This weekend the brightest meteor shower arrives: the Orionids
This weekend the maximum activity of the Orionids takes place, a meteor shower created by the famous Halley's Comet. Due to the crescent moon, it will be preferable to observe shooting stars after midnight.
Few, but very bright
The Orionids take place from October 4 to November 10, approximately, reaching their maximum activity on the nights of October 20 to 21 and 21 to 22, at which time we can observe about 20 shooting stars per hour. in optimal conditions. It is therefore a much less abundant meteor shower than the Perseids or the Leonids, but the Orionids have the peculiarity that half of them are very bright (some shine brighter than the planet Venus).
And the Orionids are fast and relatively large meteors, their speeds can exceed 60 kilometers per second and they usually leave yellow or greenish trails.. In sufficiently dark skies, some of these contrails may remain visible for several seconds.
The yellow and greenish trail of an Orionid
As its name indicates, the radiant of this meteor shower is located in the bright constellation of Orion and, more specifically, near the bright star Betelgeuse, but you do not need to know this star or this constellation to observe the meteors that can appear by any side of the celestial vault. Since the radiant is relatively close to the celestial equator, the Orionids can be observed from both the Northern and Southern Hemispheres.
On the nights of this weekend, the Moon will be in its first quarter, since the full moon will take place on October 28. Orion will reach a good height above the horizon around 11:30 p.m., and the Moon will go to bed shortly after, leaving the background of the sky very dark.. For all these reasons, it will be preferable to observe the meteors after midnight. If we observed before that moment, it would be advisable to look away from the Moon's position to try to locate a bright bolide.
As the meteor activity lasts until November 10, we can try to continue observing the following nights, as the week of October 22 to 27 progresses, but the Moon will grow as the days go by, getting more and more in the way of the observation of shooting stars.
Pieces of Halley's Comet
Every year, the Earth, in its orbital movement around the Sun, twice passes through annular regions populated by the fragments left by the famous periodic comet 1P/Halley, which visits us once every 76 years.. When one of these fragments (or meteoroids) falls into the Earth's atmosphere, it burns up due to friction with the air, thus creating the luminous glow that we know as a meteor or shooting star.. Typically, the most common meteors that we observe with the naked eye are produced by particles a few millimeters to a few centimeters in size that burn up about 100 kilometers high.
Halley's Comet in its passage in 1986 . Liller
In May, the first passage of the Earth through one of those areas in which fragments of Halley abound, thus creating the rain called 'Eta Aquarids'. Now in October, it passes through the second zone creating the Orionids.
The king of comets
Halley is the most famous comet and one of the brightest.. It received its name from the astronomer Edmund Halley, although he was not its discoverer since the comet had been known since ancient times.. However, it was Edmund Halley who calculated its orbit in 1705 in accordance with Newton's theory, predicting the return of the comet for the year 1759.. Halley died in 1742 and was unable to witness the comet's arrival that year.. However, the comet was received with great expectation as it was a spectacular triumph of Newton's theory of gravitation.
The oldest records of observations of Halley's Comet date back to the 3rd century BC. when it was sighted by Chinese astronomers on one of their visits. Also in China, but many centuries later, in the s. VI d. C, a meteor shower was noted for the first time that, with great certainty, can be identified with the Orionids.
The radiant of this meteor shower was located by the British astronomer Alexander Herschel (grandson of the great William Herschel) in the 1860s.. But we still had to wait another century to relate this meteor shower with the king of comets, specifically until 1983, when the Canadian astronomer BA McIntosh and the Slovak A. Hajduk published an article in which they established unambiguously that the origin of the comets Orionidas was the famous Halley.
Rafael Bachiller is director of the National Astronomical Observatory (National Geographic Institute) and academic of the Royal Academy of Doctors of Spain.