If the predictions are correct, some places on Earth will see an intense meteorite storm later this month.
An outbreak of Tau Herculids’ annual rainfall is expected to last about an hour on May 30 or 31 (the date depends on where you live in the world).
It could fill the sky with shooting stars, or it could be a complete, total envelope.
But either way, it will be exciting for astronomers like Jonti Horner of the University of South Queensland.
“A spectacular storm is one of the things I most want to see in the night sky that I’ve never been lucky enough to see,” Professor Horner said.
“Even if that doesn’t lead to a big storm in itself, it means that the next time we have a big storm, we can predict it much, much better thanks to what we’ve learned from it.”
So what is Tau Herculid meteor shower? And where is the best place in the world to see it (if it happens)?
It’s usually not something to write at home
Tau Herculids is not new, but it is much less rainy.
Each year, the Earth moves through the debris stream of a small comet called 73P / Schwassmann-Wachmann 3, or SW3 to shorten.
SW3, which was discovered in the 1930s, orbits the Sun every 5.4 years, leaving a trail of debris behind it.
When it was first discovered, astronomers predicted that we should see meteors from a point near the star Tau in the constellation of Hercules, which gives it its name.
The radiant point of the meteor in relation to the constellations of Boötes and Hercules (southern hemisphere perspective) (Stellarium / ABC: Genelle Weule)
It is rapidly advancing 90 years and the radiant point has shifted to the neighboring constellation of Boötes thanks to SW3’s upcoming regular encounters with Jupiter, which have altered the comet’s orbit over time.
The best meteor showers, such as Geminids, can produce up to 50 meteors per hour (depending on where you are in the world).
But the Tau Herculids tend to value just one mention on the rain list to see why we’ve only seen a handful of meteors since the comet was discovered.
“Most of the time it’s really rubbish, but there’s a chance there’s something special this year,” Professor Horner said.
If the predictions are correct, the Tau Herculids could rise at rates far beyond what we normally see even in the best rains.
So what has changed?
Comet cloud disintegrating
For the first time, the Earth can find the tip of a thin filament of javelin-shaped debris placed in 1995, when SW3 separated.
“In 1995, when the father of this meteor shower disintegrated, more than 70 large chunks were observed, and a lot of dust and debris,” Professor Horner said.
“And in the years that followed, we continued to see it unravel.”
Comet Schwassmann-Wachmann-3 disintegrated in 1995. (Supplied by: NASA / JPL-Caltech)
But if the encounter will be spectacular, well, or just nothing happens to the geometry.
“We’re very close to the end of the powder javelin that was launched in 1995 and the question of whether or not we’ll see anything depends on how long that spear is,” Professor Horner said.
This will depend on the speed at which the dust travels.
Instead of passing through the comet’s wreckage at a sharp angle, the Earth scratches the edge of the comet’s orbit like the smooth fusion of cars on a road traveling at the same speed.
This means that Tau Herculid meteors tend to move very slowly (about 16 kilometers per second) and are not very bright.
“If the debris was released at normal speed, comets release debris as they travel around the Sun, the javelin will be too short to reach us,” Professor Horner said.
“But because [the comet break-up] it was such a violent event … there is a possibility that some of this dust has been released at a faster than normal speed. “
“If it were fast enough and a lot of dust could reach us, it means we could see a meteor storm.”
If it doesn’t, the next big Tau Herculid storm is not expected to happen until 2049, and meteorite rates may be lower as the dust spreads over time.
Meteor showers and storms
Meteor storms can cause more than 1,000 meteors per hour if you live somewhere where the radiant spot is directly above your head.
In 1872 and 1885 “the stars fell like rain” when the Earth crossed a stream of debris left by a comet that disintegrated in 1846.
A painting of the Andromeda meteor shower over France on November 27, 1872. (Wikimedia Commons: Amedee Guillemin)
The event, known as the Andromedid or Bielid meteorite storm, produced thousands of meteors per hour, but had not been seen since 1885.
Another meteor shower in the northern hemisphere known as the Leonids has risen to storm level several times over the past 200 years.
One of the most spectacular happened in 1966, when thousands of meteors per minute fell through the Earth’s atmosphere during a 15-minute storm.
The last meteorite storm in the Leonids occurred in 2002.
It is thanks to the regular eruptions of the Leonids that astronomers are doing quite well to predict when new meteor showers and storms will occur.
Last year they accurately predicted a new rain known as the Finlayids.
So who can see it?
Unless the prediction is over, we are unlikely to see the Tau Herculid storm from Australia.
Its peak is expected at 3 p.m. (AEST) on May 31st.
Not only that during the day in Australia, but the constellations from which meteors radiate will be below the horizon at that time.
But the peak will be visible in North America and parts of South America and the Pacific (the further north, the better the fares), where it is still night.
“It’s perfect for Baja California because at that time [11pm May 30 PDT]the radiant will be almost above, “Professor Horner said.
And as it happens during the new moon phase, the night sky will be dark.
While it is almost certain that Australia will miss the main event, Professor Horner said there was a very remote possibility that people living in the eastern half of the country would still be lucky enough to spot a meteor on the horizon. northeast an hour or so. sunset on May 31st.
The farther north you are, the higher the radiant above the horizon.
“Don’t make special plans to go out, but if you’re out, keep your eyes peeled,” he said.
“If we miss you [the peak] of a couple of hours and it’s really spectacular, then maybe we’re still in a state of descent and maybe we still see a few of them at sunset and soon after.
“Meteors will be revealing, they will move incredibly slow compared to normal shooting stars.”
It may also be possible to capture a strange meteorite from dust tracks established before 1995.
“There are probably currents from previous comet passages around the Sun, and if it was preparing to undo, it could be more active than we thought,” Professor Horner said.
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