By popular demand, and personal weakness with this star, I will take leave momentarily aside the stars and constellations near Polaris (called circumpolars) to speak about a star well away from it, Antares.
As shown in the image, Antares is in the constellation Scorpius, one of the Zodiac constellations so, therefore, his name is well known to all. Unlike other constellations, with Scorpio is easy to imagine why astronomers from several different civilizations were able to find the shape of a scorpion in this group of stars. His enormous tail, formed by a series of fairly bright stars, is easily recognizable from the shores of the Mediterranean Sea. The rest of the body, as well as the claws, is highly questionable and discussed. Although most tend to see the "trident " as the head and two claws of the scorpion, in this representation it has been chosen a different position. As I said at the entry about Ophiuchus, in fact, if we want to find the claws of the scorpion we must go to Libra.
About Libra we will talk later, now I just want to show you where are the claws of the scorpion. As you can see, the main shape of Libra is a "comet". The claws of the scorpion are, in fact, the two brightest stars in the constellation Libra, the one furthest to the right in the constellation Libra and the one further to the top. In this case, what once would have considered the two claws and the head is not more than the lower abdomen and the beginning of the tail.
Scorpius is a constellation, in my opinion, very impressive and it is unfortunate that in the northern hemisphere it just can be observed only in summer and, depending on the latitude where we are, may be partially hidden by the horizon. In Englad the tail is always hidden even when there are no elevation of the horizon, like mountains or a single tree. If you want to enjoy a magnificent view of the full constellation I recommend the beaches of Andalusia as it will always appear to the south and only from some Andalusian beaches you will have a totally clean and immaculate horizon and the whole constellation in the sky.
I know I promised also discuss myths associated with the constellations, but in this case, Scorpio is part of the myth of Orion and, therefore, be included when talking about it.
Let's go, finally, to Antares.
Antares is the brightest star in the constellation Scorpius. His position, marked in this figure, coincides with the beginning of the tail (assuming that the claws of the scorpion are in Libra). It has a magnitude of 1.05 making it even brighter than Polaris. Its color (B-V 1.86), and here's what makes this star so striking, is noticeably red. It's so red and so bright that is commonly confused with the planet Mars.
Moreover, his name, "Antares", is actually a derivation of Anti-Ares, "not-Ares". I note that both Mars to Romans and Ares to the Greeks represent the same divinity. Therefore, the planet we call Mars was called Ares by the Greeks and Antares was remembered as that red star that was not to be confused with Ares.
The last point I want to explain what it means that, in this case, is the last line in the description of the star. The coordinates of the star given as right ascension (RA) and declination (DE). These coordinates work the same way that the coordinates of latitude and longitude.
For the surface of the Earth, the latitude is 0 degrees at the equator and progresses to 90 degrees at the North Pole and -90 degrees at the South Pole. Moreover, the longitude is 0 degrees in the meridian of Greenwich and is progressing in an easterly direction. So, what is the west of the meridian of Greenwich have negative longitude (although it may be represented as a longitude greater than 180 degrees).
In the celestial sphere we saw that we also have a north pole and, therefore, a south pole and equator. Thus, the declination (DE) would be equivalent to the latitude and is represented in the same way, 0 degrees at equator, 90 degrees at the North Pole (near Polaris) and -90 degrees at the South Pole.
Right ascension (RA) is equivalent to the longitude, but in this case, is not represented in degrees but in hours, minutes and seconds and the start point is the vernal equinox, which actually is not a meridian, but a point also belong to the equator, specifically, one of the two points where the ecliptic intersects the celestial sphere equator. Right ascension also grows to the east.
Because of precession, the stars change position over time so, as reference, it is often taken the position of the stars in a given year. That is what is the value J2000, it means "the position of the stars in 2000".
Finally, I let you an enlarged picture of the area you can find Antares, showing the equatorial grid.
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