Parker Solar Probe Makes a Surprising Discovery About the Source of the Geminid Meteor Shower

The Geminid meteor shower in the Northern Hemisphere. Credit: Asim Patel

If you’ve ever seen a meteor shower, you know it can be an amazing sight. You watch the skies as every few moments there’s a streak of light. Sometimes bright and in your field of vision. Sometimes starting just out of the corner of your eye. Although a meteor can occur at any time, they tend to appear at certain times of the year, such as the Perseids of August, or the Orionids of October.

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The Geminids Will be Peaking on December 14th. They’re Usually the Most Active Meteor Shower Every Year

Meteor showers are a great way to share a love of astronomy with those who might not be as familiar with it. Almost everyone loves watching streaks of light flash across the sky, but usually, it’s so intermittent that it can be frustrating to watch. That’s not the case for the next few weeks, though, as the annual Geminid meteor shower is underway until December 24th.

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The Gemini Constellation

The two bright stars Castor and Pollux each mark a starry eye of a Gemini Twin. If you have binoculars and a dark sky, be sure to check out Gemini’s beautiful star cluster, Messier 35, or M35, in western Gemini near the Taurus border. See it, at the foot of Castor? Image via AugPi/ Wikimedia Commons.

Welcome to another edition of Constellation Friday! Today, in honor of the late and great Tammy Plotner, we take a look at “the Twins” – the Gemini constellation. Enjoy!

In the 2nd century CE, Greek-Egyptian astronomer Claudius Ptolemaeus (aka. Ptolemy) compiled a list of the then-known 48 constellations, the sum of thousands of years’ worth of charting the heavens. This treatise, known as the Almagest, would be used by medieval European and Islamic scholars for over a thousand years to come, effectively making it the astrological and astronomical canon until the early Modern Age.

One of the original 48 is Gemini, a constellation located on the ecliptic plane between Taurus (to the west) and Cancer (to the east). Its brightest stars are Castor and Pollux, which are easy to spot and represent the “Twins,” hence the nickname. Gemini is bordered by the constellations of Lynx, Auriga, Taurus, Orion, Monoceros, Canis Minor, and Cancer. It has since become part of the 88 modern constellations recognized by the International Astronomical Union.

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Brrrr: Bundle Up For the 2021 Geminid Meteors

One of the best annual meteor showers of the year, the Geminids top off 2021.

Ready to brave the cold? If you’re like us, you haven’t wasted an early clear sky morning to get out and see Comet C/2021 A1 Leonard before it heads southward. The coming days offer another early AM celestial sight: the Geminid meteors. To be sure, 2021 sees the Geminid meteors transpire under somewhat challenging conditions. But fear not: with a little planning and patience, you too can witness the ‘Tears of the Twins.’

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December Meteor Squalls: Prospects for the 2019 Geminids and Ursids

2019 Geminids
A composite of several exposures to stack images of five Geminid meteors into a wide view of the winter sky with Comet Wirtanen at upper right in Taurus, taken on December 12, 2018. The meteors are shooting away from the radiant point in Gemini near the bluish-white star Castor at left. The Milky Way runs vertically through the frame from Auriga at top to past Orion at bottom. All the images for the base sky layer and the meteors were shot as part of the same sequence and framing, with a 24mm lens and Nikon D750 on a Star Adventurer tracker. The camera is unmodified so the red nebulosity in this part of the sky appears rather pale. Capella and the Pleiades are at top, Orion is at bottom, Taurus is at centre, while Gemini and the radiant point of the shower is at lower left. The Taurus Dark Clouds complex is at upper centre. All exposures were 30 seconds at f/2 and ISO 1600. I started the sequence with the camera framing this area of the sky when it was just rising in the east in the moonlight then followed it for 4 hours until clouds moved in. So all the images align, but out of 477 frames shot only these 5 had Geminid meteors. Images layered and stacked in Photoshop. Image Credit and Copyright: Alan Dyer/

December means chillier climes for northern hemisphere residents, a time to huddle inside near the campfire, both real and cyber. I’ve always thought this was a shame, as the cold crisp nights of winter also offer up sharp, clear skies. Over the past decade or so, December gives observers another reason to brave the cold: the Geminids.

Continue reading “December Meteor Squalls: Prospects for the 2019 Geminids and Ursids”

Get Ready for the 2018 Geminid Meteors

2018 Geminids
A timelapse of the 2017 Geminids, taken from the Chiricahua Mountains in southern Arizona. Image credit and copyright: Alan Dyer/

When it comes to meteor showers, the calendar year always seems to save the best for last. We’re referring to the Geminid meteor shower, one of the sure fire bets for dependable meteor showers. In fact, in recent years, the Geminids have been upstaging that other yearly favorite: the August Perseids. If the Geminids did not occur in the chilly (for the northern hemisphere) month of December, they’d most likely get a better rap. Continue reading “Get Ready for the 2018 Geminid Meteors”

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

2015 Geminids
The 2015 Geminids over the LAMOST observatory in China. Image credit and copyright: SteedJoy.

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.

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

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
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”

Don’t Miss the Geminids this Weekend, Best Meteor Shower of the Year

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

Wouldn’t it be nice if a meteor shower peaked on a weekend instead of 3 a.m. Monday morning? Maybe even showed good activity in the evening hours, so we could get our fill and still get to bed at a decent hour. Wait a minute – this year’s Geminids will do exactly that!

Before moonrise this Saturday night December 13th, the Geminids should put on a sweet display. The radiant of the shower lies near the bright pair of stars, Castor and Pollux. Source: Stellarium
Before moonrise this Saturday night December 13th, the Geminids should put on a sweet display. The radiant of the shower lies near the bright pair of stars, Castor and Pollux. Source: Stellarium

What’s more, since the return of this rich and reliable annual meteor shower occurs around 6 a.m. (CST) on Sunday December 14th, both Saturday and Sunday nights will be equally good for meteor watching. After the Perseids took a battering from the Moon last August, the Geminids will provide the best meteor display of 2014.  They do anyway! The shower’s been strengthening in recent years and now surpasses every major shower of the year.

The official literature touts a rate of 120 meteors per hour visible from a dark sky site, but I’ve found 60-80 per hour a more realistic expectation. Either way, what’s to complain?

The third quarter Moon rises around midnight Saturday and 1 a.m. on Monday morning. Normally, moonlight would be cause for concern, but unlike many meteor showers the Geminids put on a decent show before midnight. The radiant, the location in the sky from which the meteors will appear to stream, will be well up in the east by 9:30 p.m. local time. That’s a good 2-3 hours of meteor awesomeness before moonrise.

The author tries his best to enjoys this year's moon-drenched Perseids from the "astro recliner". Credit: Bob King
The author takes in this year’s moon-drenched Perseids in comfort.

Shower watching is a total blast because it’s so simple. Your only task is to dress warmly and get comfortable in a reclining chair aware from the unholy glare of unshielded lighting. The rest is looking up. Geminid meteors will flash anywhere in the sky, so picking a direction to watch the shower isn’t critical. I usually face east or southeast for the bonus view of Orion lumbering up from the horizon.

Bring your camera, too. I use a moderately wide angle lens (24-35mm) at f/2.8 (widest setting), set my ISO to  800 or 1600 and make 30-second exposures. The more photos you take, the better chance of capturing a meteor. You can also automate the process by hooking up a relatively inexpensive intervalometer  to your camera and have it take the pictures for you.

As you ease back and let the night pass, you’ll see other meteors unrelated to the shower, too. Called sporadics, they trickle in at the rate of  2-5 an hour. You can always tell a Geminid from an interloper because its path traces back to the radiant. Sporadics drop down from any direction.

A Geminid fireball brighter than Venus streaks across the sky above New Mexico on Dec. 14, 2011. It was captured by an all-sky camera. Before disintegrating in the atmosphere the meteoroid was about 1/2 inch across. Credit: Marshall Space Flight Center, Meteoroid Environments Office, Bill Cooke
Captured by an all-sky camera, a Geminid fireball brighter than Venus streaks across the sky above New Mexico on Dec. 14, 2011. Before disintegrating in the atmosphere the meteoroid was about 1/2 inch across. Credit: Marshall Space Flight Center, Meteoroid Environments Office, Bill Cooke

Geminid meteors immolate in Earth’s atmosphere at a moderate speed compared to some showers – 22 miles per second (35 km/sec) – and often flare brightly. Green, red, blue, white and yellow colors have been recorded, making the shower one of the more colorful. Most interesting, the meteoroid stream appears to be sorted according to size with faint, telescopic meteors maxing out a day before the naked eye peak. Larger particles continue to produce unusually bright meteors up to a few days after maximum.

Most meteor showers are the offspring of comets. Dust liberated from vaporizing ice gets pushed back by the pressure of sunlight to form a tail and fans out over the comet’s orbital path. When Earth’s orbit intersects a ribbon of this debris, sand and gravel-sized bits of rock crash into our atmosphere at high speed and burn up in multiple flashes of meteoric light.

Phaethon sprouts a tail when close to the Sun seen in this image taken by NASA's STEREO Sun-observing spacecraft in 2012. Credit: Credit: Jewitt, Li, Agarwal /NASA/STEREO
Phaethon sprouts a tail (points southeast or to lower left) when close to the Sun in this image taken by NASA’s STEREO Sun-observing spacecraft in 2012. Credit: Credit: Jewitt, Li, Agarwal /NASA/STEREO

But the Geminids are a peculiar lot. Every year in mid-December, Earth crosses not a comet’s path but that of 3200 Phaethon (FAY-eh-thon), a 3.2 mile diameter (5.1 km)  asteroid. Phaethon’s elongated orbit brings it scorchingly close (13 million miles) to the Sun every 1.4 years. Normally a quiet, well-behaved asteroid, Phaethon brightened by a factor of two and was caught spewing jets of dust when nearest the Sun in 2009, 2010 and 2012. Apparently the intense heat solar heating either fractured the surface or heated rocks to the point of desiccation, creating enough dust to form temporary tails like a comet.

While it looks like an asteroid most of the time, Phaethon may really be a comet that’s still occasionally active. Periodic eruptions provide the fuel for the annual December show.

Most of us will head out Saturday or Sunday night and take in the shower for pure enjoyment, but if you’d like to share your observations and contribute a bit of knowledge to our understanding of the Geminids, consider reporting your meteor sightings to the International Meteor Organization. Here’s the link to get started.

And this just in … Italian astronomer Gianluca Masi will webcast the shower starting at 8 p.m. CST December 13th (2 a.m. UT Dec. 14) on his Virtual Telescope Project site.