Are we in for a spectacular meteor shower? Astronomers aren't sure, but suggest looking up tonight

·4 min read
A Perseid meteor streaks over Starfest, a star party held annually in southwestern Ontario each August. While the Perseids are a fairly consistent and reliable shower, the shower that is upon us — the tau Herculids — aren't. This year, however, could be a breakout year for the normally quiet meteor shower. (Submitted by Malcolm Park - image credit)
A Perseid meteor streaks over Starfest, a star party held annually in southwestern Ontario each August. While the Perseids are a fairly consistent and reliable shower, the shower that is upon us — the tau Herculids — aren't. This year, however, could be a breakout year for the normally quiet meteor shower. (Submitted by Malcolm Park - image credit)

Astronomers are waiting to see if a normally quiet meteor shower puts on a show Monday night. There's a potential outburst from the tau Herculids — but the key word is "potential."

Almost each month, we get a major meteor shower where — under ideal conditions — you can expect anywhere from 20 to 120 meteors an hour. This occurs as Earth plows through debris left over from a passing comet or asteroid.

The tau Herculids is a periodic meteor shower. In some years, there's nothing to see and in others a handful of meteors are visible. Knowing what will happen on any given year can be tough to predict. Typically, the shower runs from May 19 to June 14 and peaks on the night of May 30–31.

But 2022 is a special year. In 1995, Comet 73/P Schwassmann-Wachmann 3 — which is responsible for this shower — broke apart into roughly 40 pieces. It's this debris cloud through which Earth is now racing.

NASA, ESA, H. Weaver [APL/JHU], M. Mutchler and Z. Levay [STScI]
NASA, ESA, H. Weaver [APL/JHU], M. Mutchler and Z. Levay [STScI]

The only issue is, we don't know how many pieces there are or how big they might be. And that matters very much in this case.

The bigger the better

Meteors are dust grain-sized (or larger) debris that burn up in the atmosphere. Their high speed produces the glow and tail we see. The angle in which these meteors enter our atmosphere is also important.

As an example, one of the best meteor showers of the year is the Perseids, which peak in the middle of August. These meteors are millimetre-sized but are travelling at a breakneck speed of 60 km/s.

But, in the case of the tau Herculids, particles are only entering the atmosphere at roughly 15 km/s. And, according to the American Meteor Society, the debris is moving in roughly the same direction as Earth. This means they can't build up a lot of speed, so any meteors could be quite faint.

"The way the geometry is, the meteors are catching up to Earth. So as a result, the shower, the things we get, are moving at only 15 kilometres a second. So it's moving one quarter of the speed of the Perseids," said Peter Brown, Canada research chair in meteor astronomy and a professor at Western University in London, Ont.

Astronomers measure the brightness of objects in terms of magnitude. The lower the number, the brighter the object.

CBC News
CBC News

"A millimetre-sized Perseid is about third magnitude. A millimeter-sized, tau Herculid is ninth magnitude. I would go so far as to say [to get] spectacular tau Herculids, they have to be centimetre-size, like really big, which is possible. I mean … the big wildcard or unknown is: what happened during the disintegration? Was there a lot of bigger material?"

Where and when

If there is a spectacular show, Canada is in an ideal location.

"By chance, the timing of where we're going across the trail of debris, whether it's the debris from the actual breakup, or even just older debris trails, it's all about 1 a.m. Eastern Time, and it's great viewing conditions for pretty much all of North America," Brown said.

Normally, meteor showers are named for the constellation from which the meteors seem to originate, called the radiant. Imagine you see a meteor above you; if you traced an imaginary line to where it came from, that would be the radiant. For example, for the Perseid meteor shower, the radiant is in the constellation Perseus.

However, the tau Herculids are a bit different. The radiant can appear from different locations in the sky for this type of comet. This year, the radiant will lie in the constellation Boötes.

American Meteor Society
American Meteor Society

If you're willing to take a chance on this shower, it's best thing to get to a dark-sky location since the meteors could be quite faint, though Brown said some meteors can get quite bright.

And just because the radiant is in Boötes, that doesn't mean you have to look in that direction. Just grab a blanket, lie down and look up.

So how many can you expect to see?

Brown said some of the predictions that he believes could be possible are 30 to 40 an hour. But there are others who are calling for far more than that.

"Some people say if the comet break-up gets here, you'll see thousands an hour, but that's massively speculative," he said. "That'll need lots of big centimetre-sized objects … I mean, yeah, it'd be spectacular, but I think that's like a lotto ticket sort of thing. But I hope I'm wrong."

Even if there isn't the spectacular show, at the very least meteor experts like Brown will be able to learn more about this comet and its break-up. And people will have enjoyed a night under the stars.

"It's worth going out, but … temper expectations."

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