a size considerably smaller than an asteroid and considerably larger than an atom or molecule. Definition by the International Astronomical Union (1961) (i.e. the stuff between ~0.01 mm and 10 m in size) (Jenniskens, 2006)
by a 2000 kg car at 50 mph: E = ½ · 2000 kg · (22 m/s)2 = ~500 000 Joule Getting hit by a 0.5 g meteoroid at 100 000 mph: E = ½ · 0.0005 kg · (45 000 m/s)2 = ~500 000 Joule
4% of light Jets of sublimating ices 79% H2 O, 13% CO, 3% H2 CO, 3% CO2 Dust particles most likely dragged along by jets; pushed to slightly different orbits. (video)
streams really look like! Key insights: 1) Comet trajectories change every revolution (slightly or dramatic) 2) Trails can remain narrow for decades to centuries (dispersion due to gravity and radiation pressure often a slow process!)
megarod Sensitivity @ 50 fps 10-6 ~ 10-7 lux (1 - 4th magnitude) 10-8 lux (6th magnitude) Dynamic range 1 : 1 000 ~1 : 1 000 000 000 (delay) Why use our eyes when we have video cameras?! Answer: the human eye is incredibly sensitive to faint, fast-moving objects!
way that they can easily be understood "in 20 years from now" • Your full name and location • Date (e.g. "Night from 8 to 9 October 2011") • Timezone used (!) • Meteor showers you will classify • Starting time of the observation
meteors), we need to know: 1) Sky quality ("limiting magnitude") 2) Number of meteors per shower 3) Brightness of each meteor (optional) For example: 20:04 - 20:12 UT Limiting magnitude = 5.2 2 Draconids (mag. 1 & mag. 3) 1 Sporadic (mag. 4)
'reference fields' (include corner stars) 2. Look up the corresponding Limiting Magnitude (Lm) in the tables at www.imo.net Stars in field #14 Limiting magnitude 1 2.23 2 2.49 3 3.90 4 4.65 5 4.73 ... ... 1. Estimate the sky quality Your count needs to be independent, do not be influenced by colleagues!
shower. Take into account: 1) Direction Must appear to come from within ~20 degrees of radiant 2) Length meteors near the radiant must be short 3) Speed Draconids are very slow! Note: 5 to 15 meteors per hour do not belong to any known shower; we classify these as „sporadic“.
objects, e.g.: Make a best-effort estimate - do not be afraid to be wrong, and do not listen to your colleagues! Object Magnitude Full Moon - 13m Jupiter -3m Sirius -1.5m Vega 0m Aldebaran 1m Polaris 2m
October 1933. "Just before 7 pm, I observed a brilliant meteor drop from the constellation Lyra. Five minutes later I counted a dozen meteors during the few minutes occupied in walking up the Observatory avenue. Between 7 and 7-35 pm I counted 300 meteors. ... Called indoors for the evening meal at 7-35. I was out again at 7-58. Then it was apparent that a really great meteoric storm was in progress. I counted 200 meteors in two minutes, and then counting became impossible. The fire- stars became as thick as the flakes of a snowstorm.“ This event was followed by another major outburst in 1946 (Ellison died 1936), and smaller peaks in 1952 (250/hr), 1985 (550/hr) and 1998 (500/hr).
18:00 BST 1894 19:03 BST 1900 21:11 BST Predictions for 2011 by multiple scientists agree with respect to the timing (Credit: Watanabe & Sato, Vaubaillon, Maslov, Cooke & Moser, et al.) Confirmation by David Asher: Uncertain (comet not observed). Meteors might be bright. Trail known to exist, ZHR 60-600? Meteors likely faint. Solar altitude Time 0 (Sunset) 18:45 BST -6 (Civil) 19:23 BST -12 (Nautical) 20:03 BST -18 (Astronomical) 20:45 BST Darkness in Armagh:
< m+1 = population index r # m < 3.5 # m < 6.5 = r^3 = 3^3 = 27 Worst case: Draconids r = 3.0 (uncertain) and Limiting Mag. = 3.5; We would only see 1 out of every 27 meteors! (ZHR 600 => 22 ) Magnitude Meteors 0 1 2 3 4 5 6 x r x r x r x r x r x r „power-law“ Sky quality
trails which caused the major storms in 1933 & 1946! 2) The 1933 & 1946 storms ALSO took place under a full moon! ... but, the trail is more dispersed now! (how much?!)
& 1946? • Where was the comet before its discovery in 1900? • When did it lose most material? • How did the dust spread out? • Does the stream contain large grains? This meteor shower will teach us about the comet and the likelihood of future outbursts! (e.g. 2018, 2037) Two aircrafts will be deployed! (Vaubaillon et al.)
brighter appeared in a momentary splendour. These exceptional objects had long luminous trains which lasted for a few seconds after the meteor had vanished. Also the character of their light was very bright, diamond- like, and sparkling.“ Let's hope for 1 or 2 beautiful fireballs, and be happy with any extras! 1933 Belfast Telegraph:
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