COURSE Introduction to Astronomy (43) STELLAR MAGNITUDE. (1)
The record of the positions of stars in a catalog called esteleares lists is a fundamental baseline for important astronomical knowledge such as the determination of the time, the phenomena of precession and nutation, proper motion of stars. The earliest catalog was developed by astronomer Greek Hipparchus in 127 BC It contained the positions of 1080 stars divided into six classes according to their apparent brightness Arabs kept another catalog of stars called "Almagest" of Ptolemy, in this work we have inherited the custom to group the stars brightness classes or magnitudes. The classes of brightness were called magnitude, calling for the brightest of 1 st magnitude, 2 nd, 3 rd, 4 th, etc., until the 6 th magnitude, the latter are the faintest stars that distinguish somple view.
For magnitude means the apparent brightness of stars we see and dimensions of these stars.
In 1856 the astronomer Norman Pogson established the "Pogson scale" means a 1st magnitude star has an apparent brightness 2,512 times greater than a 2 nd magnitude star, this 2,512 light intensity greater than a 3 rd magnitude and so on. Pogson included the star Aldebaran and Altair to the base times the scale. These magnitude scales extending one hand toward zero and negative numbers, to encompass the brightest stars like the Sun and the Moon.
The apparent magnitude depends on the brightness of the star and the distance that is an example, Sirius has an apparent magnitude of -1.46 (the most brilliant of heaven, is to 9 light years away, while that Rigel is 2000 times more luminous, with a magnitude appears to be 0.08 at a distance 100 times greater).
COURSE Introduction to Astronomy (42) NAME AND TITLE OF THE STARS.
From the earliest civilizations, the stars are considered grouped into constellations. The names of the stars both from the Greeks such as Sirius, Procyon, Pollux, Castor, Regulus, Polaris, Arcturus, Canopus, The Pleiades, as the Arabs and the names of Alcor (weak), Mizar (veil) Vega (fall), Aldebaran (the follower), Deneb (the tail), Rigel (leg) Algol (star demon), Betelgeuse (shoulder Giant), and a few hundred names.
Unable to give nEombre to the huge number of stars raised the idea of \u200b\u200banother system of nomenclature that is most useful to astronomers.
In 1603, Johannes Bayer of Germany published a book called Uranometría, an atlas of star maps which showed the stars in each constellation alafabeto using Greek letters that followed the genitive of the Latin name for the constellation to which it belongs. Bayer
established an order of brightness within each constellation, so called to the brightest star, b which was brighter, g to the next and AASI on. The drawback of this classification is that only the Greek alphabet has 24 letters, while on average there are about 70 visible stars for each constellation. When the Greek alphabet were insufficient for a constellation Bayer resorted to the use of the lowercase letters of the Latin alphabet, complicating the method.
After the appearance of the telescope showed the existence of a greater number of stars and was raised again the issue of its name.
In 1712, the English astronomer John Flamsteed, was the first catalog with the help of the telescope, called Coelestis History Britannica, resorted to the use of numbers instead of letters, numbers assigned to each star according to the order in which they reached the meridian. Eventually
were improved telescopes, observing and millions of stars in each constellation, the stars are distinguished not by name, or letters, or numbers, if not by their position on the celestial sphere, ie by right ascension and declination.
COURSE Introduction to Astronomy (41) meteors.
A meteoroid is a piece of material, of variable size and shape located in interplanetary space may be attracted by the gravitational field of the earth and land on our planet.
Friction with the atmosphere there is a sharp rise in temperature causes a luminous phenomenon, visible, known as a meteor or shooting star.
When a meteor reaches a high brightness (magnitude -4 or higher) is called bólido.Por Finally, when a meteoroid manages to reach the earth's surface is called a meteorite.
For meteors visible with a magnitude of between 1 and 6 have a weight between 2 mg and 2 grams. But there are many smaller fragments that cause meteors undetectable to the naked eye, being the total amount of matter falling into a meteoric day on Earth, between 1000 and 10000 tons.
sporadic meteors can appear anywhere in the sky, or forming the so-called meteor showers. Any clear night is suitable for the observation of sporadic meteors, but are more frequent in the second half of the night.
During a meteor shower, meteor rate is usually higher. Some have come to rely 2,000 meteors per hour. If during a meteor shower meteor traces are represented in a star map, we see that they all seem to come from a point, that point is called radiant. Meteor showers are named for the constellation which is the radiant is located, such as Leonidas, whose radiant is located in Leo, Taurid (in Taurus), the Orion (in Orion), Persians (in Perseus), etc ...
As for the origin of meteor showers, they are associated with the cometary orbits, occur when the Earth crosses the orbit of a comet. The swarms of meteoroids and debris are remnants of comets that orbit the Sun in elliptical orbits. Sporadic meteors are caused by meteoroid swarms of old waste.
