Halley’s Comet Tosses Out Tootsie Rolls This Weekend

The annual Orionid meteor reaches maximum on Sunday, Oct. 22nd in the pre-dawn hours. The meteors can appear appear anywhere in the sky but all radiate from a point in the constellation Orion. Map: Bob King, Source: Stellarium

Old Halley’s Comet won’t be around till 2061 but that won’t stop it from sending a few snappy meteors our way this weekend. The annual Orionid meteor shower peaks on Sunday morning, Oct. 22nd between the hours of 2 and 6 a.m. local time. You can expect to see about 25 meteors an hour shoot from Orion’s upraised club from dark skies. And the moon, right around new, will give no guff.

Halley’s Comet sports two tails – dust (left) and gas – during its last swing by Earth in 1985-86. Bits of dust and ice from the tail burn up as Orionids. Credit: William Liller/NASA

Meteor showers get their name from the constellation in which the meteors appear to originate or as they say in astro lingo, “radiate.” That’s why you don’t have any Halleyids or Swift-Tuttleids (Perseids) though nearly every major shower stems from a particular comet. On the many occasions that the world’s most famous comet has dropped by the inner solar system, heat from the sun has boiled frozen gases along with dust from its icy nucleus. They create a temporary atmosphere around the comet called a coma and two tails, one made of dust and the other gas.

Material streaming away from the comet gets deposited along into spreading streams of debris, some denser than others. Every early May (Eta Aquarid shower) and October, the Earth passes through Halley’s dusty bits and thousands of mini-me Halleys slam into our atmosphere at speeds of 148,000 mph (238,000 km/hour) and burn up as meteors, better known as shooting stars. Meteoroids, the small bits of debris that range from sand-size to chocolate chips, are fluffy and quickly disintegrate as they strike the air … but not before putting on a great show.

Orionids hail from Halley’s Comet. When Earth encounters the inbound and outbound legs of the comet’s orbit, we plow through the comet’s dust trail and experience meteor showers twice: once in May and the second time in late October. Perturbations by planets and the Sun have caused the particles to spread out into a ribbon centered on Halley’s orbit. Halley’s position is shown at perihelion in 1986 and in the current year, 2017. Not to scale.

The energy of the movement, called kinetic energy, is transferred to the surrounding air molecules, which become ionized (lose electrons). When the electrons settle back to their original positions, they emit light. The meteoroid gets agitated, too. Slammed by bazillions of air molecules, it heats up and vaporizes, producing light according to its composition: blue-white for magnesium and orange for sodium.

Orionids have a lot of zip and burn up quickly when they strike the air some 60 miles (96 km) above our heads. You’ll notice this when you’re out watching. Anytime between 2 and about 6 a.m. works. Then, the constellation Orion stands high in the southeastern sky, an ideal place for shower meteors to make their best appearance.

Don’t just fly out the door either. Try to be civilized about the event. Boil some tea or make a cup of coffee. Wear a warm coat against the autumn dew and roll out a sleeping bag for your weary bones. Oh, and don’t forget a pillow to tuck behind your head. Now you’re ready for meteor shower watching.

Orion and the sky brightest star, Sirius, are high in the southern sky just before the beginning of morning twilight. Shoot a line through the belt to find Sirius. Created with Stellarium

Showers are also a fun time to get to know the constellations better, since you’re basically staring into space, waiting for Halley to toss out tootsie-rolls. Orion’s three belt stars, shining at a slant in the south, can’t be missed. If you shoot an imaginary arrow through them to the south (lower left), you’ll arrive at the brightest star in the sky, the Dog Star, Sirius. Shooting an arrow up the other way will take you to Aldebaran, the brightest star in Taurus the bull. Aldebaran shines in the foreground of the V-shaped Hyades star cluster, a beautiful and symmetric grouping of stars. Keep going above the Hyades and you’ll shortly come to that familiar pile of buckshot called the Pleiades or Seven Sisters cluster.

An Orionid meteor slashes across the top of the frame directly above the constellation Orion on October 22, 2014. Details: 24mm lens, f/2.8, 30-seconds at ISO 1600. Credit: Bob King

Sporadic or random meteors will be out, too. To distinguish them from Orionids, just follow their trails backward — only Orionids will take you back to northern Orion. The shower has a broad peak, meaning if bad weather interferes, you can still see it a couple days before and after though with lower numbers, more like 10 meteors an hour. So find a place without yard lights shining in your face, creep out sometime after 2 o’clock Sunday and get comfortable.

Halley’s comet is presently 3.2 billion miles (5.1 billion km) from Earth or more than half a billion miles beyond Neptune. But the Orionid meteor shower shrinks that to only 60 miles, at least for now. Clear skies!

4 Responses

  1. Hi Bob, seen 6 shooting stars the last couple of nights, here in Atlantic Canada. Not sure if they were Orionids or not as Orion wasn’t up for most of them. They were few and far between, not very bright, deep yellow, short period, no smoke trail and very slow. Maybe the slowest shooting stars I’ve ever seen.

    Very nice weather and dark skies though. First time we have had clear nights consecutively in a very long time. Lots of great constellations up in the morning now.

    1. astrobob

      Hi Peter,

      It doesn’t. It orbits the sun in the path of the comet, though over time, the trail spreads out. We pass through the trail as it orbits the sun.

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