Meteor Showers in Oct, Nov, Dec 2016.
**The Geminids are the best at 120 meteors per hour, are on 14 Dec. *The Orionids (21 Oct) and the Leonids (17 Nov) both at 15 meteors per hour are middling. The Northern Taurids on 12 Nov at 5 meteors per hour aren’t as frequent but they produce many bright fireballs, and flashes on the Moon. However, the bright Moon will spoil much of the meteor showers this year. Meteor velocities can range from about 11 km/s (very slow) to 72 km/s (very fast). 40 km/s is roughly medium speed. (That’s still pretty fast. For comparison, the International space station orbits at 8km/s, and goes around the Earth in 90 minutes.) These meteors travel across the sky very swiftly, with “trains”. Look for a series of small explosions in the meteor trail as the rock breaks up. Some leave a luminous train of particles that last for a few seconds or even a minute. Colours can be yellow to brilliant green. You may hear a delayed supersonic rumble (5 minutes later) if a fireball comes close overhead and a chirp of descending pitch on a shortwave radio, from the meteors ion plasma.
*Fri 21 Oct: The ORIONIDs: Active: Oct 02–Nov 07 with maximum on Friday Oct 21; The zenith hourly rate (ZHR) is 15 meteors/hr; with a fast speed of 66 km/s, the remnants of Comet Halley. This year is likely a typical shower at 15 meteors per hour. This can vary from year to year, with a 12 year cycle of strong and weak peaks ranging from 14 to 31 meteors per hour; and another factor which can produce outbursts of 70 meteors/hr. The Moon will rise around midnight at its last quarter (65%-illuminated) which bright glow will drown out the fainter meteors. The meteors should radiate out from the North part of Orion the Hunter, by his club, on the Eastern horizon. Since the Moon is located quite close to the radiant at this time it will spoil all optical observations.
These meteors consist of falling ice pellets, dust and sand debris encountered as the Earth crosses the orbit of Halley’s Comet, coming in fast at 66 km per second. This debris moves parallel to itself along the orbit of the comet, thus from our Earth perspective it looks like they radiate out from a single point, the “radiant”. The Orionids all appear to radiate out from Orion, the streaks looking like huge bicycle spokes with the centre hub at Orion’s shoulder. They are visible coming from the Eastern horizon when Orion rises after midnight towards 1 to 6am. The half of the meteors that go below the horizon won’t be seen. You should be out of town where it’s dark to see them best. Don’t look towards the East, these trails will look short due to foreshortening. Instead look 90 degrees away, either straight overhead, or to the North, away from the Moon’s bright light.
Sat 12 Nov: The Northern TAURIDs: (Active: Oct 20 to Dec 10, max on 12 Nov). The zenith hourly rate (ZHR) is just 5 meteors/hour; velocity a slow 29km/s. The Earth passes through a debris stream left by Comet Encke, source of the Taurid Meteor Shower. Taurid meteors tend to be larger than average: they are bright, with many fireballs. They also penetrate deeper into the Earth’s atmosphere than other meteors. For example, Orionids typically burn up at altitudes of 93 km, but the Taurids make it down to 68 km. Some get even lower — meteor cameras have tracked 1-inch Northern Taurid meteors down to 58 km.
Moon Impacts: Because the Taurid Meteors can be 1 inch bullets of ice moving at 29 km/s (which is a hypersonic mach 88), they produce bright flashes of light when they strike the Moon. Taurid lunar impacts are visible with the college’s 10″ or 11” Schmidt-Cassegrain telescopes as small flickers of light, in dark regions. However, since the moon is 94% illuminated on Nov 12, there’s not much dark area to look into. But sometimes you can see brighter flashes in the illuminated area as well. Some telescopes are fitted with video cameras and count how many meteors hit the Moon overall. One impact imaged on Sep 2013 was so hot it glowed white hot for 8 seconds–it was estimated to be a 40kg rock.
*Thu 17 Nov: The LEONIDs Active: Nov 06–Nov 30 Nov 17; Maximum: Thu Nov 17; ZHR = 15 meteors/hr; V = 71 km/s. These arrive just three days after the full Moon, which will make it hard to see them. There are a lot of fast green meteors in the Leonids.
Mon 28 Nov: The November Orionids. Active: November 14–December 6; Maximum: Monday Nov 28; ZHR = 3 meteors/hr; V = 44 km/s
**Wed 14 Dec: The GEMINIDS; active Dec 04–Dec 17; Maximum: Dec 14; ZHR = 120 meteors/hr; V= 35 km/s.
The best and most reliable meteor shower of the year are the Geminids at 120 meteors per hour on Wednesday, December 14. Except we have the Full Moon on the same night to spoil them. The Geminid meteors are debris from an extinct comet (called 3200 Phaethon) coming in at 35 km/second. (That’s a medium speed for a meteor. Other meteor shower velocities range from 11 to 72 km/s.) The Geminids come in various colours–65% being white, 26% yellow, and the remaining 9% blue, red and green. The meteors are the sand, dust and gravel remains of an Apollo asteroid (3200 Phaethon), coming in at medium speeds of 35km/second.
Colourful meteor here taken by Robert Ede in Invermere, against the Milky Way to the South. Note the colour in the trail starts green and turns red.
Fireball Colours: Green can be caused by copper or magnesium metal burning. Other colours seen are yellow, orange and red. Iron burns yellow (eg. steel wool), silicates burn red and sodium burns orange.
Ionization trails: Sometimes the wakes behind them can be ionized oxygen emitting green light. That occurs at higher altitudes where the air pressure is low. The higher collision energies make oxygen produce a greenish glow, nitrogen emits blue and red, at the lower energies a dim red. Just like the colours in the Northern Lights. So, fast meteors would have more energy and produce more greens and blues, slow meteors would have lower energy and produce reds.
Which direction is best to look? Where it’s darkest. As you can see in these composite photos from last year, the fireballs scatter all over the sky, radiating out from Gemini to the East. But when you watch the area around Gemini, the streaks there are shorter and slower moving. These fisheye photos show the whole sky as a circle: North is up, South down, East to the left, and West to right.
All the brighter Geminid Meteors during the night of 14 Dec 2014. The photos were taken with the College of the Rockies meteor cam in Cranbrook, BC.
It is thought the Geminids originated from an asteroid named 3200 Phaethon, discovered in 1983. It may be a small 5km fragment from the 544km main belt asteroid Pallas