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The Quadrantids are a January meteor shower. The zenithal hourly rate of this shower can be as high as two other reliably rich meteor showers, the Perseids in August and the Geminids in December. Yet Quadrantid meteors aren’t seen as often as meteors in these other two showers, because the peak intensity is exceedingly sharp, sometimes lasting only hours.
The meteor rates exceed one-half of their highest value for only about 8 hours. This means that the stream of particles that produces this shower is narrow – and apparently deriving from and within the last 500 years from some orbiting body. The parent body of the Quadrantids was tentatively identified in 2003 by Peter Jenniskens as the minor planet 2003 EH1, which in turn may be related to the comet C/1490 Y1 that was observed by Chinese, Japanese and Korean astronomers some 500 years ago.
The radiant point of this shower is an area inside the constellation Boxtes, not far from the Big Dipper. It lies between the end of the handle of the Big Dipper and the quadrilateral of stars marking the head of the constellation Draco. This meteor shower is best seen in the northern hemisphere, but you can see Quadrantids down to -51 degrees latitude.
The name comes from Quadrans Muralis, an obsolete constellation that is now part of Boxtes. The French astronomer Jerome Lalande created this constellation in 1795. In early January 1825, Antonio Brucalassi in Italy reported that “the atmosphere was traversed by a multitude of the luminous bodies known by the name of falling stars.” They appeared to radiate from Quadrans Muralis. In 1839, Adolphe Quetelet of Brussels Observatory in Belgium and Edward C. Herrick in Connecticut independently made the suggestion that the Quadrantids are an annual shower.
In 1922, the International Astronomical Union devised a list 88 modern constellations. The list was agreed upon by the International Astronomical Union at its inaugural General Assembly held in Rome in May 1922. It didn’t include a constellation Quadrans Muralis. The IAU officially adopted this list in 1930, but this meteor shower still retains the name Quadrantids, for the original and now obsolete constellation Quadrans Muralis.
Related Sites for Quadrantids
1913 Great Meteor Procession
The 1913 Great Meteor Procession occurred on February 9, 1913. It was a unique meteoric phenomenon reported from locations across Canada, the northeastern United States, and Bermuda, and from many ships at sea, including eight off Brazil, giving a total recorded ground track of over 7,000 miles. The meteors were particularly unusual in that there was no apparent radiant, that is to say, no point in the sky from which the meteors appeared to originate. The observations were analysed in detail, later the same year, by the astronomer Clarence Chant, leading him to conclude that as all accounts were positioned along a great circle arc, the source had been a small, short-lived natural satellite of the Earth.
A huge meteor appeared travelling from northwest by west to southeast, which, as it approached, was seen to be in two parts and looked like two bars of flaming material, one following the other. They were throwing out a constant stream of sparks and after they had passed they shot out balls of fire straight ahead that travelled more rapidly than the main bodies. They seemed to pass over slowly and were in sight about five minutes. Immediately after their disappearance in the southeast a ball of clear fire, that looked like a big star, passed across the sky in their wake. This ball didn’t have a tail or show sparks of any kind. Instead of being yellow like the meteors, it was clear like a star.
Subsequent observers also noted a large, white, tail-less body bringing up the rear, but the various bodies making up the meteor procession continued to disintegrate and to travel at different rates throughout their course, so that by the time observations were made in Bermuda, the leading bodies were described as “like large arc lights in appearance, slightly violet in colour”, followed closely by yellow and red fragments.
Research carried out in the 1950s by Alexander D. Mebane uncovered a handful of reports from newspaper archives in the northern United States. At Escanaba, Michigan, the Press stated the “end of the world was apprehended by many” as numerous meteors travelled across the northern horizon. In Batavia, New York, a few observers saw the meteors and many people heard a thundering noise, while other reports were made in Nunda-Dansville, New York and Osceola, Pennsylvania.
One curious feature of the reports, highlighted by Mebane, was that several appeared to indicate a 2nd meteor procession on the same course around 5 hours later, although the Earth’s rotation meant that there was no obvious mechanism to explain this. One observer, an A. W. Brown from Thamesville, Ontario, reported seeing both the initial meteor procession and a 2nd one on the same course at 02:20 the next morning. Chant’s original report also referred to a series of three groups of “dark objects” which passed, on the same course as the previous meteors, from west to east over Toronto on the afternoon of February 10, which he suggested were “something of a meteoric nature”.
The 1st detailed study of the reports was produced by the Canadian astronomer Clarence Chant, who wrote about the meteors in vol. 7 of the Journal of the Royal Astronomical Society of Canada. The orbit was later discussed by Pickering and G. J. Burns, who concluded that it was essentially satellitic. Although this explanation was later attacked by Charles Wylie, who attempted to prove that the shower had a radiant, further studies by Lincoln LaPaz and John O’Keefe showed that the meteors had most likely represented a body, or group of bodies, which had been temporarily captured into orbit about the Earth before disintegrating.
O’Keefe later suggested that the meteors, which he referred to as the “Cyrillids”, could have in fact represented the last remnant of a circumterrestrial ring, formed from the ejecta of a postulated lunar volcano. This theory was a development of O’Keefe’s unusual hypothesis on the origin of tektites.
Related Sites for 1913 Great Meteor Procession
- Remembering the Great Meteor Procession of 1860 read 1913 Great Meteor Procession
- 150-year-old meteor mystery solved – NBC News.com read 1913 Great Meteor Procession
- rosenthal | eBay – Electronics, Cars, Fashion, Collectibles … read 1913 Great Meteor Procession
- Lights in the Sky. – Motygido read 1913 Great Meteor Procession
Petrus Matheus Marie Jenniskens (born 2 August 1962, Horst) is a Dutch and US astronomer and a senior research scientist at the Carl Sagan Center of the SETI Institute and at NASA Ames Research Center. He is an expert on meteor showers. Jenniskens is the author of the 790 page book “Meteor Showers and their Parent Comets” published by Cambridge University Press in 2006. Jenniskens is president of Commission 22 of the International Astronomical Union (2012-2015) and was chair of the Working Group on Meteor Shower Nomenclature (2006–2012) after it was 1st established. Discovered at Ondřejov Observatory by Petr Pravec, asteroid “42981 Jenniskens” is named in his honor.
In 2008, Jenniskens together with Muawia Shaddad, lead a team from the University of Khartoum in Sudan that recovered fragments of asteroid 2008 TC3 in the Nubian Desert, marking the 1st time meteorite fragments had been found from an object that was previously tracked in outer space before hitting Earth.
Jenniskens is the principal investigator of NASA’s Leonid Multi-Instrument Aircraft Campaign, a series of four airborne missions that fielded modern instrumental techniques to study the 1998 – 2002 Leonids meteor storms. These missions helped develop meteor storm prediction models, detected the signature of organic matter in the wake of meteors as a potential precursor to origin-of-life chemistry, and discovered many new aspects of meteor radiation.
More recent meteor shower missions include the Aurigid Multi-Instrument Aircraft Campaign, which studied a rare September 1, 2007, outburst of Aurigids from long-period comet C/1911 N1 (Kiess), and the Quadrantid Multi-Instrument Aircraft Campaign (Quadrantid MAC), which studied the January 3, 2008, Quadrantids.
Jenniskens identified several important mechanisms of how our meteor showers originate. Since 2003, Jenniskens identified the Quadrantids parent body 2003 EH1, and several others, as new examples of how fragmenting comets are the dominant source of meteor showers. These objects are now recognized as the main source of our zodiacal dust cloud. Before that, he predicted and observed the 1995 Alpha Monocerotids meteor outburst, proving that “stars fell like rain at midnight” because the dust trails of long-period comets wander on occasion in Earth’s path.
His research also includes artificial meteors. Jenniskens is the principal investigator of NASA’s Genesis and Stardust Entry Observing Campaigns to study the fiery return from interplanetary space of the Genesis and Stardust (Jan. 2006) sample return capsules. These airborne missions studied what physical conditions the protective heat shield endured during the reentry before being recovered.
More recently, Jenniskens led a mission to study the destructive entry of ESA’s Automated Transfer Vehicle “Jules Verne” on 29 September 2008 and the beautiful reentry of JAXA’s Hayabusa probe over Australia on 13 June 2010. An overview of ongoing missions can be found at:.
The next biggest impact over land occurred in California’s gold country on April 22, 2012. One of the fragments landed at Sutter’s Mill, the very site where gold was 1st discovered in 1848 that led to the California Gold Rush. Jenniskens found one of three fragments of this CM chondrite on April 24, before rains hit the area. The rapid recovery was made possible because Doppler weather radar detected the falling meteorites. A consortium study led by Jenniskens traced these meteorites back to a source region in the asteroid belt: a family of asteroids that move at low inclination and are close to the 3:1 mean-motion resonance with Jupiter.These were the 1st CM chondrites to be recovered from near the surface of the original parent body before it broke up, creating the asteroid family.
In earlier collaborations, he discovered that an unusual viscous form of liquid water can be a common form of amorphous ice in comets and icy satellites and he created the 1st broad detection-limited survey of Diffuse Interstellar Bands in his PhD thesis work with Xavier Dxsert.
Related Sites for Peter Jenniskens
- 2008 Quadrantids – The Quadrantid Multi-Instrument Aircraft Campaign read Peter Jenniskens
- Meteor Showers and their Parent Comets – 9780521853491 – Cambridge … read Peter Jenniskens
- Astronomer finds meteorite pieces in Gold Country – SFGate read Peter Jenniskens
- Photos: Fireball Drops Meteorites On Calif. | Meteorites | Space.com read Peter Jenniskens
The Orionid meteor shower, usually shortened to the Orionids, is the most prolific meteor shower associated with Halley’s Comet. The Orionids are so-called because the point they appear to come from, called the radiant, lies in the constellation Orion, but they can be seen over a large area of the sky. Orionids are an annual meteor shower which last approximately one week in late-October. In some years, meteors may occur at rates of 50-70 per hour.
Meteor showers 1st designated “shooting stars” were connected to comets in the 1800s. E.C. Herrick made an observation in 1839 and 1840 about the activity present in the October night skies. However A.S. Herschel produced the 1st documented record which produced accurate forecasts for the next meteor shower. The Orionid meteor shower is produced by the well-known Halley’s Comet, which was named after the astronomer Edmund Halley and last passed through the inner solar system in 1986 on its 75-to-76-year orbit. When the comet passes through the solar system, the sun sublimates some of the ice which allows rock particles to break away from the comet. These particles continue on the comet’s trajectory and appear as meteors or “falling stars” when they pass through Earth’s upper atmosphere. Halley’s comet is also responsible for creating the Eta Aquariids which occur annually in May.
This meteor shower may give double peaks as well as plateaus, and time periods of flat maxima lasting several days.
An Orionid near the center.
A fish-eye view.
Two Orionids and the Milky Way.
A multicolored Orionid.
An Orionid to the left.
The brightest meteor, a fireball, leaves a persistent smoky trail drifting in high-altitude winds, which is seen on the right side of the image.
Related Sites for Orionids
The object was undetected before its atmospheric entry and its explosion created considerable confusion among local residents. About 1,500 people were injured seriously enough to seek medical treatment. All of the injuries were due to indirect effects rather than the meteor itself, mainly from broken glass from windows that were blown in when the shock wave arrived, minutes after the superbolide’s flash. Some 7,200 buildings in six cities across the region were damaged by the explosion’s shock wave, and authorities scrambled to help repair the structures in sub-zero temperatures.
With an estimated initial mass of about 10,000 tonnes, and measuring between 17 and 20 metres in size, it is the largest known natural object to have entered Earth’s atmosphere since the 1908 Tunguska event that destroyed a wide, remote, forested area of Siberia. The Chelyabinsk meteor is also the only meteor confirmed to have resulted in a large number of injuries. The predicted close approach of a 2nd asteroid, the roughly 30-metre 2012 DA14 occurred about 16 hours later; detailed analysis of the two objects later determined that they were unrelated to each other.
Local residents witnessed extremely bright burning objects in the sky in Chelyabinsk, Sverdlovsk, Tyumen, and Orenburg Oblasts, the Republic of Bashkortostan, and in neighbouring regions in Kazakhstan, when an asteroid entered the Earth’s atmosphere over Russia. Amateur videos showed a fireball streaking across the sky and a loud boom several minutes afterwards. Eyewitnesses also felt intense heat from the fireball.
The event began at 09:20 Yekaterinburg time, several minutes after sunrise in Chelyabinsk, and minutes before sunrise in Yekaterinburg. According to eyewitnesses the bolide was brighter than the sun, and were not believed until this was confirmed as a fact by American Scientists at NASA. An image of the object was also taken shortly after it entered the atmosphere by the weather satellite Meteosat 9. Witnesses in Chelyabinsk said that the air of the city smelled like gunpowder.
The visible phenomenon due to the passage of an asteroid or meteoroid through the atmosphere is called a meteor. If the object reaches the ground, then it is called a meteorite. During the Chelyabinsk meteor‘s traversal, there was a bright object trailing smoke, then an air burst that caused a powerful shock wave, the cause of the damage to thousands of buildings in Chelyabinsk and its neighbouring towns. The fragments entered dark flight (without the emission of light) and created a strewn field of numerous meteorites on the snow-covered ground (officially named Chelyabinsk meteorites).
According to the Russian Federal Space Agency, preliminary estimates indicated the object was an asteroid moving at about 30 km/s in a “low trajectory” when it entered Earth’s atmosphere. According to the Russian Academy of Sciences, the meteor then pushed through the atmosphere at a velocity of 15 km/s. The radiant appears from video recordings to have been above and to the left of the rising Sun.
The last time a similar phenomenon was observed in the Chelyabinsk region was the Kunashak meteor shower of 1949, after which scientists recovered about 20 meteorites weighing over 200 kg in total. The Chelyabinsk meteor is thought to be the biggest natural space object to enter Earth’s atmosphere since the 1908 Tunguska event, and the only one confirmed to have resulted in a large number of injuries,[Note 1] although a small number of panic-related injuries occurred during the Great Madrid Meteor Event of 10 February 1896.
In the days immediately after the initial visual meteor sighting, officials in the neighbouring country of Kazakhstan said they were looking for two possible unidentified objects that may have impacted in Aktobe Province, adjacent to the affected Russian regions. To date, no further announcements have been made.
The meteor’s unpredicted arrival and air burst resulted in considerable injuries. Russian authorities stated that 1,491 people, including 311 children, sought medical attention in Chelyabinsk Oblast within the 1st few days. Health officials said 112 people had been hospitalised, with two in serious condition. A 52-year-old woman with a broken spine was flown to Moscow for treatment. Most people were hurt by shattered, falling or blown-in glass.
A fourth-grade teacher in Chelyabinsk, Yulia Karbysheva, saved 44 children from potentially life threatening imploding window glass cuts. Despite not knowing the origin of the intense flash of light, Ms. Karbysheva thought it prudent to take precautionary measures by ordering her students to stay away from the room’s windows and to perform a duck and cover maneuver. Ms. Karbysheva, who herself didn’t duck and cover but remained standing, was seriously lacerated when the air blast arrived and window glass severed a tendon in one of her arms; however, not one of her students, who she ordered to hide under their desks, suffered a cut.
After the air blast, car alarms went off and mobile phone networks were overloaded with calls. Office buildings in Chelyabinsk were evacuated. Classes for all Chelyabinsk schools were cancelled, mainly due to broken windows. At least 20 children were injured when the windows of a school and kindergarten were blown in at 09:22. Following the event, government officials in Chelyabinsk asked parents to take their children home from schools.
By 5 March 2013 the number of damaged buildings was tallied at over 7,200, which included some 6,040 apartment blocks, 293 medical facilities, 718 schools and universities, 100 cultural organizations, and 43 sport facilities, of which only about one and a half percent had not yet been repaired. The oblast’s governor estimated the damage to buildings at more than 1 billion rubles. Chelyabinsk authorities said that broken windows of apartment homes, but not the glazing of enclosed balconies, would be replaced at the state’s expense. One of the buildings damaged in the blast was the Traktor Sport Palace, home arena of Traktor Chelyabinsk of the Kontinental Hockey League (KHL). The arena was closed for inspection, affecting various scheduled events, and possibly the postseason of the KHL.
On the day of the impact, Bloomberg News reported that the United Nations Office for Outer Space Affairs had suggested the investigation of creating an “Action Team on Near-Earth Objects”, a proposed global asteroid warning network system, in face of 2012 DA14′s approach. As a result of the impact, two scientists in California have proposed directed-energy weapon technology development as a possible means to protect Earth from asteroids.
The Russian government put out a brief statement within an hour of the event, but the event was 1st covered in the US by hockey blog Russian Machine Never Breaks. Discussion on social media sites started almost immediately after the event, and heavy coverage by the international media had begun by the time the Associated Press put out a brief report with the Russian government’s confirmation less than two hours afterwards. Less than 15 hours after the meteor impact, videos of the meteor and its aftermath had been viewed millions of times.
The number of injuries caused by the asteroid led the Internet-search giant Google to remove a Google Doodle from their website, created for the predicted pending arrival of another asteroid, 2012 DA14. New York City planetarium director Neil deGrasse Tyson stated the Chelyabinsk meteor was unpredicted because no attempt had been made to find and catalogue every 15-metre near-Earth object. In television media interviews shortly afterwards Tyson also noted the disturbing closeness of the two completely unrelated events.
On 27 March 2013 a broadcast episode of NOVA titled “Meteor Strike” documented the Chelyabinsk meteor, including the large amounts of meteoritic science revealed by the numerous videos of the airburst posted online by ordinary citizens. The NOVA program called the video documentation and the related scientific discoveries of the airburst “unprecedented”. The documentary also discussed the much greater tragedy “that could have been” had the asteroid entered the Earth’s atmosphere more steeply.
Multiple videos of the Chelyabinsk superbolide, particularly from dashboard cameras and traffic cameras, helped to establish the meteor’s provenance as an Apollo asteroid. Sophisticated analysis techniques included the subsequent superposition of nighttime starfield views over recorded daytime images, as well as the plotting of the daytime shadow vectors shown in several online videos.
The radiant of the impacting asteroid was located in the constellation Pegasus in the Northern hemisphere. The radiant was close to the Eastern horizon where the Sun was starting to rise.
The asteroid belonged to the Apollo group of near-Earth asteroids, and was roughly 40 days past perihelion and had aphelion (furthest distance from the Sun) in the asteroid belt. Several groups independently derived very similar orbits for the object. The Apollo asteroid 2011 EO40 is the most likely candidate for the role of the parent body of the Chelyabinsk superbolide.
In the aftermath of the air burst of the body, a large number of small meteorites fell on areas west of Chelyabinsk, generally at terminal velocity, about the speed of a piece of gravel dropped from a skyscraper. Local residents and schoolchildren located and picked up some of the meteorites, many located in snowdrifts, by following a visible hole that had been left in the outer surface of the snow. Speculators have been active in the informal market that has rapidly emerged for meteorite fragments.
In 2014 Winter Olympics in Sochi 7 gold medals that can be earned during eighth day medal events will feature fragments of the Chelyabinsk meteorite. Medal events planned at that day are: the men’s 1,500-meter speedskating, the women’s 1,000 and men’s 1,500 short track, the women’s cross-country skiing relay, the men’s K-125 ski jump, the women’s super giant slalom and the men’s skeleton.
Related Sites for Chelyabinsk meteor
- Meteor Blast Over Russia Feb. 15 | Complete Coverage | Space.com read Chelyabinsk meteor
- Scientist: Chelyabinsk meteor scared the world, NASA’s priorities … read Chelyabinsk meteor
- Chelyabinsk meteor: Astronomers trace it back to a potential … read Chelyabinsk meteor
- NASA Tracks Chelyabinsk Meteor Maybe More to Come read Chelyabinsk meteor
The radiant or apparent radiant of a meteor shower is the point in the sky, from which meteors appear to originate. The Perseids, for example, are meteors which appear to come from a point within the constellation of Perseus.
An observer might see such a meteor anywhere in the sky but the direction of motion, when traced back, will point to the radiant. A meteor that does not point back to the known radiant for a given shower is known as a sporadic and isn’t considered part of that shower.
Many showers have a radiant point that changes position during the interval when it appears. For example, the radiant point for the Delta Aurigids drifts by more than a degree per night.
Meteor showers are mostly caused by the trails of dust and debris left in the wake of a comet. This dust continues to move along the comet’s wake, and when the Earth moves through such debris, a meteor shower results. Because all of the debris is moving in roughly the same direction, the meteors which strike the atmosphere all “point” back to the direction of the comet’s path.
As an exception, the Geminids are a shower caused by the object 3200 Phaethon, which is thought to be a Palladian asteroid.
The radiant is an important factor in observation. If the radiant point is at or below the horizon, then few if any meteors will be observed. This is because the atmosphere shields the Earth from most of the debris, and only those meteors which happen to be travelling exactly tangential to the Earth’s surface will be viewable.
Related Sites for Radiant
- Radiant Recovery
List of meteor showers
This list of meteor streams and peak activity times is based on data from the International Meteor Organization while most of the parent body associations are from Gary W. Kronk book, Meteor Showers’: A Description Catalog, Enslow Publishers, New Jersey, ISBN 0-89490-071-4, and from Peter Jenniskens’s book, “Meteor Showers and Their Parent Comets”, Cambridge University Press, Cambridge UK, ISBN 139780521853491.
Related Sites for List of meteor showers
Meteor burst communications
The distance over which communications can be established is determined by the altitude at which the ionization is created, the location over the surface of the Earth where the meteor is falling, the angle of entry into the atmosphere, and the relative locations of the stations attempting to establish communications. Because these ionization trails only exist for fractions of a 2nd to as long as a few seconds in duration, they create only brief windows of opportunity for communications.
The earliest direct observation of interaction between meteors and radio propagation was reported in 1929 by Hantaro Nagaoka of Japan. In 1931, Greenleaf Pickard noticed that bursts of long distance propagation occurred at times of major meteor showers. At the same time, Bell Labs researcher A. M. Skellett was studying ways to improve night-time radio propagation, and suggested that the oddities many researchers were seeing were due to meteors. The next year Schafer and Goodall noted that the atmosphere was disturbed during that year’s Leonid meteor shower, prompting Skellett to postulate that the mechanism was reflection or scattering from electrons in meteor trails. In 1944, while researching a radar system that was “pointed up” to detect the V-2 missiles falling on London, Hay confirmed that the meteor trails were in fact reflecting radio signals.
In 1946 the U.S. Federal Communications Commission found a direct correlation between enhancements in VHF radio signals and individual meteors. Studies conducted in the early 1950s by the National Bureau of Standards and the Stanford Research Institute had limited success at actually using this as a medium.
One of the 1st major deployments was “COMET”, used for long-range communications with NATO’s Supreme Headquarters Allied Powers Europe headquarters. COMET became operational in 1965, with stations located in the Netherlands, France, Italy, West Germany, the United Kingdom, and Norway. COMET maintained an average throughput between 115 and 310 bits per second, depending on the time of year.
Meteor burst communications faded from interest with the increasing use of satellite communications systems starting in the late 1960s. However, in the late 1970s it became clear that the satellites were not as universally useful as originally thought, notably at high latitudes or where signal security was an issue. For these reasons, the U.S. Air Force installed the Alaska Air Command MBC system in the 1970s, although it isn’t publicly known whether this system is still operational.
A more recent study is the Advanced Meteor Burst Communications System, a testbed set up by SAIC under DARPA funding. Using phase-steerable antennas directed at the proper area of the sky for any given time of day, the direction where the Earth is moving “forward”, AMBCS was able to greatly improve the data rates, averaging 4 kilobits per 2nd (kbit/s). While satellites may have a nominal throughput about 14 times greater, they’re vastly more expensive to operate.
Additional gains in throughput are theoretically possible through the use of real-time steering. The basic concept is to use backscattered signals to pinpoint the exact location of the ion trail and direct the antenna to that spot, or, in some cases, several trails at once. This improves the gain, allowing for much improved data rates. To date, this approach has not been tried experimentally, so far as is known.
The United States Department of Agriculture uses meteor scatter extensively in its SNOTEL system. Over 800 snow water content gauging stations in the Western United States are equipped with radio transmitters that rely upon meteor scatter communications to send measurements to a data center. The snow depth data collected by this system can be viewed on the Internet.
In Alaska, a similar system is used in the Alaskan Meteor Burst Communications System, collecting data for the National Weather Service from automated weather stations, as well as occasional data from other US government agencies.
Most meteor scatter communications is conducted between radio stations that are engaged in a precise schedule of transmission and reception periods. Because the presence of a meteor trail at a suitable location between two stations cannot be predicted, stations attempting meteor scatter communications must transmit the same information repeatedly until an acknowledgement of reception from the other station is received. Established protocols are employed to regulate the progress of information flow between stations. While a single meteor may create an ion trail that supports several steps of the communications protocol, often a complete exchange of information requires several meteors and a long period of time to complete.
Any form of communications mode can be used for meteor scatter communications. Single sideband audio transmission has been popular among amateur radio operators in North America attempting to establish contact with other stations during meteor showers without planning a schedule in advance with the other station. The use of Morse code has been more popular in Europe, where amateur radio operators used modified tape recorders, and later computer programs, to send messages at transmission speeds as high as 800 words per minute. Stations receiving these bursts of information record the signal and play it back at a slower speed to copy the content of the transmission. Since 2000, several digital modes implemented by computer programs have replaced voice and Morse code communications in popularity. The most popular program for amateur radio operations is WSJT, which was written explicitly for meteor scatter communications.
Related Sites for Meteor burst communications
- Meteor Burst Communications: An Additional Means Of Long-Haul … read Meteor burst communications
- meteor – definition of meteor by the Free Online Dictionary … read Meteor burst communications
- Meteor Watch read Meteor burst communications
- Radio Observing | American Meteor Society read Meteor burst communications
The Leonids is a prolific meteor shower associated with the comet Tempel-Tuttle. The Leonids get their name from the location of their radiant in the constellation Leo: the meteors appear to radiate from that point in the sky. Their proper Greek name should be Leontids (Λεοντίδαι, Leontxdai), but the word was initially constructed as a Greek/Latin hybrid and it is being used since. They peak in November.
The meteoroids left by the comet are organized in trails in orbits similar to though different from that of the comet. They are differentially disturbed by the planets, in particular Jupiter and to a lesser extent by radiation pressure from the sun, the Poynting–Robertson effect, and the Yarkovsky effect. These trails of meteoroids cause meteor showers when Earth encounters them. Old trails are spatially not dense and compose the meteor shower with a few meteors per minute. In the case of the Leonids, that tends to peak around November 18, but some are spread through several days on either side and the specific peak changes every year. Conversely, young trails are spatially very dense and the cause of meteor outbursts when the Earth enters one. Meteor storms exceed 1000 meteors per hour, to be compared to the sporadic background (5 to 8 meteors per hour) and the shower background (several per hour).
The Leonids are famous because their meteor showers, or storms, can be among the most spectacular. Because of the superlative storm of 1833 and the recent developments in scientific thought of the time the Leonids have had a major effect on the development of the scientific study of meteors which had previously been thought to be atmospheric phenomena. The meteor storm of 1833 was of truly superlative strength. One estimate is over one hundred thousand meteors an hour, but another, done as the storm abated, estimated in excess of two hundred thousand meteors an hour over the entire region of North America east of the Rocky Mountains. It was marked by the Native Americans, abolitionists like Harriet Tubman and Frederick Douglass and slave-owners and others. Near Independence, Missouri, it was taken as a sign to push the growing Mormon community out of the area. The founder and 1st leader of Mormonism, Joseph Smith, noted in his journal that the event was a literal fulfillment of the word of God and a sure sign that the coming of Christ is close at hand. Denison Olmsted explained the event most accurately. After spending the last weeks of 1833 collecting information he presented his findings in January 1834 to the American Journal of Science and Arts, published in January–April 1834, and January 1836. He noted the shower was of short duration and wasn’t seen in Europe, and that the meteors radiated from a point in the constellation of Leo and he speculated the meteors had originated from a cloud of particles in space. Accounts of the 1866 repeat of the Leonids counted hundreds per minute/a few thousand per hr in Europe. The Leonids were again seen in 1867, when moonlight reduced the rates to 1000 per hour. Another strong appearance of the Leonids in 1868 reached an intensity of 1000 per hour in dark skies. It was in 1866–67 that information on Comet Tempel-Tuttle was gathered pointing it out as the source of the meteor shower. When the storms failed to return in 1899, it was generally thought that the dust had moved on and storms were a thing of the past.
Viewing campaigns resulted in spectacular footage from the 1999, 2001 and 2002, storms producing up to 3,000 Leonid meteors per hour. Predictions for the Moon’s Leonid impacts also noted that in 2000 the side of the Moon facing the stream was away from the Earth but that impacts should be in number enough to raise a cloud of particles kicked off the Moon by impacts would cause a detectable increase in the sodium tail of the Moon. Research using the explanation of meteor trails/streams have explained the storms of the past. The 1833 storm wasn’t due to the recent passage of the comet, but from a direct impact with the previous 1800 dust trail. The meteoroids from the 1733 passage of Comet Tempel-Tuttle resulted in the 1866 storm and the 1966 storm was from the 1899 passage of the comet. The double spikes in Leonid activity in 2001 and in 2002 were due to the passage of the comet’s dust ejected in 1767 and 1866. This ground breaking work was soon applied to other meteor showers – for example the 2004 June Bootids. Peter Jenniskens has published predictions for the next 50 years. However, a close encounter with Jupiter is expected to perturb the comet’s path, and many streams, making storms of historic magnitude unlikely for many decades. Recent work tries to take into account the roles of differences in parent bodies and the specifics of their orbits, ejection velocities off the solid mass of the core of a comet, radiation pressure from the sun, the Poynting–Robertson effect, and the Yarkovsky effect on the particles of different sizes and rates of rotation to explain differences between meteor showers in terms of being predominantly fireballs or small meteors.
Predictions until the end of the 21st century have been published by Mikhail Maslov.
Related Sites for Leonids
A meteor shower is a celestial event in which a number of meteors are observed to radiate, or originate, from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth’s atmosphere at extremely high speeds on parallel trajectories. Most meteors are smaller than a grain of sand, so almost all of them disintegrate and never hit the Earth’s surface. Intense or unusual meteor showers are known as meteor outbursts and meteor storms, which may produce greater than 1,000 meteors an hour.
Because meteor shower particles are all traveling in parallel paths, and at the same velocity, they will all appear to an observer below to radiate away from a single point in the sky. This radiant point is caused by the effect of perspective, similar to parallel railroad tracks converging at a single vanishing point on the horizon when viewed from the middle of the tracks. Meteor showers are almost always named after the constellation from which the meteors appear to originate. This “fixed point” slowly moves across the sky during the night due to the Earth turning on its axis, the same reason the stars appear to slowly march across the sky. The radiant also moves slightly from night to night against the background stars due to the Earth moving in its orbit around the sun. See “IMO” Meteor Shower Calendar 2007 (International Meteor Organization) for maps of drifting “fixed points.” The radiant must be above the observer’s local horizon in order for meteors from that particular shower to be visible.
When the moving radiant is at the highest point it will reach in the observer’s sky that night, the sun will be just clearing the eastern horizon. For this reason, the best viewing time for a meteor shower is generally slightly before dawn — a compromise between the maximum number of meteors available for viewing, and the lightening sky which makes them harder to see.
Meteor showers are named after the nearest bright star with a Greek or Roman letter assigned that is close to the radiant position at the peak of the shower, whereby the grammatical declension of the Latin possessive form is replaced by “id” or “ids”. Hence, meteors radiating from near the star delta Aquarii are called delta Aquariids. The International Astronomical Union’s Task Group on Meteor Shower Nomenclature and the IAU’s Meteor Data Center keep track of meteor shower nomenclature and which showers are established.
A meteor shower is the result of an interaction between a planet, such as Earth, and streams of debris from a comet. Comets can produce debris by water vapor drag, as demonstrated by Fred Whipple in 1951, and by breakup. Whipple envisioned comets as “dirty snowballs,” composed of rock embedded in ice, orbiting the Sun. The “ice” may be water, methane, ammonia, or other volatiles, alone or in combination. The “rock” may vary in size from that of a dust mote to that of a small boulder. Dust mote sized solids are orders of magnitude more common than those the size of sand grains, which, in turn, are similarly more common than those the size of pebbles, and so on. When the ice warms and sublimates, the vapor can drag along dust, sand, and pebbles.
Each time a comet swings by the Sun in its orbit, some of its ice vaporizes and a certain amount of meteoroids will be shed. The meteoroids spread out along the entire orbit of the comet to form a meteoroid stream, also known as a “dust trail”.
Recently, Peter Jenniskens has argued that most of our short-period meteor showers aren’t from the normal water vapor drag of active comets, but the product of infrequent disintegrations, when large chunks break off a mostly dormant comet. Examples are the Quadrantids and Geminids, which originated from a breakup of asteroid-looking objects, 2003 EH1 and 3200 Phaethon, respectively, about 500 and 1000 years ago. The fragments tend to fall apart quickly into dust, sand, and pebbles, and spread out along the orbit of the comet to form a dense meteoroid stream, which subsequently evolves into Earth’s path.
The gravitational pull of the planets determines where the dust trail would pass by Earth orbit, much like a gardener directing a hose to water a distant plant. Most years, those trails would miss the Earth altogether, but in some years the Earth is showered by meteors. This effect was 1st demonstrated from observations of the 1995 alpha Monocerotids, and from earlier not widely known identifications of past earth storms.
The 1st great storm in modern times was the Leonids of November 1833. One estimate is over one hundred thousand meteors an hour, but another, done as the storm abated, estimated in excess of two hundred thousand meteors an hour over the entire region of North America east of the Rocky Mountains. American Denison Olmsted explained the event most accurately. After spending the last weeks of 1833 collecting information he presented his findings in January 1834 to the American Journal of Science and Arts, published in January–April 1834, and January 1836. He noted the shower was of short duration and wasn’t seen in Europe, and that the meteors radiated from a point in the constellation of Leo and he speculated the meteors had originated from a cloud of particles in space. Work continued, however, coming to understand the annual nature of showers though the occurrences of storms perplexed researchers.
In the 1890s, Irish astronomer George Johnstone Stoney and British astronomer Arthur Matthew Weld Downing (1850–1917), were the 1st to attempt to calculate the position of the dust at Earth’s orbit. They studied the dust ejected in 1866 by comet 55P/Tempel-Tuttle in advance of the anticipated Leonid shower return of 1898 and 1899. Meteor storms were anticipated, but the final calculations showed that most of the dust would be far inside of Earth’s orbit. The same results were independently arrived at by Adolf Berberich of the Kxnigliches Astronomisches Rechen Institut (Royal Astronomical Computation Institute) in Berlin, Germany. Although the absence of meteor storms that season confirmed the calculations, the advance of much better computing tools was needed to arrive at reliable predictions.
In 1981 Donald K. Yeomans of the Jet Propulsion Laboratory reviewed the history of meteor showers for the Leonids and the history of the dynamic orbit of Comet Tempel-Tuttle. A graph from it was adapted and re-published in Sky and Telescope. It showed relative positions of the Earth and Tempel-Tuttle and marks where Earth encountered dense dust. This showed that the meteoroids are mostly behind and outside the path of the comet, but paths of the Earth through the cloud of particles resulting in powerful storms were very near paths of nearly no activity.
In 1985, E. D. Kondrat’eva and E. A. Reznikov of Kazan State University 1st correctly identified the years when dust was released which was responsible for several past Leonid meteor storms. In anticipation of the 1999 Leonid storm, Robert H. McNaught David Asher, and Finland’s Esko Lyytinen were the 1st to apply this method in the West. Peter Jenniskens has published predictions for future dust trail encounters, resulting in meteor storms or meteor outbursts for the next 50 years. Jxrxmie Vaubaillon continues to update predictions based on observartions each year for The Institut de Mecanique Celeste et de Calcul des Ephemerides.
A 2nd effect is a close encounter with a planet. When the meteoroids pass by Earth, some are accelerated, others are decelerated (making shorter orbits), resulting in gaps in the dust trail in the next return (like opening a curtain, with grains piling up at the beginning and end of the gap). Also, Jupiter’s perturbation can change sections of the dust trail dramatically, especially for short period comets, when the grains approach the big planet at their furthest point along the orbit around the Sun, moving most slowly. As a result, the trail has a clumping, a braiding or a tangling of crescents, of each individual release of material.
When the meteoroids collide with other meteoroids in the zodiacal cloud, they lose their stream association and become part of the “sporadic meteors” background. Long since dispersed from any stream or trail, they form isolated meteors, not a part of any shower. These random meteors will not appear to come from the radiant of the main shower.
The most visible meteor shower in most years are the Perseids, which peak on 12 August of each year at over one meteor per minute. NASA has a useful tool to calculate how many meteors per hour are visible from your observing location.
The Leonid meteor shower peaks around 17 November of each year. Approximately every 33 years, the Leonid shower produces a meteor storm, peaking at rates of thousands of meteors per hour. Leonid storms gave birth to the term meteor shower when it was 1st realised, during the November 1833 storm, that the meteors radiated from near the star Gamma Leonis. The last Leonid storms were in 1999, 2001, and 2002. Before that, there were storms in 1767, 1799, 1833, 1866, 1867, and 1966. When the Leonid shower isn’t storming it is less active than the Perseids.
Official names are given in the International Astronomical Union meteor shower list.
Any other solar system body with a reasonably transparent atmosphere can also have meteor showers. For instance, Mars is known to have meteor showers, although these are different from the ones seen on Earth because the different orbits of Mars and Earth intersect orbits of comets in different ways.
Although the Martian atmosphere has less than one percent of the density of Earth’s at ground level, at their upper edges, where meteoroids strike, the two are more similar. Because of the similar air pressure at altitudes for meteors, the effects are much the same. Only the relatively slower motion of the meteoroids due to increased distance from the sun should marginally decrease meteor brightness. This is somewhat balanced in that the slower descent means that Martian meteors have more time in which to ablate.
On March 7, 2004, the panoramic camera on Mars Exploration Rover Spirit recorded a streak which is now believed to have been caused by a meteor from a Martian meteor shower associated with comet 114P/Wiseman-Skiff. A strong display from this shower was expected on December 20, 2007. Other showers speculated about are a “Lambda Geminid” shower associated with the Eta Aquariids of Earth, a “Beta Canis Major” shower associated with Comet 13P/Olbers, and “Draconids” from 5335 Damocles.