A modest meteor shower is on tap this week. Named the Eta Aquariids (AY-tuh Uh-QWAR-ee-ids), their parent is Halley's Comet, which last passed by Earth in 1986 and will again in 2061. If you're currently about 55 years old or younger you've got a reasonably good chance of seeing it on that future date. I spent many nights with the comet in 1985-86, and unless I make it to 107 I expect they were my last. Halley's reaches it greatest distance from the sun in late 2023 — beyond the planet Neptune — then slowly ambles back toward the sun.
The comet returns about every 76 years, roughly a human lifetime, but the Earth passes through its trail of dusty debris twice a year, in early May and again in October. When Earth intersects the comet's orbit in May, Halley fragments stream from the direction of the star Eta Aquarii, which gives its name to the meteor shower. Five and a half months later in October, the planet glides across the orbit a second time, and meteors streak from Orion during the Orionid shower.
Each time Halley dives into the inner solar system, the sun vaporizes some of its ice, releasing water and carbon dioxide along with dust and rocks that range in size from sand grains to M&M's. During its March 1986 flyby, Europe's Giotto spacecraft discovered that water boiled off the comet at the rate of 16 tons a second! Don't worry. It won't run out of ice anytime soon. With a diameter of 6.8 miles (11 km) astronomers estimate Halley will still be making the rounds for about the next 200,000 years.
The Eta Aquariid meteor shower is active from late April through May but peaks during the early morning hours on Wednesday, May 5. If clouds threaten, May 4 or 6 are good backup dates, too. Observers in Caribbean and Southern Hemisphere can see up to 50 meteors per hour under a dark, moonless sky, making this one of the best meteor showers of the year. Those of us in the U.S. will spy about half that number because the radiant, the point in the sky from which the meteors stream, doesn't rise above the southeast horizon until after 3 a.m., not long before the start of morning twilight.
The thick crescent moon will also be out, but it won't rise until just before 4 a.m., so it won't put too big of a hurt on shower counts. Eta Aquariids are swift, traveling at 148,000 miles an hour (66 km/sec), and often leave persistent glowing trails called trains. For the best view, I'd suggest sitting halfway up in a reclining chair and facing southwest or northeast. That way you won't be facing the moon.
While you might spot a few earthgrazers anytime after midnight — shower meteors that skim the Earth's atmosphere on long, shallow paths — the best time to watch will be from about 3 a.m. to 4:30 a.m. While you're out waiting for the next Halley-mote to brand the sky, look for Jupiter and Saturn off to the southeast. A steadily-held pair of 10x binoculars will show all four of Jupiter's moons that morning. Callisto, Ganymede and Io (left to right) will look like tiny stars just to the left (east) of the planet, while Europa shines alone to the right (west) of Jupiter.
For now, the forecast looks great for my location, so I plan to watch and take pictures. I hope you can, too. To photograph meteors, you'll need a DSLR camera, wide-angle lens (35 mm, 24 mm, 16 mm) and a tripod.
First, set the lens and exposure to manual (M). Then use your camera's live view feature and magnifying glass button to sharply focus on a bright star. Open the lens all the way to let in the maximum amount of light (f/2.8, 3.5, 4 or the like) and expose for 30 seconds at ISO 1600 for good results. The more photos you take, the better your chances of snagging a meteor.
"Astro" Bob King is a freelance writer for the Duluth News Tribune. Read more of his work at duluthnewstribune.com/astrobob.