Modest Geminid Meteor Shower this Weekend

Space.com ^ | 12 December 2003 | Joe Rao

[ForGod'sSake]

	Modest Geminid Meteor Shower this Weekend By Joe Rao SPACE.com's Night Sky Columnist posted: 07:00 am ET 12 December 2003

The typically reliable Geminid meteor shower will peak this weekend. There

will be some windows of opportunity for good viewing, but unfortunately much

of the show will be seriously hindered by moonlight.

A bright gibbous Moon will have already come over the east-northeast horizon

by 10 p.m. on Saturday evening, Dec. 13 for most locations and will light up

the sky through the rest of the overnight hours. This moonlight will overpower

many of the shooting stars associated with one of the best annual meteor displays

presently visible from Earth.

NightSky Friday

Visit SPACE.com each Friday to explore a new backyard astronomy feature.

>>Go to NightSky Friday archive page

Images

The

Geminid radiant on Dec. 13 at 9 p.m. from mid-northern latitudes. Meteors

can appear anywhere in the sky, but if you trace each path backward it will

point at the radiant.

* Graphic made with Starry Night Software

Related SPACE.com STORIES

	What's Up Tonight

	Meteor Observing Tips and Shooting Star Glossary

	Does Anyone Ever Get Hit by Meteors?

	Meteors and Meteor Showers: How They Work

TODAY'S DISCUSSION

What do you think of this story?

>>Uplink your views

For those willing to brave the chill, the Geminids are typically a fine winter

shower, and usually the most satisfying of all the annual showers, even surpassing

the August Perseids.

"If you have not seen a mighty Geminid fireball arcing gracefully across

an expanse of sky, then you have not seen a meteor," write astronomers David

Levy and Stephen Edberg.

The Geminids stand apart from other meteor showers in another way: The meteors

seem to have been spawned not by a comet, but by 3200 Phaeton, an asteroid that

crosses the orbit of Earth. Then again, the Geminids may be comet debris after

all, for some astronomers consider Phaeton to really be the dead nucleus of

a burned-out comet that somehow got trapped into an unusually tight orbit.

Shower underway

Whatever its origins, the Geminids have a reputation for being rich both in

slow, bright, graceful meteors and fireballs as well as faint meteors, with

relatively fewer objects of medium brightness. Many appear yellowish in hue.

Some even seem to form jagged or divided paths.

Because Geminid meteoroids are several times denser than the cometary dust

flakes that supply most meteor showers, and because of the relatively slow speed

at which they encounter Earth (22 miles per second, or 35 kilometers per second),

Geminid meteors appear to linger a bit longer than most.

The shower has already begun.

The Earth moves quickly through this meteor stream, producing a somewhat broad,

lopsided activity profile. Hourly rates started to increase steadily this past

Wednesday, appearing roughly above a quarter of their peak strength. Were it

not for the Moon’s interference late Saturday night into Sunday morning, a single

observer might average as many as one or two meteor sightings per minute.

After Saturday night, the rates are expected to drop off more sharply, but

there is good reason to keep watching for Geminids even after their peak has

passed, for those "late" Geminids, tend to be especially bright. Renegade

late stragglers might be seen for a week or more after the night of maximum

activity.

These bright, medium-speed meteors appear to emanate from near the bright star

Castor, in the constellation of Gemini, the Twins, hence the name "Geminid."

The track of each one does not necessarily begin near Castor, nor even in the

constellation Gemini, but it always turns out that the path of a Geminid extended

backward along the direction of flight passes through a tiny region of sky about

0.2 degrees in diameter. In apparent size, that’s less than half the width of

the Moon. As meteor showers go, this is a rather sharply defined radiant, suggesting

the stream is "young" -- perhaps only several thousand years old.

When to watch

Generally speaking, depending on your location, Castor begins to come up above

the east-northeast horizon right around the time evening twilight is coming

to an end. So the best advice is to be out from then until moonrise when you

may catch sight of a few Geminids while the sky is still dark.

Also, as Gemini is beginning to climb the eastern sky just after darkness falls,

there is a fair chance of perhaps catching sight of some "Earth-grazing"

meteors. Earthgrazers are long, bright shooting stars that streak overhead from

a point near to or even just below the horizon. Earthgrazers are distinctive

because they follow long paths nearly parallel to our atmosphere.

With all this as a background, the best time to look for Geminids this year

will be during early-to-mid evening hours. In fact, Saturday and Sunday will

provide us with two "windows" of dark skies spanning the time between

the end of evening twilight and the rising of the Moon. Generally speaking,

there will be nearly 3 hours of completely dark skies available on Saturday

evening, increasing to almost 4 hours on Sunday. Check the table

below for examples at some selected cities.

At this time of year, meteor watching can be a long, cold business. You wait

and you wait for meteors to appear. When they don't appear right away, and if

you're cold and uncomfortable, you're not going to be looking for meteors for

very long!

Therefore, make sure you're warm and comfortable. Warm cocoa or coffee can

take the edge off the chill, as well as provide a slight stimulus. It's even

better if you can observe with friends. That way, you can cover more sky. Give

your eyes time to dark-adapt before starting.

• Night

  Sky Main Page: More Skywatching News & Features

Windows of opportunity

Dark sky times for Geminid viewing Dec. 13-14

Saturday, Dec. 13

Sunday, Dec. 14

Twilight Ends

Moonrise

Window

Twilight ends

Moonrise

Window

Boston

5:53 p.m.

8:34 p.m.

161 min.

5:53 p.m.

9:42 p.m.

229 min.

Wash. DC

6:22 p.m.

9:08 p.m.

166 min.

6:22 p.m.

10:14 p.m.

232 min.

Miami

6:53 p.m.

9:50 p.m.

177 min.

6:53 p.m.

10:48 p.m.

235 min.

Chicago

6:00 p.m.

8:45 p.m.

165 min.

6:00 p.m.

9:52 p.m.

232 min.

St. Louis

6:15 p.m.

9:04 p.m.

169 min.

6:15 p.m.

10:09 p.m.

234 min.

Houston

6:48 p.m.

9:46 p.m.

178 min.

6:48 p.m.

10:45 p.m.

237 min.

Denver

6:12 p.m.

9:03 p.m.

171 min.

6:13 p.m.

10:09 p.m.

236 min.

Helena

6:30 p.m.

9:13 p.m.

163 min.

6:31 p.m.

10:24 p.m.

233 min.

Phoenix

6:58 p.m.

9:48 p.m.

170 min.

6:58 p.m.

10:49 p.m.

231 min.

Seattle

6:10 p.m.

8:52 p.m.

162 min.

6:10 p.m.

10:05 p.m.

235 min.

San Diego

6:11 p.m.

9:10 p.m.

179 min.

6:12 p.m.

10:12 p.m.

240 min.

Oakland

6:25 p.m.

9:21 p.m.

176 min.

6:25 p.m.

10:25 p.m.

240 min.

All times are local standard times. "Twilight ends" is when astronomical

twilight ends – when there is no longer any discernable horizon glow over the

southwest horizon. "Window" is the number of minutes between the time

of moonset and the end of twilight. Example: When will the sky be dark and moonless

for Geminid viewing on Saturday evening from Washington? Answer: there will

be a 166-minute period of dark skies beginning at the end of evening twilight

(6:22 p.m.) and continuing until moonrise (9:08 p.m.).

[ForGod'sSake]

I was surprised to find this NOT posted. On my way home this evening(approximately 11:00), I noticed no fewer than half a dozen streakers in about a 20 degree space between the top of the windshield and the tree line. A pretty decent show and not too late for folks on the west coast this evening...

[Porterville]

I saw a honker of a meteor at around 9:30 PST tonight

[umgud]

@9:00 PST I saw several traveling south near the Mexican border while enroute to El Centro CA.

[ForGod'sSake]

There have been some doozies. Based on the perceived direction of travel(almost perpindicular to the horizon), I wondered if it was incoming. Looked very similar to the incoming SCUD videos from Dessert Storm. Spooky.

FGS

[ForGod'sSake]

@9:00 PST I saw several traveling south near the Mexican border while enroute to El Centro CA.

Most of them would have been around your 10 o'clock position?

FGS

[ForGod'sSake]

The Geminid radiant on Dec. 13 at 9 p.m. from mid-northern latitudes. Meteors can appear anywhere in the sky, but if you trace each path backward it will point at the radiant.

FGS

[umgud]

I was going south.... didn't mean the meteors were. They were heading east to west. Sorry if I confused you. Any way......... it was a great show.