LEONIDS 2000
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
November 16, 2000
On Friday, Nov. 17, and Saturday, Nov. 18, Earth will travel through the tail of dust from Comet Tempel-Tuttle. As the dust particles -- tiny meteoroids -- burn up in Earth's atmosphere, they give the appearance of "shooting stars," called meteors. This display, known as the Leonid meteor shower, may be most visible over North America's East Coast. That's because the constellation Leo, where the meteors seem to come from, will be in a dark part of the sky high above the eastern horizon.
The Leonids, however, may produce only a minor shower this year -- about one streak per minute. The Moon's brightness can also reduce the visibility of the meteors.
"The third-quarter Moon will be in Leo, making the sky bright and the Leonids a bit difficult to see," said comet scientist Dr. Don Yeomans of the Jet Propulsion Laboratory, Pasadena, Calif.
The best way to see the Leonids shower is to block the Moon's brightness with a hand or tree. On North America's West Coast this week, look in the general direction of the Moon on Friday night from 11:30 p.m. until after midnight. Some meteor activity may be evident the night before at the same time. From the East Coast, look in the general direction of the Moon at about 2:50 a.m. on Saturday, when the showers should be strongest.
Every 33 years, Comet Tempel-Tuttle travels through the inner solar system. The comet, which is basically a ball of dust and ice, last passed close to the Sun and was visible from Earth in March 1998. Near the Sun, the comet's ices begin to vaporize and the embedded dust particles fall away and trail the comet in its orbit. Every year, Earth passes through the trail of debris left behind by the comet, and the comet dust particles plunge into Earth's atmosphere at some 71 kilometers (44 miles) per second -- fast enough to travel from Los Angeles to New York in about one minute.
ESA
November 15, 2000
One of the most exciting things about meteor showers is their sheer unpredictability. Just when astronomers think they know all about a particular shower, something happens to spring a surprise. One of the least predictable of the annual meteor showers is the Leonids, which appears each year around 16-18 November.
Although this year's shower is not expected to reach storm proportions, ESA scientists are continuing their efforts to learn more about the cosmic debris that is incinerated as it enters Earth's upper atmosphere.
Find out more about the Leonids.
ROYAL OBSERVATORY GREENWICH
14 November 2000
For observers in the UK and Europe, the best chance of seeing meteors will be at 03:44 on the morning of 18 November, as the Earth passes close to a stream of debris released by comet Temple-Tuttle 260 years ago. At this time it may be possible to see as many as 100 meteors an hour. This is ten times the background rate that can be seen on any other night of the year.
The Earthıs orbit passes close to the comet Temple Tuttleıs orbit each year in November and during this time the Earth collides with particles of cometary debris which follow the cometıs orbit.
Meteors can be seen on any clear night of the year and most are caused by particles no bigger than grains of sand, which collide with the Earthıs atmosphere at up to 70km per second (157,000 mph) and burn up. Fireballs are caused by meteors a few centimetres in diameter and can leave tails that persist for several minutes.
Dr Robert Massey will be taking students from the Royal Observatoryıs GCSE astronomy class out to a dark site in the Kent countryside on the night of 17 November to observe the meteors and measure the level of activity. The observers will also take the opportunity to look at the Moon, stars and planets away from the lights of London.
AstroAlert
Novemver 13, 2000
At least this year we are rather sure as to when any enhanced activity could occur rather than spending the entire morning waiting for something to happen. Our first opportunity occurs on Friday morning November 17 when the earth passes close to the comet dust left behind in 1965 and 1932. This will occur near 8:00 Universal Time (UT) which corresponds to 3:00 AM Eastern Standard Time and midnight Pacific Standard time. Those in the eastern half of North America will be favored to see the most meteor activity as the radiant will lie high in the sky at this time. Those situated along the west coast will have a low radiant altitude which will reduce the activity significantly.
If your skies are clear then plan to start observing at least one hour before the time of maximum activity. Face toward a portion of the sky so that the moon is out of your field of view. Also remember to look up high enough so that none of your view is wasted on the ground. This corresponds to at least an altitude of 45 degrees. Scientific data can be obtained by simply counting the number of Leonids and non Leonids seen. 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. Of course this all changes if you change the direction in which you are facing. 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 estimates should be near +5.0. Meteor reports can be sent to me at: lunro.imo.ysa@home.com and to Sky & Telsecope.
On Saturday morning November 18 there exists two more opportunities for enhanced Leonid rates. The first occurs at 3:45 UT which is too early for North American observers. The Leonid radiant will be below the horizon at this time in North American but well placed for Europe and Africa. This enhancement may occur as the earth passes through the outer fringes of the dust trail left behind in 1733.
The last opportunity occurs some four hours later near 07:50 UT. Eastern North America and South America will be the favored locations for this enhancement. This corresponds to 2:50 AM EST and 11:50 PM (11/17) PST. At this time the earth will pass the outer edges of the dust trail created in 1866. Once again rates are not expected to be particularly impressive, especially when compared to the storm rates that were witnessed last year.
For more information on observing meteors visit the Sky & Telescope Web pages.
A weekly preview of current meteor activity is also published each
Thursday at:
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
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NASA Ames Research Center, Moffett Field, CA
Nov. 13, 2000
The scientists - all members of the NASA and U.S. Air Force-sponsored Leonid Multi-Instrument Aircraft Campaign - discussed their results in a series of astrobiology-related papers in the peer-reviewed journal. While their findings covered a range of areas, the key results reported have implications for the existence and survival of life's precursors in comet materials that reach Earth.
"Last year's Leonid meteor storm yielded rich research results for NASA astrobiologists," said Dr. Peter Jenniskens, a NASA astronomer based at Ames Research Center and principal investigator for the airborne research mission. "Findings to date indicate that the chemical precursors to life -- found in comet dust -- may well have survived a plunge into early Earth's atmosphere."
Jenniskens and his international cadre of researchers think that much of the organic matter in comet dust somehow survived the rapid heating of Earth's atmospheric entry. "Organic molecules in the meteoroid didn't seem to burn up in the atmosphere," he explained. They may have cooled rapidly before breaking apart, he concluded.
Another manner in which organic matter can somehow survive the fiery plunge into Earth's atmosphere was discovered by a team from the Aerospace Corporation, Los Angeles, who detected the fingerprint of complex organic matter, identical to space-borne cometary dust, in the path of a bright Leonid fireball. This "fingerprint" is still under investigation to ensure that trace-air compounds are not contributing to the detection.
Another finding with potentially important implications for astrobiology is that meteors are not as hot as researchers had previously believed. "We discovered that most of the visible light of meteors comes from a warm wake just behind the meteor, not from the hot meteoroid's head," said Jenniskens. This warm wake has just the right temperature for the creation of life's chemical precursors, he said.
Utah State University researchers found that, during the meteors' demise in the atmosphere, their rapid spinning caused small fragments to be ejected in all directions, quite far from the meteoroid's head. This is an important finding for astrobiology, because it means that meteors may be able to chemically alter large amounts of atmosphere.
This year, the 2000 Leonid meteor shower is expected to peak twice -- once on Thursday night November 16 and again on Friday night November 17. Although not as strong as last year's storm, meteors will be visible across the continental United States, with the East Coast predicted to provide the best meteor viewing. Each night, optimal East Coast viewing will be at approximately 2:50 a.m. (EST). West Coast observers can glimpse the showers beginning after 11:00 p.m. (PST), and peaking between midnight and 1:30 a.m. Astronomers recommend that, because this year's showers take place during a last-quarter moon, optimal observing conditions demand a wide field of view, with the moon behind trees or buildings.
An observing tool called the "Leonid MAC flux estimator" is available for the general public. It predicts how much meteor activity is expected at a particular U.S. observing location. Further images from 1999's meteor storm, information about "Earth, Moon and Planets" and other Leonids information can be found at: amesnews.arc.nasa.gov.
Astrobiology is the study of the origin, evolution, dissemination and future of life in the universe. NASA's Ames Research Center, in the heart of California's Silicon Valley, is the Center of Excellence for NASA's astrobiology research. It is also the location of the central offices of the NASA Astrobiology Institute, an international research partnership - among NASA and non-NASA agencies and institutions - to further astrobiology research.
Marshall Space Flight Center
Huntsville, AL
November 8, 2000
Part of the monitoring activities will include the launch of a weather balloon carrying video and audio equipment which will allow scientists and the public to actually hear what a meteor sounds like as it crashes into Earth's atmosphere.
The public, particularly along the East Coast, also will be able to look up and, depending on weather conditions, see perhaps 700 or more shooting stars per hour.
Three peak times for the showers are forecast for the East Coast -- Nov. 17 at about 3 a.m. EST and again at 11 p.m. EST, and Nov. 18 at about 3 a.m. EST -- according to Bill Cooke, senior computer scientist at the Marshall Center.
A Leonids 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. As Earth travels through the comet dust, the debris burns up in the Earth's atmosphere resulting in shooting stars or meteors. Some of these dust streams actually broke away from the comet long ago. Meteors visible this year date to 1932, 1866 and 1733.
"This year, the Moon will be in the constellation Leo -- practically on top of the Leonids radiant," said Mitzi Adams, a Marshall Center astronomer. "Moonlight will make fainter meteors hard to spot, but if there's a strong outburst, stargazers could see plenty of Leonids in spite of the bright Moon."
Because this year's peak meteor activity is not projected to reach storm level -- at least 1,000 meteors per hour -- Marshall scientists will use the opportunity to test their accuracy at predicting Leonids intensity.
In 1999, a true "storm" occurred when up to 3,700 meteors per hour were recorded over Israel.
"We can predict within minutes the time the meteors will peak," said Marshall Space Environment Team researcher Dr. Rob Suggs. "What we have trouble with is predicting the intensity."
If the intensity of a Leonids shower can be accurately predicted, scientists will know which way orbiting satellites should be turned to keep them operating smoothly during meteor activity.
"Satellites are an integral part of our lives now, so anything that affects these satellites directly affects our lives," Suggs said, citing as examples communications and television satellites.
To help protect these satellites from the fast-travelling meteors, Marshall scientists will analyze information from the various monitoring teams and pass it along to satellite operators.
Although a typical meteor is smaller than a grain of sand, it travels 12 miles (20 kilometers) per second. Leonids are the fastest of all meteors -- traveling at about 44 miles (71 kilometers) per second. At that speed, a Leonids meteor could travel from New York to Los Angeles in about one minute.
Heavy Leonids meteor storms are predicted for 2001 and 2002.
"We are getting predictions from models for next year in excess of 10,000 meteors per hour over East Asia and Mongolia," Suggs said. "In 2002, predictions are in excess of 25,000 meteors per hour over the East Coast of the United States."
The Marshall Center is NASA's lead center for monitoring and forecasting meteor showers. Huntsville scientists will begin monitoring Nov. 16, using two image-intensified camera systems and recording the meteors onto videotape.
"This year we also have a forward-scatter radar that will allow us to 'hear' the meteors," Suggs said, explaining that the noises are caused by the meteors interacting with ionized gas or plasma in the Earth's atmosphere.
Besides monitoring the Leonids from Huntsville, Marshall scientists also will coordinate monitoring teams at the following locations:
In addition to the observing teams, Marshall scientists, weather permitting, will launch a 10-foot (3-meter) diameter weather balloon from Marshall's Atmospheric Research Facility at 12:30 a.m. CST on Nov. 18. The balloon will ascend approximately 20 miles (32 kilometers), carrying a sensitive camera for capturing high-resolution television pictures of the meteors. During the three-to- four-hour flight, the television pictures can be viewed online at the Marshall Center's Science Directorate Web site at: Leonids, Live!
The balloon also will carry a very low frequency radio receiver that will allow visitors to the Web site to hear the "whistlers" and other bizarre noises that meteors might make as they enter the Earth's atmosphere. On-board transmitters will allow local amateur radio operators, or "hams," to track and retrieve the balloon.
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