Geminid Meteor Shower
Time for meteor shower again!
When it’s December, it’s Geminids time.
Geminids is one of the best meteor shower of the year and seldom disappoint observers. It usually produces 50 or more meteors an hour, sometimes even up to 100 or more. Unfortunately this year, during its peak on December 13/14, a full moon will washed out all but the brightest meteors.
You can start to look out for geminids as the radiant rises in the east around 9:30 pm on December 13/14; or you can wait for an hour or two for the radiant to rise higher in the sky to increase your chances of spotting a geminid. Geminids are medium-speed meteors, about 35 km/s, half as slow as the Leonids. This makes them fairly easy to spot. The brighter ones sometime are coloured.
Not all meteors that you see will be geminids though; some may be sporadic (or random) meteors. How do you differentiate between a geminids and a sporadic?
It’s simple. Just trace back the path of the meteor and see if it ends up in constellation Gemini. If yes, then it’s a geminid; if not, then it is just a sporadic meteor.
You don’t really need to wait for December 13/14 to see geminids; meteor shower, unlike most sky events, happens for a period of time spanning weeks instead of just a day or a few hours. Geminids can be visible as early as December 7 – although the rate is low at about one meteor per hour. The numbers of meteor will slowly build-up until it peak on December 13/14 and then decline. The last can be seen maybe until December 17.
Most well known meteor showers, like the perseids and leonids, are old. The geminids, on the other hand, are young; they were first observed only 150 years ago in the mid-1800s. After searching for more than 100 years for geminids’ parent object, we finally discovered a curious object with an orbital period of 1.4 years moving in the same orbit as the geminid meteoroid stream. This was discovered through NASA’s Infrared Astronomical Satellite in 1983.
To the surprise of many it wasn’t a comet, but a rocky asteroid now known as 3200 Phaethon. So geminids are special in the sense that they do not originate from a comet like almost all the other meteor showers.
This then raises a question: how does an asteroid that is made of tougher stuff produce a meteoroid debris stream?
Our common understanding is that as a comet, which is primarily composed of ice and dust, when passes close to the Sun, the heat will evaporate its ice. This icy, dusty debris stream will then be distributed along the comet’s orbit. As our Earth passes through the stream, these left-over comet debris will bombard Earth and cause the rate of meteors to increases, and thus a meteor shower.
But an asteroid doesn’t have ice like a comet…
One of the earliest ideas was that Phaethon might occasionally collide with other asteroids and created a meteoroid stream. It is also possible that when Phaethon passes by the Sun bits and pieces do break off to form the geminid meteoroids. However, now many astronomers believe that Phaethon is an extinct or dormant comet.
Whatever it is, it will not stop up us from enjoying the sky show, right? So hopefully the weather will be fine and clear skies to everyone out there!
Click here for some tips on how to observe meteor shower. To learn more about meteor and meteor shower, go to Meteor Shower ABC.