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Wherever night skies are dark enough – especially far from the glow of city lights – skywatchers might see shooting stars flit through the sky. Every so often Earth passes through clouds of comet debris that cause more lively displays of shooting stars called meteor showers. The Geminid meteor shower occurs each December and peaks on the mornings of Dec. 14 and 15, followed on the winter solstice by the less active Ursid meteor shower.
The Geminids – so named because they appear to radiate from the constellation Gemini (which is actually about 52 light years away) – are famously active, with some estimates for this year’s shower of up to 120 meteors per hour in very dark skies. That means even Evanstonians have a chance of seeing a few. The full moon’s glow could dim the display, according to Bruce McClure of earthsky.org, but he says some of the brighter Geminids might make an appearance all the same.
Most meteor showers are caused by comets, dirty cosmic ice balls that leave trails of debris in space. Those bits of debris – some no larger than grains of sand – are called meteoroids. When meteoroids blast through Earth’s atmosphere, they cut a white streak in the sky as they burn up, leaving what we see as meteors or shooting stars. (Meteorites are meteoroids that survive the atmospheric impact and land on Earth.)
Geminids are unique in that their source is an asteroid – or, to use NASA’s term, a “weird rocky object” called 3200 Phaethon. Asteroids don’t usually carry lots of debris with them, as comets do, and scientists are still trying to figure out how 3200 Phaethon – also known as a rock comet – creates enough celestial rubble to cause one of the busiest meteor showers each year. Nevertheless, 3200 Phaethon orbits merrily around the solar system, flinging loads of meteors through our atmosphere every December and promising dozens of wishable shooting stars.
The Geminid radiant – the point in Gemini from which meteors appear to originate – is well up in the sky by 9 p.m., according to skyandtelescope.com, but peak viewing time will be around 2 a.m., when most people want to be tucked between warm flannel sheets dreaming of sugarplums. To those willing to brave a cold and sleepless night in the hopes of wishing on a star, dress very warmly and maybe even bring a thermos of something hot to drink. Sit on a reclining chair or lie on a thick blanket, to avoid a neck ache from looking up for extended periods. And remember that it can take up to 20 minutes to adjust to the darkness.
To find Gemini, first look south to locate Orion the Huntsman – that impressively huge and recognizable winter constellation, with his shield and signature three star belt. Look northeast of Orion to see the “twins” that make up Gemini, with its two bright stars Castor and Pollux. Geminids can be seen anywhere in the night sky, but will appear to stream away from Castor.
The trick to seeing meteors is to look at the dark spaces between the stars – not always easy because our eyes are drawn to all the twinkly things. Patiently scan the sky for slivers of light that slice the darkness and vanish like the final moments of a fireworks sparkle. (And remember to make a wish!) Meteors come and go in the blink of an eye, but seeing just one can seem pretty magical. When it gets too cold, or if those shooting stars are not flying out of Gemini at an eye-popping rate, it may be best to go inside, thaw out with a nip of hot chocolate, and listen to a shooting star instead: tinyurl.com/hear-a-shooting-star.
The American Meteor Society’s website lists several major and dozens of minor meteor showers that occur regularly throughout the year. Websites like spaceweather.com, earthsky.org and skyandtelescope.com also provide viewing details as meteor showers approach, including whether moonglow will spoil the fun. Following are a few major showers coming up in the next year, including some that reliably produce fireballs – brighter, longer meteors that are rare to see but always spectacular.
Ursids. This year’s winter solstice coincides with the Ursids, which appear to radiate from Ursa Minor, the constellation which contains the Little Dipper and Polaris, the North Star. Ursids are active from Dec. 17-23, peaking in the wee hours of Dec. 22 with rates of about 5-10 meteors per hour. They emanate from Comet Tuttle (8P/Tuttle).
Lyrids. Lyrids, which often produce fireballs, will be active from April 16-25, peaking overnight on April 22-23. Lyrids radiate from the constellation Lyris, which will be high in the sky at dawn, and its source is Comet Thatcher (C/1861 G1).
Perseids. If watching shooting stars on a warm summer’s night sounds appealing, then the Perseids are the show to catch. They are active from July 13 to Aug. 26, peaking around Aug. 12 with rates ranging from 50-75 meteors per hour. Perseids emanate from Comet Swift-Tuttle (109P/Swift-Tuttle), and appear to radiate from the constellation Perseus.
Orionids. Orionids emanate from debris left by the famously visible Comet Halley, whose next appearance above Earth won’t happen until 2061. They are active from Oct. 4 to Nov. 14, peaking overnight on Oct. 21-22. Orionids usually produce 20-25 meteors per hour, but occasionally reach higher frequencies similar to the Perseids.
Taurids. Taurids produce few visible meteors but the possibility of bright fireballs increases during this lengthy show. The shower is divided into two overlapping segments – Southern Taurids and Northern Taurids – which are active from September to December. They appear to radiate from the constellation Taurus, and emanate from Comet Encke (2P/Encke), whose pebble-sized debris can cause fireballs.
Leonids. Over the past 200 years, the Leonids have produced several intense meteor “storms” when the source of its meteors, Comet Tempel-Tuttle (55p/Tempel-Tuttle), traveled closest to the sun. The next such storm might happen in 2099, with heavy displays predicted for 2031 and 2064. In 2017, Leonids will be active from Nov. 5-30.
Geminids. Geminids will appear as usual in 2017 from Dec. 4-16, peaking around Dec. 13-14.