[Pollux]

Hi all,
Popping in & out last night between cloud, I managed to watch 2 Geminids (nothing spectacular I know, but will lead to a question) @ around 11.25 to 11.45pm…

The first appeared to the right of Castor, heading towards Mebusta – this one was a bright white colour and travelling relatively ‘fast’.
The second appeared to the left and below Pollux, now this one headed in the exact opposite direction, was an orange/yellow colour and appeared to be travelling relatively ‘slow’.

The question.
I was under the impression the Geminids are remnants of a comets tail, and thus still travelling in the comets’ original orbit? if that’s the case, why the different directions – I would expect them all to ‘travel’ in the same direction?
Or, is it a totally random thing (here there n everywhere) bouncing thro the atmosphere???
I’m presuming the difference in colour is due to a difference in meteoroid size? orange=bigger/slower, white=smaller/faster???

No,I hadn’t had a drink!

Your thoughts appreciated…
…Mark

[barkis]

Mark,
I believe the peak of the Geminids is tonight and early Monday morning. What you saw was perhaps a couple of sporadic meteors.
You are correct in that they are the debris from a passing comet, but that trail over time becomes quite spread out, and the earth will pick up the fringe stuff from the main stream prior to the main encounter tonight and Sunday morning.
Ron.

[keithatrochdale]

We were lucky to see quite a number last night, whetted our appetite for to-night, but it may not be so clear.

[brianb]

I believe the peak of the Geminids is tonight and early Monday morning. What you saw was perhaps a couple of sporadic meteors.
You are correct in that they are the debris from a passing comet

The description is consistent with Geminids. The peak may be on Monday morning but there is activity from the 9th to the 16th (British Astronomical Handbook).

Stand on a motorway bridge looking at the oncoming traffic - some vehicles pass to your left appearing to go further left, some to your right appearing to go further right (depending on which lane they're in), nevertheless they're all going in pretty much the same direction. The same applies with meteors, they appear to come from a small patch which is where the excometary orbit is bringing them from, but they're not all aimed straight at you, so you see them in all parts of the sky heading in all sorts of directions - but, for Geminids, if you project the path back, they'll all come from a small patch of sky near Castor.

A meteor that doesn't appear to come from somewhere near Castor is a sporadic or a member of another minor shower (there may be half a dozen minor showers active on any given night).

[hunterknox]

Hi Mark,

Here's my long attempt at an explanation...

Meteor showers result from the earth passing through the trails of dust left behind by comets. What we see is tiny particles of dust (usually about the size of a grain of sand, but sometimes bigger), burning up in our atmosphere.

My somewhat tortured analogy is this: Imagine you're in the middle of a transparent football that gets kicked through a patch of midges. You'd see some whizz over you and some whizz under you; some to the left and some to the right, but they'd all appear to come from the same point, known as 'radiant', which is in the ball's direction of travel.

Going back to meteors, each shower has a radiant point, which reflects the Earth's direction of travel through the dust trail (and to some extent, any bulk motion of the dust)

You can see from this gorgeous picture that meteors in the same shower should go in different directions providing they're on different sides of the radiant.

Here's a picture of where to find the Geminid radiant. If your two meteors both came from that direction, regardless of which way they're heading, they're Geminids. If not, they're sporadic.

OK, second question. I'm not an expert on meteors, so stand to be corrected here, but my understanding is that the flash you see is not the tiny particle burning up in the atmosphere, but a trail of ionised gas, caused by frictional heating as the speck of dust careers through the atmosphere. The colour you see would depend on the amount of energy in the collision, which in turn depends on both the speed and mass of the meteor. It may also depend on the type of gas that's involved, but maybe someone with a better understanding of the atmosphere could tell us whether this is a significant?

[hunterknox]

Originally Posted by brianb

Stand on a motorway bridge...

A much neater analogy than mine!

[Pollux]

thanks guys...