|
Leonid Meteor Shower
With Dr. Glenn Peterson
The Aerospace Corporation
Friday, Nov. 16, 2001; 3 p.m. EST
In the evening of Nov. 17 and the early morning of Nov. 18 the Earth will pass through the remnants of Comet Tempel-Tuttle creating what is known as the Leonid meteor shower. This year the Earth will come in contact with a particularly dirty part of the Tempel-Tuttle trail. Many astronomers believe this will bring about the strongest burst of shooting stars in more than 30 years.
Dr. Glenn Peterson of The Aerospace Corporation will be online from California to take your questions and comments on Sundays Leonid meteor shower, the effect it will have on orbiting spacecraft and meteors in general.
Dr. Peterson received his BS & MS in Aerospace Engineering from San Diego State University. Following 2 years of work at Johnson Space Center for Unisys designing simulations for astronaut training, he entered the doctoral program at the University of Texas at Austin where he received his Ph.D. in 1997. Since then he has worked in the Astrodynamics Department of The Aerospace Corporation on a variety of topics including the Leonid meteor showers, formation flying of satellites, and collision analysis for space traffic control.
The transcript follows.
Editor's Note: Washingtonpost.com moderators retain editorial control
over Live Online discussions and choose the most relevant questions for guests and hosts; guests and hosts can decline to answer questions.
Washington, D.C.:
I have read that the meteors that we will be passing through are from a comet that went by Earth in 1766 and am having a hard time getting my head around this concept. Could you explain it to me?
Dr. Glenn Peterson: The Leonids are generated by the comet Tempel-Tuttle which orbits the Sun once every 33 years. Every time the comet passes close to the Sun, small particles evaporate off the surface. It is these particles that form the meteor stream. However, it takes several hundred years for the particles to disperse throughout the stream. This means that when the comet passes close to the Earth, there will be a much larger concentration of particles than usual that the Earth passes through. However, due to small changes in the comet's orbit, it never passes through the same point exactly twice. As a result, within the larger meteor stream, there will be concentrations, or "filaments", that are the leftovers from earlier comet passages that have dispersed yet. In 1766, the comet passed at its closest point to the Sun, and it will be the filament that was created by this passage that we will come closest to early Sunday morning.
Vienna, Va.:
I am hearing conflicting times about when the meteor shower will be at its height. Why are there conflicting reports? What makes meteor showers so hard to predict?
Dr. Glenn Peterson: There are two main models predicting Leonid behavior this year. One has two very sharp peaks, the first around 5:18 am EST Sunday morning, the second will be about 15 hours later over Australia. The second model does not have the two sharp peaks but instead predicts a higher level of activity over the whole night. Meteor showers are hard to predict because so little is known about these big events. We have plenty of models, but little actual data to confirm or deny the predictions. Mainly, the differences between the predictions for this year lie in how fast the fresh particles disperse. A faster dispersion rate means that the sharp peaks will not occur, a lower dispersion rate means that the whole night will be active.
London, UK:
How will satellites be effected by the barrage?
Dr. Glenn Peterson: Satellites may be affected by the meteor storm in two separate ways: physical damage through impact (like a bullet hitting the satellite), or through electrical damage. Most Leonid particles are very small (pinhead size and smaller). So if they hit a satellite they can punch a very tiny hole through it. However, electrical damage is more likely. The Leonid particles are travelling about 10 times the speed of an orbiting satellite. They are really zipping along. When they hit a satellite, they are most likely to vaporize into a plasma which can have a bad impact on the electronics of the satellite.
Alexandria, Va.:
What is the difference between a meteor and an asteroid? Does the asteroid belt also have meteors in it?
Dr. Glenn Peterson: When astronomers typically talk about asteroids, they are referring to large stony chunks of material that orbit the Sun. A meteoroid is a small particle and can be either stony or icy, depending on whether they came from a asteroid or a comet. A meteor is a meteoroid that has hit the Earth's atmosphere and has created a visual streak that we can see. A meteorite is a meteor that has survived until it has hit the ground.
Arlington, Va.:
Hi Dr. Peterson, and thanks for taking questions today. I live in the Crystal City area, which suffers from a lot of light pollution, but I have a balcony at the very top of Arlington Ridge with a good view of the sky. I really don't want to drive out to the edge of the city to see this meteor shower -- I'd like to be able to just get up and drink coffee on my balcony while I watch the sky. Will I be able to see anything, or will the light pollution block too much of the shower out?
Dr. Glenn Peterson: You're welcome. Its best to watch the Leonids, and any meteors for that matter, as far away from city lights as possible. I live in LA, and the viewing is really tough here. However, if you can see the stars nicely from your balconey (I can't), then you should be able to see the meteors. Many not all of them, but a good chunk.
Rockville, Md.:
Dr. Peterson:
I was wondering what the best time will be on the east coast for viewing the meteor showers? And,in what part of the sky should we be watching?
Thank You!
Dr. Glenn Peterson: There are two models for this years Leonids. The first predicts there will be two peaks, one around 5:18 am EST Sunday morning; the second peak will be over Australia. The second model predicts no sharp peaks but a general increase in activity the whole night. Given that there is a certain amount of uncertainty in these predictions, I would recommend going out around 3-4 am and watching until dawn (East coast time). The part of the sky to watch is to the east/southeast from your location. Watch about halfway or more up the horizon (45 degrees plus). Keep your eyes moving, staring will tire the eyes quickly.
Silver Spring, Md.:
Dear Dr. Peterson:
Will I be able to see them from my backyard or will I need to go to an open field?
Hurrah for astronomy!
Dr. Glenn Peterson: Hurrah!! :) The best location is probably the place that gives you the greatest expanse of the southeastern sky to look at with the lowest amount of light pollution. I would say the open field is better, but if your backyard points the right direction and the neighbor's lights don't get ya, the backyard may be ok.
Sterling, Va.:
Do you know of any local places to observe the meteor shower? Do you have recommendations for photographing meteors?
Dr. Glenn Peterson: The best place to watch is any place that has a clear view of the southeastern sky and is away from city lights. I'm not much of a photo guy, but a friend sent me this information about photographing the Leonids:
The Leonids can be photographed using the traditional method of taking "star-trails", but the results are often disappointing, as the Leonids are rather faint compared to other meteor showers.
Using a tracking telescope arrangement can provide good results, but again, the Leonids are faint and hard to capture on film.
Using a bright aperture (f2.8 or brighter) and a faster film (iso 400+) will improve your results. If you use color film, be sure to use one with low reciprocity failure, otherwise the colors will be strange.
Do get away from light-pollution as much as possible, as well as aircraft flight paths, and also the headlights from the cars of fellow star-watchers. The Leonids are faint on film, so any stray light can wash-out the Leonids on your film.
The length of the exposure does NOT effect the ability of the film to capture the Leonids, other than to perhaps capture more of them on one frame of film. Using longer exposures such as those typically used to capture star-trails can work, but beware of excessive stray light that can wash-out the faint Leonids on longer exposures.
Glover Park:
Will I be able to see this shower within the city? I have a non-lighted park near my house that is pretty well sheltered from direct light, but is the ambient light of the city going to be too much?
Dr. Glenn Peterson: As long as your view of the southeastern sky is clear, the dark park will probably give up a pretty good view. Take a look tonight, if you can see a good representation of stars, then you will probably be able to see a good collection of meteors. Use the stars as your guide.
Maryland:
I will get home from work around 1:30am Sunday. Will I be able to see anything around that time, or will I have to wait until just before dawn? I am trying to decide if it is worth only getting 3 hours of sleep on a Sunday.
Dr. Glenn Peterson: What?? Who let this guy in here?? Of course its worth only getting 3 hours of sleep!! :) Seriously, the Leonids only exhibit this level of activity every 33 years. And even then, there is no guarantee that every 33 years, the activity will be this high. In 1966, the activity peaked at 150,000 meteors per hour; this year it MAY peak over Australia at 5000 to 15000 per hour. Over the US it may be a couple thousand per hour. This is the best chance in our lifetimes to see something like this. There is some thought that next year will be similar to this, but I personally have my doubts about those predictions until I see what happens this year. So go out and enjoy! If your boss complains about you being groggy, tell him I said it was ok.
Alexandria, Va.:
What can be done to keep satellites safe from space particles? Have any been hurt before by meteor showers?
Dr. Glenn Peterson: Yes they have. Solar-A (a Japanese spacecraft) had its lightshield penetrated by a meteor which hurt its science mission. The worst has been Olympus-1, which was a European telecommunications satellite. No real damage was done to the spacecraft, but it lost its lock on the Sun. The vehicle was commanded to relocate the Sun, but it used so much fuel that the mission was effectively over. For the Leonids, most satellite operators are going to a higher state of awareness in monitoring their spacecraft. They are aware of the Leonids and what threat that is posed, so they are cautious and alert, but there isn't a whole lot that can be done to reduce the threat once a satellite is on-orbit. Some operators are placing their solar panels so that the panels are edge-on to the approaching meteors, but that is about the extent of what they can do.
Washington, D.C.:
How far away from the city lights do I have to be to see the Leonids? Obviously D.C. is not as bright as NYC or Vegas, and I was planning to watch from a rooftop in nearby Arlington -- but I'm concerned that it will still be too bright. What do you think my chances are of catching a glimpse without trekking out to the country?
Dr. Glenn Peterson: Use the stars as your guide. The best way to gauge whether you can see the Leonids or not is to take a look tonight at the stars in the sky. If you can see a good number of stars, not just the bright ones, but the faint ones as well, then you should be able to see a good level of Leonid activity.
Reston, Va.:
For how many years has this astronimical event been occuring in the night sky of mid-November?
Dr. Glenn Peterson: The Leonids have been observed for over a thousand years. Big nightime events were especially watched by astronomers in ancient times and were thought to be omens. The earliest known Leonid observation occurred in 902 AD. However, due to orbital perturbations, the Leonids could not have been seen before that, and unfortunately these same perturbations are going to carry the stream away from Earth in the near future. After 2099, there will be no more Leonids!! So look now, cause they will not be there forever.
Springfield, Va.:
Will the shower also be seen over Europe, and would the intensity there be an indication of what we're in store for (that is, some extra motivation to jump out of bed at 4 a.m.)?
Dr. Glenn Peterson: The Leonid shower actually lasts for about 2 weeks total. However, away from the peak, the activity is usually not very large. Europe won't get a big show this year and it will be hard to predict what the activity over the US will be by depending upon the European observations. Europe may see meteor rates of 100 per hour or so, but that's not going to tell us in the US whether we will see really big numbers or not. So get out of bed, lazyhead!
Alexandria, Va.:
Do you know if it would it be possible to video tape the meteor shower? I have a fairly high end professional camera if this matters.
Dr. Glenn Peterson: I don't know how successful that would be. If you have good equipment, I'd give it a try. You could attempt it with a few meteors at first and make a judgement as to whether it's worth pursuing. The Washington Post might be interested in getting good pictures.:)
Torrance, Calif.:
Hi Dr. Peterson,
Does the peak time of 5 a.m. EST mean the peak on the west coast will be 2 a.m. PST? or is the Earth rotating into the trail?
Dr. Glenn Peterson: You got it right. Around 2 am PST will be the time for those of us on the west coast. However, there is an element of uncertainty associated with meteor predictions. I plan on going out to the high desert after midnight (PST) and watching until dawn. The Earth is rotating into the trail and that's why all the predictions are for AFTER midnight. Due to the Earth's rotation, we can't see the meteors before midnight.
Washington, D.C.:
What about earlier in the night? I understand why before midnight might not be a good time, but is there a chance that there will be some meteors before midnight and, generally, should we look closer to the Eastern horizon?
Thanks
Dr. Glenn Peterson: Due to the Earth's rotation, we can't see the Leonids before midnight. The Leonids are approaching the Earth at almost right angles (90 degrees) to the Earth-Sun line (i.e. dawn). So we see them best after midnight as the Earth rotates into the stream. Before midnight, we literally are on the wrong side of the world.
Washington, D.C.:
What about the ISS? Are they taking any precautions?
Dr. Glenn Peterson: The ISS is taking precautions, but my last understanding was that they were allowing the astronauts to stay on board. The onboard crew will be alert to the situation and prepared, but they are not abandoning station. In 1999, NASA decided not to fly the Shuttle during the Leonids, and this year, there are no planned Shuttle missions.
Annapolis, Md.:
As a side question, I've always wondered how the solar systems travel through space. If one were to place a grid in space would the solar system move consistenly across a single plane, or would it look more like a roller coaster dipping up and down, but always maintained forward momentum?
Dr. Glenn Peterson: It would actually dip up and down, but always maintaining the forward momentum. If you think of a satellite orbitting the Earth, then other planetary bodies like the Moon and Sun (and the other planets) will perturb the satellite's orbit and cause slight fluctuations. The same applies for the Sun travelling around the center of the Milky Way. Other stars, and some exotic Einsteinian relativistic forces, will cause perturbations in the Sun's motion.
| |
© Copyright 2002 The Washington Post Company | 
