Our Guide to the 2016 Geminid Meteors: Watching a Good Shower on a Bad Year

2015 Geminids

One of the best yearly meteor showers contends with the nearly Full Moon this year, but don’t despair; you may yet catch the Geminids.

The Geminid meteor shower peaks next week on the evening of Tuesday night into Wednesday morning, December 13th/14th. The Geminids are always worth keeping an eye on in early through mid-December. As an added bonus, the radiant also clears the northeastern horizon in the late evening as seen from mid-northern latitudes. The Geminids are therefore also exceptional among meteor showers for displaying early evening activity.

Stellarium
The Geminid radiant, looking east around 11 PM local on the evening of December 13th. Note the nearby Moon in the same constellation. Image credit: Stellarium.

First, though, here is the low down of the specifics for the 2016 Geminids: the Geminid meteors are expected to peak on December 13th/14th at midnight Universal Time (UT), favoring Western Europe. The shower is active for a two week period from December 4th to December 17th and can vary with a Zenithal Hourly Rate (ZHR) of 50 to 80 meteors per hour, to short outbursts briefly topping 200 per hour. In 2016, the Geminids are expected to produce a maximum ideal ZHR of 120 meteors per hour. The radiant of the Geminids is located at right ascension 7 hours 48 minutes, declination 32 degrees north at the time of the peak, in the constellation of Gemini.

The Moon is a 98% illuminated waning gibbous just 20 degrees from the radiant at the peak of the Geminids, making 2016 an unfavorable year for this shower. In previous years, the Geminids produced short outbursts topping 200 per hour, as last occurred in 2014.

The Geminid meteors strike the Earth at a relatively slow velocity of 35 kilometers per second, and produce many fireballs with an r vaule of 2.6. The source of the Geminid meteors is actually an asteroid: 3200 Phaethon

Orbitron
The orientation of the radiant versus the Sun, Moon and Earth’s shadow just past midnight Universal Time on the evening of December 13th/14th. (Created using Orbitron).

A moderate shower in the late 20th century, the Geminids have increased in intensity during the opening decade and a half of the 21st century, surpassing the Perseids for the title of the top annual meteor shower.

Image credit: NASA JPL.
The orbit of 3200 Phaethon. Image credit: NASA JPL.

The Geminid shower seems to have breached the background sporadic rate around the mid-19th century. Astronomers A.C. Twining and R.P. Greg observing from either side of the pond in the United States and the United Kingdom both first independently noted the shower in 1862.

Orbiting the Sun once every 524 days, 3200 Phaethon wasn’t identified as the source of the Geminids until 1983. The asteroid is still a bit of a mystery; reaching perihelion just 0.14 astronomical units (AU) from the Sun, (interior to Mercury’s orbit) 3200 Phaethon is routinely baked by the Sun. Is it an inactive comet nucleus? Or a ‘rock comet’ in a transitional state?

Observing meteors is as simple as setting out in a lawn chair, laying back and watching with nothing more technical than a good ole’ Mk-1 pair of human eyeballs. Our advice for 2016 is to start watching early, like say this weekend, before the Moon reaches Full on Wednesday, December 14th. This will enable you to watch for the Geminids after morning moonset under dark skies pre-peak, and before moonrise on evenings post-peak.

Two other minor showers are also active next week: the Coma Bernicids peaking on December 15th, and the Leo Minorids peaking on December 19th. If you can trace a suspect meteor back to the vicinity of the Gemini ‘twin’ stars of Castor and Pollux, then you’ve most likely spied a Geminid and not an impostor.

And speaking of the Moon, next week’s Full Moon is not only known as the Full Cold Moon (For obvious reasons) from Algonquin native American lore, but is also the closest Full Moon to the December 21st, northward solstice. This means that next week’s Full Moon rides highest in the sky for 2016, passing straight overhead for locales sited along latitude 17 degrees north, including Guatemala City and Mumbai, India.

A 2015 Geminid over Sariska Palace in Rajastan, Pakistan (ck). Image credit and copyright: Abhinav Singhai.
A 2015 Geminid over Sariska Palace in Rajastan, India. Image credit and copyright: Abhinav Singhai.

Photographing the Geminids is also as simple as setting a camera on a tripod and taking wide-field exposures of the sky. We like to use an intervalometer to take automated sequences about 30 seconds to 3 minutes in length. Said Full Moon will most likely necessitate shorter exposures in 2016. Keep a fresh set of backup batteries handy in a warm pocket, as the cold December night will drain camera batteries in a pinch.

Looking to contribute some meaningful scientific observations? Report those meteor counts to the International Meteor Organization.

Our humble meteor imaging rig. Credit: Dave Dickinson.
Our humble meteor imaging rig. Credit: Dave Dickinson.

And although the Geminids might be a bust in 2016, another moderate shower, the Ursids has much better prospects right around the solstice… more on that next week!

Viewing Guide to the 2015 Geminid Meteor Shower

A brilliant Geminid flashes below Sirius and Orion over Mount Balang in China. Credit: NASA/Alvin Wu

2015 looks like a fantastic year for the Geminids. With the Moon just 3 days past new and setting at the end of evening twilight, conditions couldn’t be more ideal. Provided the weather cooperates! But even there we get a break. With a maximum of 120 meteors per hour, the shower is expected to peak around 18:00 UT (1 p.m. EST, 10 a.m. PST) December 14th, making for two nights of approximately equal activity: Sunday night Dec. 13-14 and Monday night Dec. 14-15.  Continue reading “Viewing Guide to the 2015 Geminid Meteor Shower”

The Curious History of the Geminid Meteors

UPDATE: Tune in this Sunday as the good folks over at the Virtual Telescope Project feature a live webcast covering the Geminid meteor shower this Sunday on December 14th at 2:00 UT.

This weekend presents a good reason to brave the cold, as the Geminid meteor shower peaks on the morning of Sunday, December 14th. The Geminids are dependable, with a broad peak spanning several days, and would be as well known as their summer cousins the Perseids, were it not for the fact that they transpire in the dead of northern hemisphere winter.

But do not despair. While some meteor showers are so ephemeral as to be considered all but mythical in the minds of most meteor shower observers, the Geminids always deliver. We most recently caught a memorable display of the Geminids in 2012 from a dark sky locale in western North Carolina. Several meteors per minute pierced the Appalachian night, offering up one of the most memorable displays by this or any meteor shower in recent years.

The Geminids are worth courting frostbite for, that’s for sure. But there’s a curious history behind this shower and our understanding of meteor showers in general, one that demonstrates the refusal of some bodies in our solar system to “act right” and fit into neat scientific paradigms.

UK Meteor Observation Network
A composite of the 2013 Geminids. Credit: the UK Meteor Observation Network

It wasn’t all that long ago that meteor showers — let alone meteorites — were not considered to be astronomical in origin at all. Indeed, the term meteor and meteorology have the same Greek root meaning “of the sky,” suggesting ideas of an atmospheric origin. Lightning, hail, meteors, you can kind of see how they got there.

In fact, you could actually face ridicule for suggesting that meteors had an extraterrestrial source back in the day. President Thomas Jefferson was said to have done just that concerning an opinion espoused by Benjamin Silliman of a December 14th, 1807, meteorite fall in Connecticut, leading to the apocryphal and politically-tinged response attributed to the president that, “I would more easily believe that two Yankee professors would lie, than that stones would fall from heaven.”

Indeed, no sooner than The French Academy of Sciences considered the matter settled earlier in the same decade, then a famous meteorite fall occurred in Normandy on April 26th, 1803,… right on their doorstep. The universe, it seemed, was thumbing its nose at scientific enlightenment.

A fine Geminid
A fine 2004 Geminid as imaged by Frankie Lucena.

Things really heated up with the spectacular display known as the Leonid meteor storm in 1833. On that November morning, stars seemed to fall like snowflakes from the sky. You can imagine the sight, as the Earth plowed headlong into the meteor stream. The visual effect of such a storm looks like the starship Enterprise plunging ahead at warp speed with stars streaming by, as if imploring humanity to get hip to the fact that meteor showers and their radiants are indeed a reality.

Still, a key problem persisted that gave ammunition to the naysayers: no new “space rocks” were found littering the ground at sunrise after a meteor shower. We now know that this is because meteor showers hail from wispy cometary debris left along intersections of the Earth’s orbit.  Meteorite Man Geoff Notkin once mentioned to us that no meteorite fall has ever been linked to a meteor shower, though he does get lots of calls around Geminid season.

The name of the game in the 19th century soon became identifying new meteor showers. Streams evolve over time as they interact with planets (mostly Jupiter), and the 19th century played host to some epic meteor storms such as the Andromedids that have since been reduced to a trickle.

The Geminids are, however, the black sheep of the periodic meteor shower family. The shower was first noticed by US and UK observers in 1862, and by the 1870s astronomers realized that a new minor shower with a Zenithal Hourly Rate (ZHR) hovering around 15 was occurring near the middle of December from the constellation Gemini.

NASA
A possible early 2014 Geminid and the near Full Moon as seen by NASA’s All Sky Fireball Network.

The source of the Geminids, however, was to remain a mystery right up until the late 20th century.

In the late 1940s, astronomer Fred Whipple completed the Harvard Meteor Project, which utilized a photographic survey that piqued the interest of astronomers worldwide: debris in the Geminid stream appeared to have an orbital period of just 1.65 years, coupled with a high orbital inclination. Modeling suggested that the parent body was most likely a short period comet, and that the stream had undergone repeated perturbations courtesy of Earth and Jupiter.

In 1983, the culprit was found, only to result in a deeper mystery. The Infrared Astronomical Satellite (IRAS) discovered an asteroid fitting the bill crossing the constellation Draco. Backup observations from the Palomar observatory the next evening cinched the discovery, and today, we recognize the source of the Geminids as not a comet — as is the case with every other major meteor shower — but asteroid 3200 Phaethon, a 5 kilometre diameter rock in a 524 day orbit.

3200 Phaethon
Asteroid 3200 Phaethon (arrowed) imaged by Marco Langbroek from the Winer Observatory in Sonita, Arizona. Credit: Wikimedia Commons.

So why doesn’t this asteroid behave like one? Is 3200 Phaethon a rogue comet that has long since settled down for the quiet space rock life? Obviously, 3200 Phaethon has lots of material shedding off from its surface, as evidenced by the higher than normal ratio of fireballs seen during the Geminid meteors. 3200 Phaethon also passes 0.14 AUs from the Sun — 47% closer than Mercury — and has the closest perihelion of any known asteroid to the Sun, which bakes the asteroid periodically with every close pass.

One thing is for certain: activity linked to the Geminid meteor stream is increasing. The Geminids actually surpassed the Perseids in terms of dependability and output since the 1960s, and have produced an annual peak ZHR of well over 100 in recent years. In 2014, expect a ZHR approaching 130 per hour as seen from a good dark sky site just after midnight local on the morning of December 14th as the radiant rides high in the sky. Remember, this shower has a broad peak, and it’s worth starting your vigil on Saturday or even Friday morning. The Geminid radiant also has a steep enough declination that local activity can start before midnight… also exceptional among meteor showers. This year, the 52% illuminated Moon rises around midnight local on the morning of December 14th.

Credit: Stellarium
The Geminid radiant looking to the northeast at 11PM local. Note the radiant of the December 22nd Ursids is also nearby. Credit: Stellarium.

And there’s another reason to keep an eye on the 2014 Geminids. 3200 Phaethon passed 0.12 AU (18 million kilometers) from Earth on December 10th, 2007, which boosted displays in the years after. And just three years from now, the asteroid will pass even closer on December 10th, 2017, at just 0.07 AUs (10.3 million kilometers) from Earth…

Are we due for some enhanced activity from the Geminids in the coming years?

All good reasons to bundle up and watch for the “Tears of the Twins” this coming weekend, and wonder at the bizzaro nature of the shower’s progenitor.

 

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.

Asteroid Vs. Comet: What The Heck Is 3200 Phaethon?

Sometimes, putting things into categories difficult. Witness how many members of the general public are still unhappy that Pluto was reclassified as a dwarf planet, a decision made by the International Astronomical Union more than seven years ago.

And now we have 3200 Phaethon, an asteroid that is actually behaving like a comet. Scientists found dust that is streaming from this space rock as it gets close to the sun — similarly to how ices melt and form a tail as comets zoom by our closest stellar neighbor.

Phaethon’s orbit puts it in the same originating region as other asteroids (between Mars and Jupiter), but its dust stream is much closer to actions performed by a comet — an object that typically comes from an icy region way beyond Neptune. So far, therefore, the research team is calling Phaethon a “rock comet.” And after first proposing a theory a few years ago, they now have observations as to what may be going on.

Phaethon is not only an asteroid, but also a source of a prominent meteor shower called the Geminids. This shower happens every year around December when the Earth plows into the cloud of debris that Phaethon leaves in its wake. Astronomers have known about the Geminids’ source for a generation, but for decades could not catch the asteroid in the act of shedding its stuff.

That finally came with images of NASA’s twin sun-gazing Solar TErrestrial RElations Observatory (STEREO) spacecraft that were taken between 2009 and 2012. The researchers saw a “comet-like tail” extending from the 3.1-mile (five kilometer) asteroid. “The tail gives incontrovertible evidence that Phaethon ejects dust,” stated David Jewitt, an astronomer at the University of California, Los Angeles who led the research. “That still leaves the question: why?”

Time lapse-photo showing geminids over Pendleton, OR. Credit: Thomas W. Earle
Time lapse-photo showing geminids over Pendleton, OR. Credit: Thomas W. Earle

The answer lies in just how close Phaethon whizzes past the sun. At perihelion, its closest approach to the sun, it only appears eight degrees (16 solar diameters) away from the sun in Earth’s sky. This close distance makes it all but impossible to study the asteroid without special equipment, which is why STEREO came in so handy.

When Phaethon reaches its closest approach of 0.14 Earth-sun distances, surface temperatures rise above an estimated 1,300 degrees Fahrenheit (700 degrees Celsius). It’ s way too hot for ice, as what happens with a comet. In fact, it’s probably hot enough to make the rocks crack and break apart. The researchers publicly hypothesized this was happening at least as far back as 2010, but this finding provided more evidence to support that theory.

“The team believes that thermal fracture and desiccation fracture (formed like mud cracks in a dry lake bed) may be launching small dust particles that are then picked up by sunlight and pushed into the tail,” a statement from the research team read.

“While this is the first time that thermal disintegration has been found to play an important role in the solar system,” they added, “astronomers have already detected unexpected amounts of hot dust around some nearby stars that might have been similarly produced.”

The results were presented at the European Planetary Science Congress on Tuesday. By the way, STEREO also caught Mercury behaving somewhat like a comet in results released in 2010, although that find was related to the planet’s escaping sodium atmosphere.

Read more about the research in the June 26 issue of Astrophysical Letters. A preprint version is also available on Arxiv.

Source: European Planetary Science Congress