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Appointment with the sky: the face of the Moon, between Jupiter and Saturn
During the moonless nights of this weekend we will enjoy good conditions to observe the Orionids, a meteor shower created by the famous Halley's Comet.
The maximum of activity will take place next Wednesday, October 21.
Also, in this month, we have
four very bright planets
observable with the naked eye.
How to observe them
Like every October, the Orionids faithfully attend their annual appointment.
They can be seen throughout the month, reaching their maximum activity on the nights of October 20-21 and October 21-22, at which time we can see about 20 shooting stars per hour.
The Orionids are fast and relatively large meteors, their speeds can exceed 200,000 kilometers per hour and they usually leave yellow or greenish trails that can last several seconds.
Without a doubt it is
one of the most beautiful meteor showers of
the year.
As its name suggests, the radiant of this meteor shower is in the constellation Orion and, more specifically, near the bright star Betelgeuse, but it is not necessary to know this star or this constellation to observe the meteors that can appear anywhere side of the celestial vault.
As the radiant is relatively close to the celestial equator,
the Orionids can be observed from both the northern and southern hemispheres
.
The new moon took place on Friday, October 16, so on Saturday and Sunday nights the moon will appear as a thin crescent edge that will be seen in the west after sunset and will go to bed at around 8:00 p.m. Saturday) or 21.00 (Sunday).
Our satellite will therefore not be a hindrance this year to observe the Orionids.
During these days, Orion will reach a good height above the horizon around 11:30 p.m.
It will be an excellent time to try to see the meteors appear among the bright stars that populate this region of the sky.
On peak nights (next Tuesday and Wednesday), the Moon will already be a little higher and will be visible until 1.00 or 2.00 in the morning, but
the sky will leave us very dark for the rest of the night
.
It is always convenient to look to the southeast from northern latitudes (to the northeast if we are in the southern hemisphere), trying to encompass as large a region of the celestial vault as possible.
At the beginning of the observation you have to have a little patience, while our eyes get used to the darkness, but after about twenty or thirty minutes, we should already begin to see the odd meteor.
And if the Orionids are not doing well, we can always take the opportunity to observe the planets that look splendid throughout the month of October, especially Mars that has just passed through its opposition on the 13th and is still frontally illuminated and visible throughout the night.
Also Venus, who rises now at around 5 am, shines ostentatiously at sunrise.
Finally,
Jupiter and Saturn continue to form a showy pair
that is closing distances between them until the moment of its maximum approach arrives in the next December.
Fragments of the Halley, the King of Comets
Every year, the Earth, in its translational movement around the Sun, twice passes through annular regions populated by the fragments left by the famous periodic comet 1P / Halley that visits us once every 76 years.
When one of these fragments (or meteoroids) falls into the Earth's atmosphere, it is calcined by 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 about 100 kilometers high.
In May the first passage of the Earth occurs through one of those areas
in which fragments of the Halley are abundant
, thus creating the rain called 'Eta Aquarids'.
Now in October, go through the second zone creating the Orionids.
The Halley is an
extremely dark rock
(its albedo is 0.03) and very elongated: it is 16 kilometers long by 8 kilometers wide.
It received its name from the astronomer Edmund Halley, although this was not its discoverer since the comet had been known since ancient times.
However, it was Edmund Halley who calculated its orbit in 1705 according to Newton's theory, predicting the return of the comet for the year 1759.
Halley died in 1742 and
could not witness the arrival of the comet in that year
.
However, the comet was greeted with great anticipation as it was a spectacular triumph of Newton's theory of gravitation.
From ancient China to Mark Twain
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 can most certainly 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 it was still another century to link this meteor shower with the king of comets, specifically until 1983, when the Canadian astronomer BA McIntosh and the Slovakian A. Hajduk published an article in which they
unambiguously established that the origin of the Orionids was the famous Halley
.
The Halley is the most famous of the comets, perhaps because it is the only one visible to the naked eye that
develops a very bright tail
and can be seen twice during a human lifetime.
Mark Twain always felt attached to this comet: the writer was born in November 1835, during one of the Halley's visits and in 1909 he wrote "I arrived with Halley's Comet in 1835. He comes back again next year and I hope to go with him. . "
And, indeed, Twain died the day after the Halley perihelion that took place on April 20, 1910.
In 1986 we witnessed the most recent approach
of this sensational comet that will not visit us again until the year 2062.
Rafael Bachiller
is director of the National Astronomical Observatory (National Geographic Institute) and academic of the Royal Academy of Doctors of Spain.
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