Get Ready for the 2013 Geminid Meteor Shower

One of the best annual meteor showers occurs this coming weekend.

The 2013 Geminid meteors peak this coming Saturday on December 14th. This shower has a broad maximum, assuring that observers worldwide get a good look. In 2013, the maximum for the Geminids is forecast to span from 13:00 Universal Time (UT) on Friday, December 13th to 10:00UT/5:00AM EST on Saturday, December 14th, with a projected maximum centered a few hours earlier at 2:00 UT Saturday morning.

This is good news  for observers spanning both sides of the Atlantic, who should be well placed to catch the event. Keep in mind, meteor showers often peak hours before or after predictions… we certainly don’t know everything that a given meteor stream might have in store!

An all-sky composite of the 2008 Geminid meteor shower. (Credit: NASA/MSFC/Bill Cooke, NASA's Meteoroid Environment Office).
An all-sky composite of the 2008 Geminid meteor shower. (Credit: NASA/MSFC/Bill Cooke, NASA’s Meteoroid Environment Office).

But the time to start watching is now. We’ve already seen a few early Geminids this past weekend, and this shower is notable for showing early activity for northern hemisphere observers before local midnight. This is because the radiant, or the direction that the meteors seem to emanate from lies at a high northern declination of 33 degrees north near the star Castor, also known as Alpha Geminorum.

The typical Zenithal Hourly Rate for the Geminids is 80-120, or about 1 to 2 per minute. Keep in mind, the ZHR is an ideal rate, assuming dark skies, with the radiant positioned directly overhead. Most observers will see significantly less activity.

The 2013 Geminids also have to contend with the waxing gibbous Moon, which reaches Full just 3 days after the shower’s expected maximum. This will give observers a dwindling window between moonset and the start of dawn twilight to catch the Geminids at their best.

We always thought that the Geminids had a bit of an undeserved PR problem among annual showers. This no doubt stems from the fact that they arrive in the chilly month of December, a time when fingers go numb, camera batteries die, and conducting a vigil for meteors is challenging.

A 2012 Geminid captured by the author from Mars Hill. North Carolina.
A 2012 Geminid captured by the author from Mars Hill, North Carolina.

This shower is an interesting one though, with an equally interesting history and source. The Geminids were first identified as a distinct meteor shower by R.P. Greg of Manchester UK in 1862, and the estimated ZHR rose from about 20 to 80 through the 20th century. The parent source of the Geminids remained unknown until 1983, when astronomer Fred Whipple linked them to the strange “rock-comet” body 3200 Phaethon. An Apollo asteroid also thought to be a member of the Pallas family of asteroids, 3200 Phaethon seems to be shedding enough material to produce the annual Geminid meteor shower. This makes the annual shower rare as one not produced by a comet. It’s worth noting that 3200 Phaethon also passes extremely close – 0.14 AU – from the Sun at perihelion, and gets periodically “baked” during each 1.4 year passage.

In the 21st century, rates for the Geminids have stayed above a ZHR of 120, currently the highest of any annual shower. It’s worth noting that an extrapolated ZHR of almost 200 were seen in 2011 when the Moon was at an equally unfavorable waning gibbous phase! The Geminids always produce lots of fireballs, capable of being seen even under moonlit skies.

There are also two other showers currently active to watch for this week. One is the Ursid meteors, which radiate from the Little Dipper (Ursa Minor) with a peak ZHR of 10-50 occurring on December 22nd. Also, keep an eye out for Andromedid meteors this week, a defunct shower that may be making a comeback. The source of several great meteor storms in the late 19th century, the Andromedid parent source is the shattered comet formerly known as 3D/Biela.

An early Geminid crosses pathes with Comet 2013 R1 Lovejoy. (Credit: Jason Hullinger).
An early Geminid crosses paths with Comet 2013 R1 Lovejoy. (Credit: Jason Hullinger).

Though the Geminids appear to radiate from the constellation Gemini, they can appear anywhere in the sky. Tracing the path back can determine the source constellation and the “membership” of a given meteor. Random meteors not associated with any identified shower are known as “sporadics.” Block that pesky light-polluting Moon behind a building or hill to optimize your chances of catching sight of a meteor. Employing a friend or two to watch in different directions will also maximize the number seen. The International Meteor Organization always welcomes reports from observers… this is real science that you can contribute to using nothing more sophisticated than your eyes!

The Geminids are medium-speed meteors with an average atmospheric velocity of about 35 kilometres per second, often leaving long, glowing trails worth examining with a pair of binoculars. You might note an apparent surge in speed to this shower past local midnight, as your vantage point turns into the oncoming shower, adding the velocity of the Earth to the approaching Geminids.

Photographing meteors is fun and easy to do; all you’ll need is a DSLR camera mounted on a tripod. Take several manual setting exposures to get the combination of ISO,F-stop, and shutter speed correct for your local sky conditions.  Then simply set the focus to infinity, and use the widest field of view possible. Catching meteors is surreptitious, as they can appear anywhere – and at any time – in the sky. Be sure to thoroughly review those images afterwards… nearly every meteor we’ve caught photographically went unnoticed during observation!

Also, remember that cold weather plus long exposure times can conspire to drain camera batteries in a hurry. Be sure to keep a spare set of charged batteries ready to go in a warm pocket!

How powerful will the Geminids become? Are we in for a “return of the Andromedids” moving towards 2014? One thing is for sure: you won’t see any meteors if you don’t try. So be sure to get out there, pour a mug of your favorite warming beverage, and don’t miss the 2013 Geminid meteor shower!

–      Got meteors? Be sure and tweet ‘em to #Meteorwatch.

–      Be sure to send those pics of Geminids and more in to Universe Today.

Weekly SkyWatcher’s Forecast: August 27-September 2, 2012

Greetings, fellow SkyWatchers! If you only get your telescope or binoculars out once in a Blue Moon, then get them out this week when a Blue Moon actually happens! However, if you can’t wait, then let’s explore some great lunar features, bright star clusters and great double stars. When you’re ready to learn some history, mystery and more, then just step on inside…

Monday, August 27 – Tonight the waxing Moon’s most notable features will be the vast area of craters dominating the south-central portion near and along the terminator. Now emerging is Ptolemaeus – just north-northeast of Albategnius. This large round crater is a mountain walled plain filled with lava flow. With the exception of interior crater Ptolemaeus A, binoculars will see it as very smooth. Telescopes, however, can reveal faint mottling in the surface of the crater’s interior, along with a single elongated craterlet to the northeast. Despite its apparent uniformity, close inspection has revealed as many as 195 interior craterlets within Ptolemaeus! Look for a variety of interior ridges and shallow depressions.

With the Moon low to the southwest, we have a chance to go northeast to Cepheus for a new study – NGC 7160 (Right Ascension: 21 : 53.7 (hours : minutes) Declination: +62 : 36). At magnitude 6.1, this small open cluster is easily identified in scopes and may be seen as a faint starfield in binoculars. You’ll find it about a finger-width north of Nu Cephei.

Tuesday, August 28 – In 1789 on this day, Sir William Herschel discovered Saturn’s moon Enceladus.

On the lunar surface tonight, we’ll start by following the southward descent of large crater rings Ptolemaeus, Alphonsus, and Arzachel to a smaller, bright one southwest named Thebit. We’re going to have a look at Hell…

Just west of Thebit and its prominent A crater to the northwest, you see the Straight Wall – Rupes Recta – appearing as a thin, white line. Continue south until you see large, eroded crater Deslandres. On its western shore, is a bright ring that marks the boundary of Hell. While this might seem like an unusual name for a crater, it was named for an astronomer – and clergyman!

Once you’ve been to Hell, let’s go to the heavens for NGC 7235 (Right Ascension: 22 : 12.6 – Declination: +57 : 17). Locate the star crowded area of Epsilon Cephei which will also include this 7.7 magnitude open cluster in the same low power field. Give it a try. Look for a small, rectangular assortment of 10th magnitude and fainter stars, including a beautiful ruby red, west-northwest of Epsilon.

Wednesday, August 29 – Due south of mighty Copernicus on the eastern edge of Mare Cognitum, you will see a ruined pair of flattened craters. They are Bonpland and Parry – with Frau Mauro just above them. The smallest and brightest of these ancient twins is the eastern Parry. Have a look at its south wall where a huge section is entirely lost. It was near this location that Ranger 7 ended its successful flight in 1964. Just south of Parry is another example of a well-worn Class V crater. See if you can distinguish the ruins of Guericke. Not much is left save for a slight U-shape to its battered walls. These are some of the oldest visible features on the Moon!

If you’d like to head for something very young, have a look at 6.8 magnitude open cluster NGC 6811 (Right Ascension: 19 : 37.3 – Declination: +46 : 23) in Cygnus. This mid-sized, unusually dense open cluster is found less than finger-width north-northwest of Delta – the westernmost star of the Northern Cross. Like most open clusters, the age of NGC 6811 is measured in millions, rather than billions, of years. Visible in binoculars on most nights, telescopes should show a half dozen or so broadly-spaced resolvable stars overlaying a fainter field. Be sure to return again on a moonless night, and have another look a disparate double Delta!

Thursday, August 30 – Today celebrates the Yohkoh Mission, launched in 1991. It was a joint effort of both Japan and the United States to monitor solar flares and the corona. While its initial mission was quite successful, on December 14, 2001 the signal was lost during a total eclipse. Unable to reposition the satellite back towards the Sun, the batteries discharged and Yohkoh became inoperable.

While the graceful Gassendi will try to steal the lunar show tonight, let’s have a go at Foucault instead. To find it, head north to Sinus Iridum and locate Bianchini in the Juras Mountains. Just northeast, and near the shore of south-eastern Mare Frigoris, look for a bright little ring.

Physicist Jean Foucault played an instrumental role in the creation of today’s parabolic mirrors. His “Foucault knife edge test” made it possible for opticians to test mirror curves for optical excellence during the final phases of shaping before metallization. Thanks to Foucault’s insight, we can turn our telescopes on such difficult double stars as Beta Delphini and resolve its 0.6 arc-second distant 5.0 magnitude companion. A challenge for smaller scopes is MU Cygni. This 4.5 and 6.0 magnitude pair should be resolvable in any scope that passed Foucault’s test!

Tonight let’s view a double star, Eta Lyra. Just on the edge of unaided visibility, you will find it around three finger-widths due east of Vega. This wide, disparate pair of 4.5 and 8.0 magnitude stars should be resolvable in just about any scope, but is beyond the reach of binoculars.

Friday, August 31 – Tonight we will begin entering the stream of the Andromedid meteor shower, which peaks off and on for the next couple of months. For those of you in the northern hemisphere, look for the lazy “W” of Cassiopeia to the northeast. This is the radiant – or relative point of origin – for this meteor stream. At times, this shower has been known to be spectacular, but let’s stick with an accepted fall rate of around 20 per hour. These are the offspring of Beila’s Comet, one that split apart leaving radically different streams – much like 73/P Schwassman-Wachmann did last year. These meteors have a reputation for red fireballs with spectacular trains, so watch for them in the weeks ahead.

It’s Blue Moon! That doesn’t mean the Moon is going to be colored any differently – it just means it’s the second full Moon within a month.

Think having all this Moon around is the pits? Then let’s venture to Zeta Sagittarii and have a look at Ascella – “The Armpit of the Centaur.” While you’ll find Zeta easily as the southern star in the handle of the teapot formation, what you won’t find is an easy double. With almost identical magnitudes, Ascella is one of the most difficult of all binaries. Discovered by W. C. Winlock in 1867, the components of this pair orbit each other very quickly – in just a little more than 21 years. While they are about 140 light-years away, this gravitationally bound pair waltz no further apart than our own Sun and Uranus!

Too difficult? Then have a look at Nu Sagittarii – Ain al Rami, or the “Eye of the Archer.” It’s one of the earliest known double stars and was recorded by Ptolemy. While Nu 1 and Nu 2 are actually not physically related to one another, they are an easy split in binoculars. Eastern Nu 2 is a K type spectral giant that is around 270 light-years from our solar system. But take a very close look at the western Nu 1 – while it appears almost as bright, this one is 1850 light-years away! As a bonus, power up in the telescope, because this is one very tight triple star system!

Saturday, September 1 – On this day 1859, solar physicist Richard Carrington (who originally assigned sunspot rotation numbers) observed the first solar flare ever recorded. Naturally enough, an intense aurora followed the next day. 120 years later in 1979, Pioneer 11 made history as it flew by Saturn.

While the Moon essentially appears to be full throughout the night, take the time to compare the western and eastern limbs. To the west, you will see the smooth arc no longer displays high contrast features. To the east you should see a broken edge now in sunset. Watch in the days ahead as many of your favorite craters begin to reveal themselves in a “different light.”

Tonight let’s visit Alya. One of the fainter stars to receive a proper name, Theta Serpens Caput is located around a hand span due east of Beta Ophiuchi. Thankfully, resolving this wide, matched magnitude pair is easier than finding it. If you have high power, self-stabilizing binoculars, this one could be real fun!

Sunday, September 2 – It won’t be long until the Moon lights the skies, so let’s have a look at disparate double Kappa Pegasi. It’s the westernmost star of northern Pegasus and is around a hand span due south of Sadr – the central star of the Northern Cross. At magnitude 4.3, look for a faint companion leading the orange-yellow primary across the sky. This one could be tough for small scopes – so make a challenge of it!

Now let’s have a look at Beta and Gamma Lyrae – the lower two stars in the “Harp.” Beta is actually a quick change variable dropping to less than half the brightness of Gamma every 12 days, but for a few days the two stars appear to be of near equal brightness. Beta is a very unusual eclipsing spectroscopic binary. Its unseen companion may be a “collapsar.”
Before you call it a night, head a finger-width north of Omicron Andromedae for 15 Lacertae. Just on the edge of unaided visibility, this carbon star is also a disparate double. The 5.2 magnitude variable primary will appear more red at its faintest, but its 11.0 magnitude companion is the faintest of all!

But don’t put the telescope away just yet. If you can locate the Moon, you can locate Uranus! Just take a look about 3 degrees away to lunar south to catch the slightly greenish orb of the outer planet.

Until next week, ask for the Moon… But keep on reaching for the stars!

Ptolemaeus Crater Image Credit: Damian Peach