Category: Meteor Showers

Although the peak of the Geminid meteor shower has now passed, that doesn’t mean the activity will stop. For at least another week you’ll spot a rise in random activity that points back to the radiant of this reliable annual display. For most it will only be a bright streak that makes us yell out loud at its sudden beauty, but for some? We want the real dirt. We wanna’ know what’s really going on inside of Phaeton Place…

First noted in 1862 by Robert P. Greg in England, and B. V. Marsh and Prof. Alex C. Twining of the United States in independent studies, the annual appearance of the Geminid stream was weak, producing no more than a few per hour, but it has grown in intensity during the last century and a half. By 1877 astronomers were realizing that a new annual shower was occurring with an hourly rate of about 14. At the turn of the century it had increased to an average of over 20, and by the 1930s to from 40 to 70 per hour. Only ten years ago observers recorded an outstanding 110 per hour during a moonless night.

So why are the Geminids such a mystery? Most meteor showers are historic, documented and recorded for hundred of years, and we know them as being cometary debris. When astronomers first began looking for the Geminids’ parent comet, they found none. After decades of searching, it wasn’t until October 11, 1983 that Simon Green and John K. Davies, using data from NASA’s Infrared Astronomical Satellite, detected an orbital object which the next night was confirmed by Charles Kowal to match the Geminid meteoroid stream. But this was no comet, it was an asteroid.

Originally designated as 1983 TB, but later renamed 3200 Phaethon, this apparently rocky solar system member has a highly elliptical orbit that places it within 0.15 AU of the Sun about every year and half. But asteroids can’t fragment like a comet – or can they? The original hypothesis was that since Phaethon’s orbit passes through the asteroid belt, it may have collided with other asteroids, creating rocky debris. This sounded good, but the more we studied the more we realized the meteoroid “path” occurred when Phaethon neared the Sun. So now our asteroid is behaving like a comet, yet it doesn’t develop a tail.

So what exactly is this “thing?” Well, we do know that 3200 Phaethon orbits like a comet, yet has the spectral signature of an asteroid. By studying photographs of the meteor showers, scientists have determined that the meteors are more dense than cometary material but not as dense as asteroid fragments. This leads us to believe that Phaethon is probably an extinct comet that has gathered a thick layer of interplanetary dust during its travels, yet retains the ice-like nucleus. Until we are able to take physical samples of this “mystery,” we may never fully understand what Phaethon is, but we can fully appreciate the annual display it produces.

But I promised you dirt, didn’t I? Then let’s take an even better look at “Phaeton Place”…

If you happened to catch one of these bright meteor displays, you may have noticed it seemed to hang around a little bit longer. There’s good reason for that. The speed at which them Geminids hit our atmosphere is around 80,000 mph, about half that of the mighty Leonids. So what can cause that? Let’s ask meteor expert Wayne Hally.

“There are three factors which combine to create a meteor’s starting speed in the atmosphere. The minimum speed is around 11 kilometers per second…this is due solely to the Earth’s gravity. A particle that has a speed of zero relative to the Earth, will be drawn in by gravity until it is traveling just over 11kps when it reaches meteor height (~100km). The second factor is the particle’s motion around the Sun, and can range up to 42 kps at the Earth’s orbital distance. Anything moving faster is not in orbit around the Sun, and is either passing through the solar system or has been accelerated by interaction with a solar system object and is on it’s way out. These are VERY rare. Meteor shower particles must be in orbit, since we pass them as our orbits intersect each year.” says Halley. “Finally there is the Earth’s motion around the sun..we are moving around 30 kps in our own orbit, so we are adding our own motion to that of the particle around the Sun. So showers with slow speeds (< 30 kps) are catching up to us from behind. Meanwhile, the fastest showers, such as the leonids, are moving at high speed in a retrograde orbit (opposite that of the Earth) and smash into our windshield (the atmosphere) at the highest speed. (~72 kps). (BTW, the theoretical fastest speed is not 72+30+11 kps, rather it is about 72.9 kps...the speeds are not added directly....it is the square root of the sum of the squares....to explain it simply, a particle moving 72 kps has less time to be accelerated and only reaches 73, while a particle whose speed is zero has lots of time to be accelerated by gravity so winds up at 11 kps)." Want even more dirt? The Geminid meteor shower rate has been continually increasing as well. “The Geminids are strong-and getting stronger,” says Bill Cooke of NASA’s Meteoroid Environment Office. Just like a giant vacuum cleaner sucking up the dirt from our homes, so Jupiter has been busy attracting the meteoroid stream and drawing it closer and closer to Earth’s orbit. Meteor expert Peter Brown of the University of Western Ontario (UWO) says the trend could continue for some time to come. “Based on modeling of the debris done by Jim Jones in the UWO meteor group back in the 1980s, it is likely that Geminid activity will increase for the next few decades, perhaps getting 20% to 50% higher than current rates.”

Eventually this annual meteor shower could become a regular fireball showcase! And we’ll all be watching Phaeton Place…

Image Credits: Geminid Still Shots and Video – Courtesy of John Chumack, Geminid Still Photo – Courtesy of Haplo, Phaeton Orbit Plot – Courtesy of Randy Russell (UCAR), Geminid Meteor Rate Chart – Bill Cooke, NASA Meteoroid Environment Office. We thank you so much!

The annual Leonid Meteor Shower is about to light up the night… And the time to start watching is now. The year 2009 will not see a Leonid storm, but an outburst for sure. There are still some uncertainties regarding the time of maximum of the 1466 trail. For those of you seeking a definitive date and time, it isn’t always possible, but we can learn a whole lot about when and where to look.

The Leonid Meteor Shower belongs to the debris shed by comet 55/P Tempel-Tuttle as it passes our Sun in its 33.2 year orbit. Although it was once assumed it would simply be about 33 years between the heaviest “showers,” we later came to realize the debris formed a cloud which lagged behind the comet and dispersed irregularly. With each successive pass of Tempel-Tuttle, new filaments of debris are left in space along with the old ones, creating different “streams” the orbiting Earth passes through at varying times, which makes blanket predictions unreliable at best. Each year during November, we pass through the filaments of its debris – both old and new ones – and the chances of impacting a particular stream from any one particular year of Tempel-Tuttle’s orbit becomes a matter of mathematical estimates. We know when it passed… We know where it passed… But will we encounter it and to what degree? Traditional dates for the peak of the Leonid meteor shower occur as early as the morning of November 17 and as late as November 19.

So what can we expect this year? According to NASA’s 2009 predictions a significant shower is expected this year when Earth crosses the 1466-dust and 1533-dust ejecta of comet 55P/Tempel-Tuttle. According to J. Vaubaillon, the narrow (about 1-hr) shower is expected to peak on November 17, 2009, at 21:43 (1466) and 21:50 (1533) UT, perhaps 0.5 to 1.0 hour later based on a mis-match in 2008, with rates peaking at about ZHR = 115 + 80 = 195/hr (scaled to rates observed in 2008). E. Lyytinen, M. Maslov, D. Moser, and M. Sato all predict similar activity from both trails, combining to about ZHR = 150 – 300 /hr. P. Jenniskens notes that if the calculated trail pattern is slightly shifted in the same manner as observed before, then the 1533-dust trail would move in Earth’s path and its rates would be higher (the 1466-dust trail would move away). However, the 1533-dust trail is distorted in the models, and because of that it is not clear how much higher that would be. This remains a rare opportunity to study old dust trails from comet 55P/Tempel-Tuttle. In such old trails, the model of Lyytinen and Nissinen predicts wide trails, which can be tested by measuring the width of the outburst profile.

Let’s take a closer look at the at how the two centuries old trails will affect our observing, beginning with the one created in the year 1466. The exact same trail will be encountered again this year with its maximum rate of up to 115 meteors per hour occurring at 21:43 UT (may be 0.5-1hr later). “The trail will be much closer to the Earth, explaining why we expect a quite high zenith hourly rate.” say J. Vaubaillon (et al), “However the discrepancy between the expected time of maximum remains, as well as a general higher expected ZHR. Among the possible explanations are: sensitivity to initial conditions (given that the trail is 16 Rev. old) or change of cometary activity (impossible to verify unfortunately).”

But don’t count on only this single trail, because the year 1533 trail will encounter the Earth at almost the same time as the 1466 trail. Its maximum time of arrival is expected to be at 21:50 UT on the 17th of November, with a zenith hourly rate of 80 – for a combined rate of perhaps 200 meteors per hour. “The total level of the shower (ZHR~200/hr) was callibrated using the 2008 observations of the 1466 trail, but nothing is known from the 1533 trail. As a consequence, it will be very interesting to check.” comments Vaubaillon, “In particular there might be a difference of up to 1 hour between the 1466 and 1533 trail, or they might even be late together, giving us some insight about how well/poorly we know comet 55P’s orbit.”

Let’s take a closer look with 3D-view of the two trails may have evolved between 1466 and 2009…

Dr. Vaubaillon’s colleagues from MSFC (D. Moser and B. Cooke) pointed out that the best location to view the outburst caused by the 1466 and 1533 trails will be centered around India and includes: Nepal, Thailand, Western China, Tadjikistan, Afghanistan, Eastern Iran, South Central Russia, etc. Dr. P. Atreya (IMCCE), citizen of Nepal, is currently organizing an international Leonid observation campaign in his home country. This campaign will involve many amateurs and researchers from Nepal and other countries. The climate conditions in Nepal at this time of the year makes it an excellent spot.

We may never know precisely where and when the Leonids might strike, but we do know that a good time to look for this activity is well before dawn on November 17, 18 and 19. Where do you look? For most of us, the best position will be to face east and look overhead. With the Moon out of the picture, even if you don’t see a huge amount of meteoric activity, chances are that even a few minutes of your time will bring a bright and happy reward!

Many thanks to John Chumack for sharing his early 2009 Leonid image and to NASA, Dr. Vaubaillon and colleagues for the illustrations and 3D animation!

It’s not often that both hemispheres of the Earth get treated to an annual meteor shower, but in a matter of hours the complex Orionid stream is heading to dark sky your way! Where and when do you watch? Will it be as good as this year’s Perseids as filmed by John Chumack above? Try even better! Follow me…

We are now slipping into the stream of Comet Halley and one of the finest meteor showers of the year. If skies are clear tonight, this would be the perfect chance to begin observations of the Orionid meteor shower. But get to bed early and rise well before dawn to enjoy one of the year’s most reliable meteor showers. The offspring of Comet Halley grace the early morning hours as they return as the Orionid meteor shower. This dependable shower produces an average of 10-20 meteors per hour maximum, and best activity begins before local midnight on the 20th, and reaches its peak as Orion stands high to the south about two hours before local dawn the 21st. With only the tiniest crescent of a Moon gone in the early evening, this looks to be the year’s premier meteor shower!

Although Comet Halley has now departed the inner Solar System, its debris trail remains well organized – allowing us to predict when this meteor shower will occur. The Earth first enters the stream at the beginning of October and does not leave until the beginning of November. This makes your chances of “catching a falling star” above average! These meteors are very fast, and although faint, occasional fireballs do leave persistent trails.

For best success, get away from city lights. Face south-southeast in the northern hemisphere and almost overhead in the southern – then relax and enjoy the stars of the Winter Milky Way. The radiant is near Betelguese, but may occur from any part of the sky. The meteor watching experience is much more comfortable if you include a lawn chair, blanket, and thermos of your favorite beverage.

Orionid Meteor Shower – Key Points

• The nights of October 21st and 22nd are the best times to watch.
• Maximum hours rates are typically 20/hr and meteors are described as “fast”.
• The radiant is at RA=06h20m, DEC=+16o, just above the left shoulder of Orion.
• The average magnitude of an Orionid meteor is 3.

Clouded out? Don’t despair. You don’t always need eyes or perfect weather to keep the watch. Tune an FM radio to the lowest frequency that doesn’t receive a clear signal. An outdoor FM antenna pointed to the zenith increases your chances – but isn’t essential. Simply turn up the static and listen. Those hums, whistles, beeps, bongs, and occasional snatches of signals are distant transmissions being reflected off a meteor’s ion trail!

Sky Chart Courtesy of NASA.

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Within hours, the peak of the annual Perseid meteor shower will begin. If you’re worried you’ll be clouded out, then let’s take a look at a different way that you can observe the activity… without your eyes!

Did you know that you can “listen” to meteor showers? If you’re a ham radio operator, then you prize the ionized trails that meteors leave in our atmosphere to allow further signals to “bounce” to more distant receivers. However, you don’t really need complicated equipment to listen to a meteor shower – just an FM receiver and an external antenna. Even your car radio will work!

Place your radio setting on the lowest frequency that doesn’t receive a clear signal and simply listen to the static. When a meteor passes overhead you’ll hear snatches of radio signals from distant stations, pops, buzzes, pings, shrieks, howls, and simple changes in the white noise. Sometimes it’s subtle – and sometimes it’s striking. One thing is for sure, the noises you hear are definitely out of this world! Your equipment can run the gambit from connecting a genuine outdoor FM antenna to an indoor receiver and recording with a tape deck for later playback, to a portable radio. I’ve even used an old television set connected to an outdoor television antenna tuned to channel 3. It’s all fun – and the results are amazing. Here are the dates for the 2009 Perseids.

To open the public’s eyes to just how easy radio meteor listening can be, astrophysicist Chris Lintott will be doing a presentation live in Trafalgar Square on August 14th, 19-20h BST. Chris is a co-presenter of the BBC’s “The Sky at Night” astronomy programme, and is a lecturer at University College London and the project he’s about to take part in is very unique… The Fourth Plinth.

This summer, sculptor Antony Gormley has invited the world to help create an astonishing living monument. He is asking the people of the UK to occupy the empty Fourth Plinth in Trafalgar Square in London, a space normally reserved for statues of Kings and Generals. They will become an image of themselves, and a representation of the whole of humanity. Every hour, 24 hours a day, for 100 days without a break, a different person will make the Plinth their own.

Because of the appalling levels of light pollution in London, Lintott remembered a radio-meteor demonstration given by Andy Smith of G7IZU Radio Reflection Detection and his friend David Entwistle for “The Sky at Night” a couple of years ago, and wanted to do something along those lines. Since no power or wiring are allowed on the Plinth, Chris will be utilizing a recording done by Andy beginning tonight… a talent he’s quite good at! For every hour from midnight on, G7IZU Radio Reflection Detection will be recording the Perseid event and sending Chris the most active hours as MP3 files. He’ll then play these
to the masses over an amplified speaker while holding up photos of how it all works.

If you’re interested in the live radio-meteor/astronomy demonstration, you can access a live video of the Fourth Plinth – and be sure to join them on August 14th, 19-20h BST for Chris Lintott’s presentation!