Nationwide Geminid Watch 2009
Astronomy is one of the few areas where amateurs can make a real contribution to science. You might think that you need to be an 'expert' to contribute data which will have real scientific value. This could not be further from the truth.
This year Astronomy Ireland is urging everybody to count meteors (shooting stars) between December 11th and 15th. This nationwide count coincides with the maximum of the Geminid meteor shower.
The Geminids are a particularly interesting meteor shower as the numbers of meteors observed per hour (the Zenithal Hourly Rate, or ZHR) actually appears to be increasing each year. Meteors are often called 'shooting stars' but in reality, meteors are not connected with stars at all. In fact they are tiny pieces of debris (often no bigger than a grain of sand) which hit our atmosphere at very high speed and instantly vaporise. Geminid meteors are in fact tiny pieces of an unusual comet-like asteroid known as 3200 Phaethon. Each year our planet intersects the stream of debris which is left behind by this asteroid as it orbits the Sun once every 523 days.
This year the maximum of the Geminid meteor shower occurs around the nights of December 13th/14th (Sunday night/Monday morning) and 14th/15th (Monday night/Tuesday morning). These will be the prime nights for meteor observing. However if possible observers are requested to observe on the nights of December 12th/13th and 15th/16th too. This is because meteor showers are highly unpredictable and often produce other peaks in activity which are not well known. By observing on all of these nights you may well be the person who discovers a sub-peak in meteor activity!
Of course you don't need to observe on all of these nights to produce useful data, even if you only have an hour or two to spare on one night your observations are valuable. In making such a count you are producing real scientific data which will have real value to those who study meteor showers.
You need to make your meteor count using a standard methodology which we describe below. Only if you follow the instructions given will your observation have scientific value. However, you may of course make a non-standardised observation. We will do our best to publish all observations of the Geminid meteor shower in an upcoming edition of our magazine, 'Astronomy & Space'. Before we describe the process of making a scientific count of this meteor shower, let's have a look at some general tips for observing the Geminids.
Tips for observing The Geminids
You will see the most meteors when you are well away from sources of light-pollution such as cities and towns. Aim to spend some time at a dark location in the countryside, if possible.
Don't forget to wrap up well. Many layers of lighter clothes are better than one heavy layer. A woolly or fleece hat is essential. Keep your head, hands and feet warm and you won't get too cold. If you get cold you will not enjoy the experience.
Take a flask of hot soup or tea/coffee (alcohol is a bad idea as it will actually make you colder).
A comfortable observing chair which enables you to look upwards without causing neck strain is a distinct advantage (but not essential). Seasoned meteor observers will bring a sleeping bag if they are planning a lengthy session.
If you have a pair of binoculars, take them along to observe 'trains' left behind by the brighter meteors.
IMPORTANT: On any clear night you will see many other meteors which are not Geminids. These are known as 'Sporadic' meteors. You can tell they are not Geminids because their path does not trace back to the radiant in Gemini. You should ignore these for the purposes of your count (or at least note them clearly as 'Sporadics' in your report).
The highest rates can be seen when the radiant point is highest in the sky. The radiant for the Geminids will be at its highest point at approximately 3.30am on any morning over the weekend. You can of course observer before and after this but you will see more meteors around this time. In fact, any time after midnight is usually better than before, because after midnight this side of the Earth will be facing into the cloud of dust that cause the Geminids.
The above map shows the location of the Moon for each day over the weekend. The lines in green show roughly how and where the Geminid meteors will appear. Note how they will all point back towards the constellation Gemini.
So how do I make an observation which has scientific value?
The secret is recording in some detail exactly what you see.
Before recording your observations allow about 10 minutes for your eyes to become fully dark adapted.
After 20 minutes you will need to record the following:
The percentage of sky that's visible at your locations
Which direction you are looking
How to record these is described below.
Your note should be a percentage of the total sky. Any areas which are obscured by cloud or local items like trees or buildings should be estimated and you should only note the percentage of sky you can actually see. Should this change during your session note the changes as they occur (about every half hour or so).
Now with your eyes dark adapted, your limiting magnitude and sky visibility determined, you should now sit back and start counting meteors. But which way should you face??
All meteor showers appear to radiate from a single point in the sky. During the Geminids, that point is in the constellation of Gemini, which is located in the south-east, 'above' Orion.
You now need to record each Geminid that you see noting clearly the following.
Time - Note the time to the nearest second that you saw the meteor.
Geminid or Sporadic? - Remember that all Geminids will point back towards the Moon. Sporadic meteors will radiate from elsewhere, so be sure to note clearly what kind of meteor it is.
Now here's the thing!! You need to spend as much time as possible observing meteors and not looking down at your notes. The best way to record your observations is with a portable tape recorder or other audio recording device. That way you never need to look away from the sky. If you do choose to make your notes on paper then you should also note at the end of your session, the percentage of time you spent looking at your notes instead of the sky (don't worry nobody is going to tell you off for this!). Ensure your recording device has enough capacity for the time you plan to spend observing.
We have produced a printable summary of the above and a observation log book that you can download and print and use to assist you in your observations.
Checklist
Before you set off for your meteor count check you have brought at least the following:
Warm Clothes/Sleeping Bag (as described above)
Hot Drink/Food(remember alcohol is a bad idea)
Observing Chair (also described above)
RED Torch (DO NOT use a white light torch as this will spoil your dark adaptation and if you are observing with others this will cause your companions great irritation!)
Time Piece - Bring a clock or watch which you can clearly see in the dark (with your red torch). Before you go sychronise the time with a known accurate time source such as
http://wwp.greenwichmeantime.com/. Astronomers usually use Universal Time (also known as GMT) which is currently the time we are using now (it will change in Spring).
Binoculars (Do not spend too much time looking through these as you may miss important meteors)
Recording Media - This can be a pencil and paper or preferably a tape recorder/dicta phone.
Copies of Charts given above
