Cappella

Capella (Alpha Aurigae / α Aur / 13 Aurigae) is the name of the brightest star in the constellation Auriga, ("The Coachman"), and the sixth brightest in the sky. It is the closest first magnitude star to the North Celestial Pole. It is 42.2 light years away from the Sun.

Name

Its name comes from the Latin capella, “little goat”, and is the origin of the Roman myth of the goat Amalthea who nursed Zeus. It also receives the Arabic names of Alhajoth, which also means "The Goat", and Al Rakib, "The Driver", because at sunset and twilight it was the The first star that was seen among all those that surrounded it. In ancient Akkadian it was called Dil-gan I-ku, the "Messenger of Light", as well as Dil-gan Babill, the "Honorary Star of Babylon". ». Some Celtic temples have been discovered that were oriented in such a way that they received the first Capella ray when it came out. Ancient observers attributed a reddish coloration to it, completely inexplicable.

In Hindu mythology, Capella was Brahma Ridaya, symbolizing the heart of Brahmā.

Star System

Although Capella is a quadruple star, its double star status was first recognized through spectroscopic studies and then (in 1919) with interferometry. The visual separation of these components, A and B, does not exceed 0.05 arcseconds, corresponding to a real separation of 0.73 astronomical units (au). They move along a nearly circular orbit with an orbital period of 104 days.

12 arcminutes from A+B are two fainter companions, named C and D, which lie 11,000 au (0.17 light-years) from the main pair, orbiting so enormous that they have not yet been has been able to complete through observations; a first approximation estimate for this orbit yields a period of about 400 years. The average separation between C and D is about 48.1 au.

The model offered by Capella can be assimilated to two spheres of 35 and 20 cm in diameter separated 3 m from each other; Two 2 cm spheres would be located 40 km from the main couple, separated by 120 m.

The system is part of the Hyades current.

Physical characteristics

The two main stars in the system, Capella A and Capella B, are yellow giant stars with surface temperatures similar to that of the Sun; their sizes, however, are much larger than this one. The combined light of this pair is what causes, when observed with the naked eye at night, the intense yellow color of Capella.

Comparative sizes of the four Capella and Sun components.

Capella A, of spectral type G8IIIe, has a radius 12.2 times greater than the solar radius and a mass of 2.7 solar masses. With a luminosity 78.5 times greater than that of the Sun, its age is estimated at about 525 million years. The low abundance of lithium on its surface indicates that nuclear fusion of helium into carbon has begun in its core. It is also a variable star of type RS Canum Venaticorum.

Capella B, of spectral type G1III, has a radius of 9 solar radii, a mass of 2.6 solar masses, and a luminosity 77.6 times that of the Sun. rotation is much greater than that of Capella A, so its chromospheric activity is greater. It is thought that it is less evolved than its companion and that the transformation of helium into carbon has not yet begun in its nucleus. However, both stars are now in the process of expanding and cooling on their way to becoming red giants, which will take a few million years.

Capella C and Capella D are two red dwarfs of magnitudes 10 and 12 respectively. Capella C has spectral type M1V and, with a radius of 58% of the solar radius, its luminosity is only 1.3% that of the Sun. Capella D, of type M4-5V, it is even smaller and dimmer, with a luminosity that barely reaches 0.05% that of the Sun.

History of your observation

Capella was the brightest star in the night sky from 210,000 years ago to 160,000 years ago, with an apparent magnitude of about -1.8. At -1.1, Aldebaran was the brightest before this period; it and Capella were located quite close to each other in the sky and approximated the northern pole stars of the time.

Cappella is believed to be mentioned in an Akkadian inscription from the 20th century BCE. C. Its symbolism associated with the goat dates back to Mesopotamia as a constellation called "GAM", "Gamlum" or "MUL.GAM" in the MUL.APIN document of the VII century a. C. GAM represented a scimitar or a staff and could represent the star alone or the constellation Auriga as a whole. Later, Bedouin astronomers created constellations that were groups of animals, where each star represented an animal. The Charioteer's stars formed a herd of goats, an association also present in Greek mythology. It is sometimes referred to as the Shepherd's Star in English literature[39]. Capella was considered an omen of rain in classical times.

Building J (first floor) of Monte Alban.

Building J of the pre-Columbian site of Monte Albán, in the state of Oaxaca (Mexico), was built around the year 275 BC. C., with a different orientation to that of other structures in the complex. Its steps are aligned perpendicular to the rise of Capella at that time, so that a person leaning out of a door of the building would have looked directly at it. Capella is important because its heliacal rise occurred one day after the Sun passed directly over Monte Albán.