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Friday, December 11, 2015


Geminid Meteor Shower 14-15 December 2015

The northern horizon at 4:00 am ACDST as seen from Adelaide on Tuesday December 15. The Geminid radiant is marked with a starburst. Similar views will be seen elsewhere in Australia at  a similar latitude and the equivalent local time. (click to embiggen).The northern horizon at 3:00 am AEDST as seen from Sydney on Tuesday December 15. The Geminid radiant is marked with a starburst. Similar views will be seen elsewhere in Australia at  a similar latitude and the equivalent local time. (click to embiggen).

The Geminids are unusual meteor shower in that their parent body is 3200 Phaethon, an asteroid, rather than a comet. It is speculated though that Phaeton is actually a "gassed out" comet, and so the debris that makes up the Geminids may still be cometary particles.
The Geminids are a fairly reliable meteor shower and this year moonlight will not interfere, and some decent meteors rates should be seen. 

Unlike the Leonids, where there is a very narrow peak of high activity, the Geminids have a broad peak and will show good activity well before and after the peak, and on the day before and after. The peak is December 14, 18h00m UT. That is 5 am AEDST December 15 in Australia.  This is in twilight in most of Australia, but levels should be ramping up before twilight so you should get decent rates. However, the radiant doesn't rise until just before midnight (daylight saving time) in most of Australia, so you will still have to disturb your sleep for this one. 

Australians should see a meteor every two to three minutes under dark skies in the early morning of the 15th, between 1:00 am and 4:00 am local daylight saving time. You can find predictions for your local site at the meteor flux estimator (choose 4 Geminids and date 14-15 December, don't forget to change the date to 2015). 

At 1.00 am in the morning AEDST (midnight, AEST) Castor (alpha Geminorum) is about two hand-spans above the horizon and 10 hand-spans to the right of due north. Pollux, the other twin, is less than a hand-span to the right again. The radiant is just below Pollux.

When you get up, allow at least 5 minutes for your eyes to adjust and become dark adapted (even if you have stumbled out of bed in the dark, here's some hints on dark adaption of your eyes so you can see meteors better) and be patient, it may be several minutes before you are rewarded with you first meteor, then a couple will come along in quick succession (a meteor every three minutes is an average, they won't turn up like a ticking clock but more or less randomly).

Choose a viewing spot where you can see a large swathe of sky without trees or buildings getting in the way, or with street lights getting in your eyes. The darker the spot the better (but do be sensible, don't choose a spot in an insalubrious park for example). While the radiant is where the meteors appear to originate from, most of the meteors will be seen away from the radiant, so don't fixate on the radiant, but keep your eye on a broad swath of sky roughly centred just above the radiant (as the radiant doesn't rise very high, looking exactly at the radiant will mean you miss some higher up).

A lawn chair or something similar will make your observing comfortable (or a picnic rug spread on the ground and a nice pillow), and having a Thermos of hot coffee, tea or chocolate to swig while watching will increase your comfort. Despite it being summer, make sure you have a jumper or something as the night can still get cold

Guides to taking meteor photos are here and here.

As well, Orion and the Hyades will be visible and bright Jupiter and Venus (and less bright Mars) will be nearby. So it will be a quite nice morning for sky watching. Keep an eye out for satellites!

Cloud cover predictions can be found at SkippySky.  

Here is the near-real time satellite view of the clouds (day and night) http://satview.bom.gov.au/


Geminids is said to be the king of meteor showers, therefor according to some websites they are expecting to see 200 meteors per hour on 13-14 of December? How true is this?

Thank You
Not true at all, according to the International Meteor Organisation the peak should be 120 meteors and hour, peaking on 14 December 1800 H UT (this is around 5 am on the 15th in Australia)
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