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There float in the vast reaches of our Solar System swarms of sand bits
and dust clods known as meteoroids. When these "space debris"
tear into the Earth's atmosphere, air friction causes them to burn,
forming momentary bright streaks that blaze across the sky. These are the
meteors that we see from time to time.
Meteors often appear as sporadic lonely streaks that traverse somewhat
random paths in the sky. This sporadic activity, which persists throughout
the year, can account for about 10 visible meteors every hour on a clear
night.
A
"meteor shower" occurs when our home planet encounters a
relatively dense region of meteoroids in space. An unusually large number
of meteors can then be seen streaming from a certain point in the sky
known as the "radiant". Most astronomers believe that meteoroids
are of cometary origin. They are leftovers from periodic comets or are
even fragmented comet nuclei. This at least accounts for the fact that a
particular group of meteoroids shares with its parent comet more or less
the same orbit, which can remain relatively unchanged over eons. An
immediate consequence is that our Earth makes periodic rendezvous with
this meteoroid swarm, thereby culminating in a regular display of these
celestial fireworks. To name a few, we have the Lyrids in April and the
Geminids in December.
It is not uncommon that meteor
showers are not spectacular at all, with the number of observed meteors
barely surpasses the normal hourly rate. Needless to say, this may
disappoint stargazers who hold high expectation, but it is definitely an
unforgettable experience for those who have the luck to witness a truly
enormous outburst.
During the small hours of
November 13, 1833, people in Boston of the United States were terrified to
see the sky blazed with thousands of meteors and fireballs streaming from
the constellation Leo. (It was estimated that over 150 000 meteors were
visible per hour). While many religious devotees believed that the
Judgment Day had finally arrived, some even went so far as to commit
suicide.
Major Meteor Stream
|
Shower
|
Radiant
|
Duration
|
Maximum
|
Speed (km/s)
|
Zenith Hour Rate (ZHR)
|
Associated Comet
|
|
R.A.
|
Decl.
|
D/M-
D/M
|
D/M
|
| Quadrantids |
232 |
+50 |
01/01
- 05/01 |
04/01 |
41 |
85 |
|
| Lyrids |
271 |
+34 |
19/04
- 25/04 |
21/04 |
49 |
10 |
1861I |
| Eta
Aquarids |
338 |
-01 |
19/04
- 28/05 |
05/05 |
66 |
35 |
Halley |
| Southern
Iota Aquarids |
339 |
-16 |
12/07
- 19/08 |
28/07 |
41 |
8 |
|
| Alpha
Capricornids |
307 |
-10 |
03/07
- 15/08 |
02/08 |
23 |
5 |
|
| Northern
Iota Aquarids |
335 |
-05 |
15/07
- 25/08 |
08/08 |
42 |
10 |
|
| Perseids |
46 |
+58 |
23/07
- 20/08 |
12/08 |
59 |
75 |
Swift-Tuttle |
| Orionids |
95 |
+16 |
02/10
- 07/11 |
22/10 |
66 |
25 |
Halley |
| Leonids |
153 |
+22 |
14/1
- 21/11 |
18/11 |
71 |
100? |
Tempel-Tuttle |
| Geminids |
112 |
+33 |
07/12
- 16/12 |
14/12 |
35 |
75 |
Asteroid
3200 |
Download "Visual Meteor
Observation Report Form"PDF format
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