Astronomers are waiting to see if there will be a normal quiet meteor shower on Monday night. There is a potential outbreak of the Tau Herculians – but the key word is “potential”.
Almost every month we get a big meteor shower, in which – under ideal conditions – you can expect from 20 to 120 meteors per hour. This happens when the Earth drills debris left over from a passing comet or asteroid.
Tau Herculids is a periodic meteor shower. In some years there is nothing to see, and in others a handful of meteors can be seen. Knowing what will happen in a given year can be difficult to predict. The shower usually lasts 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 – disintegrated on about 40 pcs. It is this cloud of debris that the Earth is now racing through.
The Hubble Space Telescope Advanced Camera captures Comet 73P / Schwassmann-Wachmann 3 fragment B on April 18, 2006 (NASA, ESA, H. Weaver [APL/JHU]M. Mutchler and Z. Levay [STScI])
The only problem is that we don’t know how many pieces there are or how big they can be. And this is very important in this case.
The bigger the better
Meteors are debris the size of dust grains (or larger) that burn up in the atmosphere. Their high speed creates the brilliance and tail we see. The angle at 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 mid-August. These meteors are millimeters in size, but move at a staggering speed of 60 km / s.
But in the case of the Tau Herculids, the particles enter the atmosphere at only about 15 km / s. And, according to American Meteor Society, the debris is moving in approximately the same direction as the Earth. This means that they cannot accumulate much speed, so all meteors can be quite weak.
“Like geometry, meteors are catching up with the Earth. As a result, the rain, the things we get, are only moving at 15 kilometers per second. So it’s moving at a quarter of the speed of the Perseids,” said Peter Brown, Canadian research chairman. meteor astronomy and professor at Western University in London, Ont.
Astronomers measure the brightness of objects in terms of magnitude. The lower the number, the brighter the subject.
(CBC News)
“A millimeter-sized Perseid is about a third. Tau Herculid with a millimeter size is the ninth magnitude. I would go so far as to say [to get] spectacular tau Herculids, they should be the size of a centimeter, as really large as possible. I mean … the big wild sign or the unknown is: what happened during the breakup? Was there much more material? “
Where and when
If there is a spectacular show, Canada is in the perfect place.
“Coincidentally, the time for where we will cross the trail of debris, whether it’s debris from actual decay, or even just older traces of debris, is about 1 a.m. Eastern Time and has great viewing conditions for almost all of North America. “Brown said.
Usually meteor showers are named after the constellation from which meteors seem to originate, called a radiant. Imagine seeing a meteor above you; if you trace an imaginary line to where it comes from, it would be radiant. For example, for the Perseid meteor shower, the radiant is in the constellation Perseus.
However, the Tau Herculids are a little different. The radiant can appear from different places in the sky for this type of comet. This year the radiant will lie in the constellation Boötes.
This diagram of the sky illustrates the radiance of the Tau Herculians. You can find the constellation Boötes by finding the first star in the handle of the Big Dipper and tracing it back to the brightest star in Boötes, called Arcturus. (American Meteor Society)
If you’re willing to take a risk with this shower, it’s best to get to a place in a dark sky, as meteors can be quite weak, although Brown said some meteors can get quite bright.
And just because the radiant is in Boötes doesn’t mean you have to look in that direction. Just take a blanket, lie down and look up.
So how much can you expect to see?
Brown said some of the estimates he thinks are possible are 30 to 40 an hour. But there are others who are calling for much more than that.
“Some people say that if the comet’s decay comes here, you’ll see thousands an hour, but that’s very speculative,” he said. “This will require very large objects the size of a centimeter… I mean, yes, it would be spectacular, but I think it’s something like a lottery ticket. But I hope I’m wrong.
Even without the spectacular show, at least meteor experts like Brown will be able to learn more about this comet and its decay. And people will enjoy a night under the stars.
“It’s worth going out, but limit your expectations.”
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