Astro Bob: Broken comet may spark meteor outburst May 30-31

The element of surprise makes meteor showers fun and exciting to watch. You never know exactly when a fiery flash will dart past. If you like that kind of surprise, you'll going to love (or hate) the Tau Herculids.

Comet 73P/Schwassmann-Wachmann, discovered by German astronomers Friedrich Schwassmann and Arno Wachmann in 1930, is the "parent" of the shower. Material shed by the comet during its 5.4-year circuit of the sun leaves a dust trail around its orbit that Earth crosses in May and June. Typically, you might see a meteor or two per hour, the reason the Tau Herculids don't get much attention. But this year could be dramatically different.

73P suffered a major disruption in 1995, breaking apart into multiple pieces, several of which returned as comets of their own in 2006. With an original size of around 0.8 miles (1.3 km) across, 73P has since disintegrated to produce more than a hundred meter-sized or larger fragments. Cometary cataclysms like this one create concentrated filaments of ice, dust and rocky debris within the broader, more diffuse stream of dust in the comet's orbit.

Here's where it gets interesting. Two independent studies by German and Japanese meteor researchers predict that the Earth will pass just 37,000 miles (60,000 km) from the 1995 breakup filament on the night of May 30-31. That may be close enough to give us a great show of meteors, maybe even a "storm," when numbers exceed 1,000 per hour. That said, no one's absolutely sure what to expect.

The prediction rests on whether the breakup was powerful enough to propel debris out ahead of the comet, in which case we would encounter the larger pieces — those big enough to produce a spectacular show of slow-moving fireballs. Yes! But if 73P busted apart with less force, the particles might be too tiny to generate meteors bright enough to see, yet still produce a strong shower.

Should that happen, you'll still be able to listen to the shower. Yes, you heard that right. Radio waves from a transmitter (like an AM radio station) can bounce off the trail of ionized air left by meteoroid's passage through the atmosphere and produce audible pings ("echoes") on a radio receiver. Whether you watch the shower or not you'll know it's occurring by tuning into livemeteors.com and listening for an uptick in the number of pings.

Contributed / Vidur Parkash

To sum up then. We'll either see a spectacular meteor storm, a smattering of slow, faint meteors or nothing at all. In other words, it's a crap shoot. Myself, I never gamble money. But I will gamble time and travel if it means a seeing a potential spectacle at the end of the road. Still, I'm crossing my fingers for clear skies right here at home.

The shower, should it occur, will last just a few hours centered on 5:00 Universal Time (UT) May 31. For U.S. and Canadian time zones that means late Monday night, early Tuesday morning May 30-31:

Shower peak times
May 31 — 1 a.m. Eastern Daylight Time
May 30 — 12 midnight Central Daylight Time
May 30 — 11 p.m. Mountain Daylight Time
May 30 — 10 p.m. Pacific Daylight Time (Twilight will interfere in the Pacific Northwest)

Best case scenario, you'll see a great show no matter where you live (except in big cities, of course), but to improve your odds, find a dark-sky site in the countryside. Remember to bring a reclining chair for comfort and blanket for warmth. Start watching about an hour before the peak.

Contributed / Stellarium with additions by Bob King

The meteors will appear to dart from a spot in the sky called the radiant, located between the bright,orange star Arcturus and the end of the Big Dipper's handle. Fortunately, that's high in the southwestern sky for observers in the U.S., so just lie back and watch. Normally, you'd expect Tau Herculids to originate from neighboring Hercules. Not this time. Because the shower debris was forcefully ejected ahead of the comet rather than trickling down the tail, the radiant shifted westward into Boötes the Herdsman.

It may also be possible to record the faint glow of the meteoroid trail itself — the stream of sparkling dust left by the comet. One lobe lies in eastern Leo, off the lion's tail end, the other in the constellation Equuleus at the eastern horizon. Leo is much better placed, making it the better choice.

While it's doubtful anyone will see it with the naked eye, a DSLR or mirrorless camera from a supremely dark site may do the trick. Use a wide-angle lens and time exposure. Set your ISO (sensitivity) to at least 3200, with the lens wide open to let in the maximum amount of light, then expose for at least 30 seconds.

Let's hope for good weather and a great shower. If clouds interfere Italian astronomer Gianluca Masi will livestream the event starting at 11 p.m. CDT, May 30.

"Astro" Bob King is a freelance writer for the Duluth News Tribune.