and dark skies could see meteors shooting across the sky at a rate of 1,000 to 2,000 per hour, with flurries of one meteor per second at the peak of the storm," says Robert Naeye, Editor of Mercury magazine, which is published in San Francisco by the Astronomical Society of the Pacific (ASP).

During the predicted storm, Earth will plow through a trail of tiny dust particles left behind by Comet Tempel-Tuttle during its passage through the inner solar system in the year 1767. This comet rounds the Sun every 33.25 years, shedding dust particles as it is warmed by sunlight. Meteor showers occur when Earth passes through debris left behind by comets. But meteor storms occur when Earth passes through particularly dense ribbons of comet debris.

"During a typical Leonid meteor shower, an experienced observer might see about 10 to 15 meteors per hour. But during a storm, that rate climbs to 1,000 or more meteors per hour," says Naeye. "This year's Leonid storm might peak at a rate of up to 2,000 per hour, although it's difficult to pin down a precise number. The rates will rise and fall over a period of two hours."

"Of course, these numbers depend on the accuracy of our predictions. But the predictions have been remarkably accurate in recent years," says ASP member Dr. Peter Jenniskens, an astronomer and meteor researcher at the SETI Institute in Mountain View, California, and author of an in-depth article about meteor science in the November/December 2001 issue of Mercury magazine.

This year's Leonid display has two added bonuses. The Moon will rise during daylight and set six hours before the peak, so the Moon's glare will not obscure fainter meteors. In addition, the peak will occur on a Sunday morning, so many people can sleep in after a long night of skygazing.

If one mentally traces back the trajectory of Leonid meteors, they appear to originate in the constellation Leo (the Lion). Leo rises around midnight, so the shower will be minimal in the hours immediately after sunset. But it will pick up considerably as the night progresses.

The entire United States should enjoy a good shower. Peak meteor rates should occur around 5:00 a.m. EST, 4:00 a.m. CST, 3:00 a.m. MST, and 2:00 a.m. PST. Observers in eastern Asia and the Western Pacific will also enjoy a storm approximately 8 hours later (in the morning hours of November 19, local time), according to the forecasts. For the latest predictions for your local area, visit this website from NASA's Ames Research Center:
http://www-space.arc.nasa.gov/~leonid/estimator.html

Earth will encounter another dense ribbon of Comet Tempel-Tuttle debris in 2002, but under a full Moon. After that, it's over for nearly a century. "It's now or never," stresses Naeye. "People should take advantage of this year's Leonid storm, because astronomers don't think we'll see another storm like this one until the year 2099. We will probably never see a better meteor shower in our lifetimes."

When you see meteors, popularly known as "shooting stars," you're seeing interplanetary dust particles burning up in the atmosphere at altitudes of about 60 to 70 miles. A typical comet dust particle -- known as a meteoroid -- is only about the size of a grain of sand or a pebble when it enters the atmosphere. Larger chunks of comet debris, perhaps up to the sizes of basketballs, sometimes light up the sky as they burn up, which are events called fireballs or bolides. Leonids enter the atmosphere at 160,000 miles per hour, making them the fastest meteors of the year.

"Shooting stars are for every man, woman, and child to see, and it doesn't take any special equipment to see them," says Jane Houston Jones, a member of the ASP Board of Directors and an experienced meteor observer. "Most Leonid meteors are faint, so you'll see more of them if you are far away from city light pollution. If you can't get to a dark site, then control your own light pollution by turning out as many lights as you can control. Then sit back in a lawn chair, bundle up in a blanket, and at a little before midnight local time, face east. You'll see the backwards question-mark shape of Leo's mane rising, and that's where the meteors will appear to radiate over the next few hours."

Meteors are beautiful sky events for skygazers. But for scientists, meteors are fascinating in their own right. "Meteor science involves more than just predicting storms. We also want to learn about the meteoroids themselves, which in turn tell us a great deal about the parent comet," says Jenniskens. "We also want to learn more how meteors may have brought critical organic material to Earth, perhaps leading to the origin and prevalence of life on our planet."

Related Articles:

• Ready for the Storm, by Peter Jenniskens
• How to Enjoy the Meteor Show, by Jane Houston Jones

AstroAlert

The Leonids to Provide an Unforgettable Show in November

For those located in the Americas' the Leonids are predicted to reach maximum activity between 10 and 10:30 Universal Time on Sunday morning November 18th. This corresponds to 5:00-5:30AM EST, 4:00-4:30AM CST, 3:00-3:30AM MST, and 2:00-2:30AM PST. Other peaks are predicted to occur later near 17:30 and 18:15 Universal Times. These later times favor the Eastern Pacific area, Eastern Asia and Australia. Since these areas are located west of the International Date Line it will be important to note that from those locations the meteor shower will occur on Monday morning November 19 local time.

The earth does not begin encountering Leonid meteors before November 10. From November 10-15 the Leonid rates are very low with only 1-2 meteors being seen each morning. Even on the 16th and 17th rates will still be less than 10 Leonids per hour. Not until we approach the times of predicted maximum activity will Leonid rates exceed 100 meteors per hour and hopefully much higher. The process then repeats itself in the opposite order as the earth moves past the main swarm of Leonid meteors. The last of the Leonid meteors appears near November 25. Leonid meteors are not visible until late in the evening when the constellation of Leo the Lion rises in the eastern sky. As Leo rises higher into the sky the chance of seeing more activity increases.

No one knows precisely how many meteors will appear. Experts predict that the maximum activity seen near 18:15 UT will produce the most activity. Let me state that if you are located in any of the areas mentioned above you will most likely witness the most impressive meteoric display to be seen during your lifetime. So this is definitely an event not to be missed! Being on a weekend I would suggest traveling to an adjacent county or state to escape cloudy skies. Your local weather bureau web site provides links to infrared satellite pictures that show the higher clouds at night. This is invaluable resource when trying to find the nearest clear skies.

One should plan to start observing at least one hour before the predicted time of maximum activity just in case maximum activity arrives early. Don't expect to see much activity by strolling outside and simply looking up. Your eyes need time to adjust to the dark. Your neck muscles will also tire quickly. If you wish to see some serious activity you need to lie in a comfortable lounge chair. Unless you are located in the tropics a sleeping bag or heavy blanket would certainly help you remain comfortable. Leonid meteors can be seen in any portion of the sky. It's best to look at least halfway up so that none of your field of view is wasted on the ground. That streetlight located across the street will not help either. Most of the Leonid activity will be dim meteors. To see this display in all its glory you need to get away from all sources of artificial lighting to some safe rural area. Usually the local astronomy club will have a rural site available for observing.

If you wish to do more than just watch, then it is useful to know that scientific data can be obtained by simply counting the number of Leonids and non Leonids seen. The start and ending times should be recorded along with any breaks taken during the observing session. Shower association will be easy as the Leonid meteors will all have parallel paths and come from the same general area of the sky. They will also have a similar velocity as seen within your field of view. Non Leonids (sporadics) can travel in any direction at any velocity. If you are familiar which the magnitude system it is also helpful to list the magnitude of the faintest star you can see in your field of view. Typical urban estimates should be near +5.0. Rural skies are better at +6.0 and higher. If you are really enthusiastic then you may wish trying to record the time and magnitude of each meteor seen. Of course if activity becomes too high then a simple count per minute will suffice.

Meteor reports can be sent to me at: lunro.imo.usa@home.com and to Sky & Telescope at: observers@skypub.com

For more information on observing meteors visit the Sky & Telescope Web Pages at: http://www.skypub.com/sights/meteors/meteorwatch.html

A weekly preview of current meteor activity is also published each Thursday at: http://www.amsmeteors.org/lunsford/

Clear Skies!

Robert Lunsford,
Secretary General of the International Meteor Organization
Visual Meteor Program Coordinator of the American Meteor Society
Meteors Section Coordinator of the Association of Lunar & Planetary Observers

space.com

07 November 2001

Earth Orbiting Satellites Brace for Leonid Meteor Shower

CAPE CANAVERAL, Fla. -- Satellite operators will keep a close eye on their Earth-orbiting spacecraft during the upcoming Leonid meteor shower, and though the risk of damage from a stray speck of dust is greater than normal, officials are confident there will be no natural disasters in space.

Nevertheless, if a Leonid meteoroid hits a satellite, the small grain can destroy an imaging mirror or plow through fragile parts such as an electricity-generating solar panel, possibly creating electrical shorts that can disable the craft. Just the momentum imparted by an impact can throw a satellite off course.

Full story here.

The U.S. Coast Guard Navigation Centre

What's News for November 2001

Annual Leonid Meteor Shower

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