Something astronomically exciting could happen at the end of this month. On the evenings of May 30 and 31, astronomers around the world will observe the sky to see if a new meteor showerexpected for nearly 100 years.
The brief, but intense meteor show would be due to one comet which split in 1995 and which, it seems, is still fragmenting. According to NASA, a new meteor shower could occur in a week, the Tau Herculidswhich perhaps rank among the best annual meteor show.
The meteors of the Tau Herculids are fragments of the comet 73P / Schwassmann-Wachmann 3 (SW3). Two German astronomers, Arnold Schwassmann and Arno Arthur Wachmann of the Hamburg Observatory, had identified this comet in the 1930. SW3 orbits the sun every 5.4 years. But being very weak, SW3 wasn’t seen again until the late 1970s. In addition to its weakness, one reason astronomers could no longer spot SW3 was that they were looking in the wrong place. Their inaccurate orbital calculations were due to close passes near Jupiter, which had changed the comet’s orbit.
Later, SW3 had appeared quite normal until 1995, when astronomers realized that it had become about 600 times brighter and had gone from being a faint spot to being visible to the naked eye as it passed. Upon further investigation, the astronomers realized that SW3 had shattered into several pieces, scattering its own orbital trail of debris. By 2006, it had nearly shattered into 70 pieces and has continued to fragment further since then. Comet SW3 returned in 2011 but was not well positioned for observers that year, as it had mostly remained behind the sun. So we couldn’t learn anything from that passage.
Now SW3 could be back on show. Bill Cooke, who heads NASA’s Meteoroid Environment Office, said: “this will be an all or nothing event. If the SW3 debris was traveling at more than 354km / h when it separated from the comet, we could see a nice meteor shower. If the debris had slower ejection rates, nothing will reach the Earth and there will be no meteors from this comet ”.
The right conditions
For there to be a good meteor shower in 2022, three pieces of the puzzle must fit together. First, a large number of particles must have been ejected from the comet’s nucleus during its breakup in 1995. And this appears to be true, as the images taken at the time indicate. Second, the comet’s rupture was supposed to eventually push the material forward in its orbit. Since a comet orbits the sun and ejects material, we assume that the particles go in all directions. Those pushed back will take on a slower speed and, governed by the laws of gravity, will fall closer to the sun. When they are closer to the sun, they will accelerate and over time, they will pass by the comet in their smaller orbits and precede it.
Eventually, the comet must eject the material at a speed fast enough to assume this new orbit. To do this, a speed of about 27 meters per second is required. This is faster than normal, but the great outburst and rupture of the comet’s core in 1995 may have been strong enough to produce this speed. If all three of these conditions are met, we will have the perfect storm.
This meteor shower – the Tau Herculids – got its name in 1930 when the comet passed very close to Earth. Some observers are said to have seen a short-lived meteor shower in the 1930s. But this claim has been questioned. Since then, the swarm has been either non-existent or lackluster, although it is still on the American Meteor Society’s list of meteor showers, which indicates its duration from May 19 to June 14.
Most meteor showers are named after the point in the sky from which they appear to radiate. And this swarm will probably be known forever as Tau Herculids because that was the position calculated when the comet was discovered in 1930. But observers have never seen meteors from this comet radiate from this position in the sky. Due to the gravity of the giant planet Jupiter, the radian has shifted. It is now located in the western Bootes constellation, near the bright star of Arcturus, near the globular cluster M3.
How to watch the meteor shower
In 2022, the Moon will be new the day before the expected peak for this meteor shower. So fortunately the satellite will not obstruct the vision of the phenomenon. Calculations from different teams yielded three different peaks, all over a 22-minute time frame. One places the peak at 05:04 UTC on May 31, 2022; the other two at 04:55 UTC and 05:17 UTC.
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