Astronomers are waiting to see if a normally calm meteor shower makes a show on Monday night. There is a possible outburst of the Tau Herculids, but the keyword is “potential.”
Almost every month, we have a significant meteor shower where, under ideal conditions, you can expect between 20 and 120 meteors per hour. This happens when the Earth plows through the remnants of a passing comet or asteroid.
Tau Herculids are a periodic meteor shower. In some years there is nothing to see and in others a handful of meteors are seen. Knowing what will happen in a given year can be difficult to predict. The shower usually runs from May 19 to June 14 and arrives in the evening from May 30 to 31.
But 2022 is a special year. In 1995, comet 73 / P Schwassmann-Wachmann 3, responsible for this rain, broke in about 40 pieces. It is this cloud of rubble through which the Earth now runs.
The Hubble Space Telescope’s Advanced Survey Camera captures an image of Comet B fragment 73P / Schwassmann-Wachmann 3 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 that is very important in this case.
The bigger the better
Meteorites are remnants the size of a grain of dust (or larger) that burn in the atmosphere. Its high speed produces the glow 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 a millimeter in size but travel at a dizzying speed of 60 km / s.
But in the case of the Herculean tau, the particles only enter the atmosphere at about 15 km / s. And, according to the American Meteorite Society, the debris moves in the same direction as the Earth. This means that they cannot increase much speed, so any meteor can be quite weak.
“As for geometry, meteors are taking over the Earth. As a result, the rain, the things we get, move at only 15 kilometers per second. So it moves a quarter of the speed of the Perseids.” said Peter Brown, Canada’s chair of meteorite astronomy research 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)
“A millimeter-sized perseid is about a third magnitude. A millimeter-sized Herculean tau is ninth. I would say [to get] Hercules tau spectacular, they must be centimeter in size, as very large, which is possible. I mean … the big joke or unknown is: what happened during the disintegration? Was there a lot more material? “
Where and when
If there is a spectacular spectacle, Canada is in an ideal location.
“Coincidentally, the time we go down the rubble track, whether it’s the ruins of the actual rupture, or even just the oldest rubble roads, is at 1:00 a.m. Eastern time, and they are good viewing conditions for virtually all of North America, “said Brown.
Meteor showers are usually named after the constellation from which the meteors appear to originate, called radiant. Imagine you see a meteor above you; if he drew an imaginary line 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 Hercules are a little different. The radiant can appear from different places in the sky for this type of comet. This year, the radiant will be in the constellation of Boötes.
This celestial letter illustrates the radiant of the Herculean tau. You can find the constellation of Boötes by finding the first star in the handle of the Big Dipper and tracing it to the brightest star in Boötes, called Arcturus. (American Meteor Society)
If you’re willing to risk this rain, it’s best to get to a dark sky spot, as the meteors could be quite faint, though Brown said some meteors can be 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, stretch and look up.
So how many can you expect to see?
Brown said some of the predictions he believes could be possible are 30 to 40 per hour. But there are others who ask for much more than that.
“There are people who say that if the comet’s rupture gets here, you’ll see thousands per hour, but that’s very speculative,” he said. “It’s going to take a lot of centimeter-sized objects … I mean, yes, it would be spectacular, but I think it’s kind of like a lottery ticket. But I hope I’m wrong.”
Although there is no spectacular spectacle, at least meteorite experts like Brown will be able to learn more about this comet and its rupture. And people will have enjoyed a night under the stars.
“It’s worth going out, but … temper expectations.”