The Orionids are a meteor shower that rains heavily on Earth every year in mid-autumn. It is no coincidence that he is considered one of the most beautiful among his “relatives”. Meteors that “leave” the constellation Orion are known for their brightness and speed. This makes it extra exciting to watch them.
Orionids break into Earth’s atmosphere at a speed of about 66 km/s. Fast moving objects can leave glowing trails formed by hot debris. Such “fingerprints” remain in the sky on a moonless night from a few seconds to a couple of minutes. In addition, the largest of the meteors can form bright luminous balls in the sky.
How did the Orionids form?
Every October, Earth passes through the debris from Halley’s Comet as it approaches the Sun. Our planet’s orbit crosses the path of a distant walker twice a year. In May, a stream of cosmic dust moving away from the Sun forms the eta Aquarid Stream, and in October, approaching meteors create the Orionids.
Bits of space rock and ice that interact with our atmosphere to form the Orionids come from 1P/Halley. As a comet approaches the Sun, its core heats up and it throws particles of ice and rocky dust from its surface into the surrounding space. When such particles collide with Earth’s atmosphere, they become meteors that burn up in the atmosphere of our planet.
Earth’s passage through the stream of dust left behind by Halley’s Comet as it approaches the Sun lasts several months, but meteor activity tends to be low until mid-October as we approach the center of the cosmic wanderer’s orbit. In 2022, the maximum activity will occur on October 21. At this time, the average number of light trails is expected to be around 20 per hour.
Halley’s comet is one of the most famous space objects. This is the first comet for which an elliptical orbit was calculated and the period of rotation determined. By studying historical documents, the English astronomer Edmund Halley compiled the first catalog containing known observations of comets.
The scientist drew attention to the strange coincidence of the orbits of the comets observed by Apian in 1531, Kepler in 1607 and Halley himself in 1682. The astronomer assumed that it was the same comet and calculated its next appearance in 1758. The prediction was confirmed – Halley’s comet really orbits the Sun with a frequency of 75-76 year.
Halley last approached the Sun in 1984. This event became one of the most intense in the history of observation: the development of astronomical instruments and astronautics made it possible to send a research mission to the spacewalker. For example, the Soviet satellites Vega-1 and Vega-2 approached a comet, determined the structure of its nucleus and the process of coma formation.
In addition to a large amount of data, the comet filled outer space with new fragments that brightened meteor showers. The next “upload” is not expected until 2061: according to calculations, Halley will reach perihelion (the point in the orbit closest to the Sun) on July 27, 2061.
How to find meteors?
Orionids are not visible immediately after sunset: at this time they hide behind the horizon and appear in the sky at about 10 p.m. But the best time for sightings is from 1 AM to dawn. At this point the radiance (the point from which the meteors appear to emanate) is more than 30° above the horizon.
The bright moon can interfere with observations, but this year astronomers and amateurs are in luck: the Earth’s satellite is approaching the new moon, which will be on October 25, and therefore it will be illuminated at night with maximum activity of only 15-20%.
The Orionids get their name from the constellation Orion, in which the stream’s rays are found. During peak activity, the “source” will be to the east of the constellation, about 10° northeast of the bright orange star Betelgeuse (Alpha Orionis). This distance is approximately equal to the area covered by the clenched fist of the outstretched hand.
Where and how to look?
The best way to observe meteors is to lie in a comfortable sun lounger with your back tilted at a slight angle. You can also look vertically upwards, but you can see more meteors in the lower half of the atmosphere, because the view passes through a greater thickness of the atmosphere.
To see the Orionids, you shouldn’t just look towards the constellation Orion, NASA experts advise – meteors will be visible in different parts of the night sky. In fact, the Orionids are best viewed from 45 to 90 degrees from the beam. From this angle, they will look longer and more spectacular. If you look directly at the beam, the meteor trails will appear shorter.
Experts from the International Astronomical Society recommend looking south over the horizon. In this case, in addition to the Orionids, it will be possible to observe several other less active currents coming from the constellations Taurus, Gemini and Leo.
The Taurids will move slower than Halley’s stream, while the Gemini and Leo Minor meteors will be just as fast but less bright than the Orionids. These are small streams, but even in them it will be possible to consider up to 2 meteors per hour. At the same time, the Taurids this year can give rise to fireballs – large and bright objects.
Human eyes need some time to adjust to the dark, so don’t expect discoveries in the first few minutes. At the same time, the number of stars visible in the sky is a good indicator of the correct location. The more of them, the less artificial light and cloudiness interfere, making it more likely to see a star shower.
Finally, if you are unlucky and the sky was too cloudy on the night of the observation, you can try the next night: the scientists believe that the great activity in the current will continue for several days.
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On the cover: Brocken Inaglory, CC BY-SA 3.0, via Wikimedia Commons