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Lunar LibrationVariable Stars

Annual Meteor Showers

http://www.wolfram.com/applications/astronomer/index.html

setup

<<Astronomer`HomeSite`

shower[month_, day_, asc_, dec_] :=
Block[{h, pos, date},
pos = ChartPosition[asc, dec];
date = StringJoin[{
"Jan", "Feb", "Mar", "Apr",
"May", "Jun", "Jul", "Aug",
"Sep", "Oct", "Nov", "Dec"}[[
month]],
If[day < 10, "0", ""],
ToString[day]];
h = Mod[Round[-(1/Hour*HourAngle[{
Ascension -> asc,
Declination -> dec},
{1995,month,day}])], 24];
h = If[h > 12,
StringJoin[ToString[h-12], "pm"],
StringJoin[ToString[h], "am"]];
{{RGBColor[1, 1, 0], Disk[pos, 10]},
{RGBColor[1, 0, 0],
Text[FontForm[
StringJoin[" ", h, "\n",
date],
{"Courier", 10}], pos]}}]

{pshowers,eshowers} = Transpose[{
shower[1,3,15.3 Hour,49 Degree],
shower[4,22,18.0 Hour,34 Degree],
shower[4,23,7.3 Hour,-45 Degree],
shower[5,3,22.6 Hour,-2 Degree],
shower[7,29,22.5 Hour,-16 Degree],
shower[7,30,20.5 Hour,-10 Degree],
shower[8,12,3.0 Hour,58 Degree],
shower[10,10,17.5 Hour,54 Degree],
shower[10,22,6.3 Hour,16 Degree],
shower[11,3,3.3 Hour,14 Degree],
shower[11,18,10.1 Hour,22 Degree],
shower[12,6,1.2 Hour,-53 Degree],
shower[12,14,7.5 Hour,33 Degree],
shower[12,23,14.5 Hour,75 Degree]}];

Regular Meteor Showers

There are many meteor showers that recur each year on roughly the same date. These are due mainly to the Earth colliding with debris left along cometary orbits. A full list of such regular showers is given in the Users' Guide for Scientific Astronomer, but here is a short list of the main showers.

SHOWER-NAME PEAK [RANGE] (RADIANT) (ZHRATE)



Quadrantids Jan 03 [ -2, +2] (15h20m, +49?) (100/hour)

Lyrids Apr 22 [ -6, +3] (18h04m, +34?) (100/hour)

Pi-Puppids Apr 23 [ -8, +5] (07h20m, -45?) ( 50/hour)

Eta-Aquarids May 03 [-14,+25] (22h24m, -02?) ( 50/hour)

Delta-Aquarids S Jul 29 [-21,+21] (22h36m, -16?) ( 20/hour)

Alpha-Capricornids Jul 30 [-27,+26] (20h28m, -10?) ( 10/hour)

Perseids Aug 12 [-26,+12] (03h04m, +58?) (100/hour)

Draconids Oct 10 [ -4, +0] (17h28m, +54?) ( STORM)

Orionids Oct 22 [-20,+16] (06h20m, +16?) ( 20/hour)

Taurids S Nov 03 [-49,+22] (03h20m, +14?) ( 10/hour)

Leonids Nov 18 [ -4, +3] (10h08m, +22?) ( STORM)

Phoenicids (Dec) Dec 06 [ -8, +3] (01h12m, -53?) (100/hour)

Geminids Dec 14 [ -7, +3] (07h28m, +33?) (100/hour)

Ursids Dec 23 [ -6, +3] (14h28m, +75?) ( 50/hour)

Most showers peak on a particular date, but there can be a wide range of dates. For example, the Lyrids shower peaks on April 22, but is around for roughly 6 days before and 3 days afterwards as indicated in the table.

Each shower will appear to come from a particular point in the sky, known as the radiant.

The best time for viewing meteors in general is after midnight (and before dawn). The reason there are more meteors after midnight is that the Earth is moving head-on into any space debris at that time.

On an average night there are about 10 meteors per hour with a magnitude brighter than 5 (which is about as faint as you can see under good conditions). During a shower there are considerably more meteors per hour, and what is more they will all eminate from one small radiant in the sky which makes them easier to find.

Full Sky

In the following graphic the position of the main meteor showers are shown as yellow disks. The peak date for a shower is written in red text, and above that is the hour that the radiant is highest in the sky, that is when the radiant is either due-south (for Northern hemisphere observers) or due-north (for Southern hemisphere observers).

StarChart[PrologRulepshowers,
EpilogRuleeshowers];1;

Northern Hemisphere

The following graphic shows the meteor showers that are most easily visible from the Northern hemisphere.

RadialStarChart[NorthCelestialPole,
RadialAngleRule120 Degree,
PrologRulepshowers,
EpilogRuleeshowers];1;

The Ursids shower, on December 23, has a radiant very near the North Celestial Pole. That shower can therefore be observed throughout the night in the Northern Hemisphere.

Southern Hemisphere

The following graphic shows the meteor showers that are most easily visible from the Southern hemisphere.

RadialStarChart[SouthCelestialPole,
RadialAngleRule120 Degree,
PrologRulepshowers,
EpilogRuleeshowers];1;

The Leonids shower, on November 18, is highest in the sky at 7am in the morning. Because this shower is near the celestial equator the radiant will rise above the horizon roughly 6 hours earlier at say 1am and similarly set into the opposite horizon at say 1pm. The Leonids showers can therefore be observed only between 1am and sunrise.

Lunar LibrationVariable Stars



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