Enjoying EarthSky? Subscribe.

121,372 subscribers and counting ...

By in
| | Astronomy Essentials | Space on Dec 10, 2014

Radiant point for December’s Geminid meteor shower

The December Geminid meteor shower radiates from the constellation Gemini – in the east in mid-evening or overhead by about 2 a.m.

Where do you look to see December’s famous Geminid meteor shower? Simply look in an open sky, in no particular direction. That’s because these meteors fly in many different directions and in front of numerous age-old constellations. But meteor showers do have radiant points. That is, if you trace the paths of the Geminid meteors backward, they all appear to radiate from a point in the constellation Gemini the Twins. Do you need to find Gemini to watch the shower? No, but it’s fun to spot the radiant point in the night sky. Follow the links below to learn more about the Geminid shower, and its radiant point.

Why do meteor showers have radiant points?

Where is the radiant point for the Geminid shower?

When can I see Geminid meteors in 2014?

How many Geminids meteors might I see in 2014?

What is the origin of the Geminid meteor shower?

When you stand gazing along a railroad track, you see the illusion of tracks converging in the distance.  LIke the railroad tracks, meteors entering Earth's atmosphere are on parallel paths.  But, if you trace their paths backwards, the paths of meteors in a single shower appear to converge at a point on the sky's dome.  This is the shower's radiant point.

When you stand gazing along a railroad track, you see the illusion of tracks converging in the distance. Like the railroad tracks, meteors entering Earth’s atmosphere are on parallel paths. But, if you trace their paths backwards, the paths of meteors in a single shower appear to converge at a point on the sky’s dome. This is the shower’s radiant point.

Why do meteor showers have radiant points? No matter where you are on the globe, expect the most Geminids to streak the night from about 1 a.m. to 3 a.m. local time. That’s when the Geminids’ radiant point climbs highest in the sky.

What is a radiant point? Remember, the meteors are arriving from outer space. When we see them, it’s as though we’re standing in the middle of railroad tracks, gazing down the tracks and watching them converge in the distance. Meteor shower radiant points are kin to this illusion.

They’re really arriving on parallel paths. But, to us on Earth’s surface, their paths appear to converge in the distance.

Where is the radiant point for the Geminid shower? The Geminid shower radiates from the constellation Gemini the Twins, as shown on the chart above. That’s how this shower got its name. The meteors come from a point near the star Castor in Gemini, one of the brightest stars in the sky. If you watch this shower – and trace the paths of the meteors backwards on the sky’s dome – you’ll find that the meteor paths seem to converge at a point in the sky near this star.

To see Castor, look fairly low in the east-northeast sky around 9 p.m. This star is noticeable for being bright and near another star of almost equal brightness – its brother star in Gemini – called Pollux. The stars Castor and Pollux, and the Geminid meteor shower radiant, swing upward through the night and climb pretty much overhead by around 2 a.m. That’s what’s important about a meteor shower’s radiant point: the higher the radiant rises into in your sky, the more meteors you’re likely to see.

That means you can expect to see the most Geminids around 2 a.m., when Castor will be highest in the sky, and the meteors will be raining down from overhead.

Photo via Flickr user Navicore.

Photo via Flickr user Navicore.

When can I see Geminid meteors in 2014? The Geminid shower comes on strong around this time every year. In 2014, the best nights will be December 12-13 and 13-14, with the nod going to December 13-14.

No matter where you live worldwide, the greatest number of Geminid meteors usually fall after midnight. But you can watch this shower in late evening as well. Fortunately, in 2014, the waning moon shouldn’t dampen this year’s production too greatly.

In 2014, the morning of Saturday, December 14, will probably stage the peak of the Geminid shower. But look for a couple nights before then as well, and during the evening hours before moonrise. Click here to find out the moon’s rising time in your sky.

How many Geminids meteors might I see in 2014? You never know for sure which part of the world will win the prize. From everywhere worldwide, look for the meteors to fall most abundantly in the wee hours after midnight, centered on 2 a.m. local time. The waning moon will be in the way then, but even so, there’s a reasonable good chance of seeing up to 50 meteors per hour. The moderately fast Geminid meteors tend to be bright. These meteors should be bright enough to offer a little extra holiday lighting on these cold December nights.

What is the origin of the Geminid meteor shower? Meteors in annual showers – like the Geminids – stem from debris left behind by comets as they orbit the sun. A meteor shower’s radiant point represents the direction in the sky at which Earth’s orbit intersects the orbit of that (usually) long-lost comet.

The parent object of the Geminids is very special. It looks more like an asteroid than a comet, and it has an asteroid name: 3200 Phaethon. Perhaps the link between comets and asteroids is closer than we think! Plus, in recent years, astronomers have been contemplating a new name for objects like 3200 Phaethon. Some are calling them rock comets.

Bottom line: You don’t need to find the radiant point for a meteor shower to see the meteors. But it’s fun to locate the radiant in the sky. This post tells you how to find the radiant point for the December Geminid meteor shower. Watch the shower on the nights of December 12-13 and 13-14. Just lie back comfortably and let your gaze wander to all parts of the sky.

EarthSky’s meteor guide for 2014

Castor is the fainter of the two Twin stars