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Key Facts & Information

  • Alphecca (α Coronae Borealis) is an eclipsing binary star found in the constellation of Corona Borealis. It is composed of two main-sequence stars and is located around 75 light years away from the Sun. Alphecca is also one of the magical Behenian fixed stars and is the brightest star in its constellation, the Corona Borealis. The star system’s apparent magnitude is 2.23 but its eclipsing stars cause brightness variations from 2.21 to 2.23 magnitude. The absolute magnitude varies from an estimation of 0.16 to 5.05.
  • Alphecca is noted to convey honor, dignity and artistic ability.
  • However, like all Venusian stars, it can also have negative effects.
  • Medieval astrologers asserted that Alphecca rising indicates a life spent in a variety of pleasurable pursuits by  someone who decked his body with adornments, secretly engaged in love affairs or adultery.
  • Main-sequence stars are characterized by the source of their energy, in which they fuse hydrogen atoms into helium atoms inside their cores.
  • Alphecca A, the primary star, is a white main-sequence star with a  spectral type A0V.
  • On the other hand, Alphecca B, the secondary star, is a yellow main-sequence star with a spectral type G5V.

Nomenclature

  • Throughout the ages, Alphecca bore a lot of names granted upon it by different cultures. It had traditional names such as Gemma, Gnosia, and Asteroth.
  • Alphecca is Arabic, and is short for “the bright star of the broken ring of stars”.
  • Gemma is Latin means “jewel”, and the constellation is known as the Northern crown.
  • Gnosio is also Latin which is short for “star of the crown of Knossos”.
  • Asteroth is Hebrew and translates as “Astarte”, a Middle Eastern goddess and also means “idols”.
  • The International Astronomical Union Working Group on Star Names (WGSN) favored the traditional name Alphecca as the preferred formal name of the star.
  • The 15 Behenian stars are Alkaid, Regulus, Procyon, Sirius, Aldebaran, Capella, Pleiades, Angol, Deneb Algedi, Vega, Antares, Alphecca, Arcturus, Spica, and Gienah. These stars were considered to have magical attributes in medieval times and were associated with stars and other objects.
  • Alphecca was associated with Venus and Mercury, conveying honor, dignity, and both poetical and artistic ability.
  • The star was depicted as a crowned man. It gave chastity and the love and goodwill of men.
  • It was also associated with topaz, rosemary, trefoil, and ivy.
  • Alphecca is also said to rule the lowest vertebra of the spine in the human body.

Distance, Size, And Mass

  • ALPHECCA A
    • Alphecca A is enveloped by a circumstellar disk of dust similar to the one that envelopes the star Vega
    • The primary star dominates its companion from every aspect.
    • It has a solar mass of about 2.58 and a radius between 2.89 to 3.04 solar radii
    • It is also much hotter than its companion and our Sun, with an estimation of average temperature around 9,700 K.
    • It is 74 times brighter and 1.6 times hotter than the Sun.
    • Alphecca A is also a very fast spinner with a rotational velocity of 139 km/s.
    • Its fast rotation contributes to its material being blown off and resulting in the enveloping circumstellar disk.
    • The primary star has an estimated age of 314 million years.
  • ALPHECCA B
    • Alphecca B is way smaller with a solar mass of around 0.92 and a radius of around 0.9 solar radii.
    • It is very similar to our sun with an almost matching surface temperature of 5,800 K, just 22 K hotter than the Sun.
    • The secondary star also spins much more slowly with a velocity of at most 14 km/s.
    • It is also less luminous than the sun with only 0.81 solar luminosities. However, its X-ray’s luminosity is 30 times greater than the peak activity level of the Sun.
    • In 2006, a survey with the Infrared Astronomical Satellite (IRAS) revealed excess emission in the infrared, which indicates the presence of a debris disk around the primary star in which planets and protoplanetary systems may form.
    • In 2014, a study published that the disk has an estimated radius of 61 astronomical units.
    • Alphecca is the 67th brightest star in the night sky and is visible to the naked eye. Despite being the brightest in its constellation, it is only moderately bright compared to the brightest stars. It is located 75 light years away from our Sun

Formation

  • Alphecca is believed to have formed around 314 million years ago.
  • It is still unknown if the binary stars, Alphecca A and B, formed at the same time.
  • However, Alphecca has been associated as a member of the Ursa Major Moving Group of stars because of its age and motion through space.
  • These stars have a common origin, age, and motion as they are believed to have formed in the same molecular cloud about 300 million years ago.
  • Alphecca is believed to have formed in this previously open cluster when gravity pulled the swirling gas and dust of a molecular cloud together.

Corona Borealis Constellation

  • Corona borealis constellation is one of the smallest yet also one of the most recognizable constellations found in the northern hemisphere.
  • Aside from the crown of Ariadne, it is also said to represent a beggar’s bowl in the Arab tradition, and the den of the Great Bear for some native Americans.
  • It is visible to the north observers at 50°S.
  • It lies 20° above and left of Arcturus.
  • Alphecca marks the base of the crown in the constellation. It is also said to mark the loop or knot of the ribbon along fastened buds, flowers, or leaves of the wreath.
  • The treatise, the Almagest, would be used by medieval European and Islamic scholars as an astrological and astronomical canon for over a thousand years.
  • According to Ptolemy, like Venus and Mercury, it is said to give artistic ability, love of flowers, lassitude, and disillusionment, but to bring it native to a position of command.
  • The Northern Crown is one of the 48 constellations listed by the 2nd Greco-Roman astronomer Ptolemy.
  • It is also associated with the Hebrew Letter Daleth and the 4th tarot Trump, the Emperor.
  • Astronomer Alvidas considered it to be like Mars and Mercury, in which it gives honor, dignity, and poetical and artistic ability.
  • It is also one of the 58 bright stars with a special status in the field of celestial navigation. It is part of the 13 navigational stars found in the equatorial region of the western celestial hemisphere together with Antares, Enif, Markab, Altair, Rasalhague, Sabil, Spica, and Nunki.

Alphecca in the Future

  • It is quite possible that Alphecca will leave its crown asterism in the far future since it has its own movement throughout the space.
  • Its association with the Ursa Major Moving Group also supports this possibility.
  • For now, both stars are stable and will remain stable for many years.
  • Alphecca A’s circumstellar disk may be a favorable place for a planet to be born.
  • The 10 brightest stars in the constellation Corona Borealis are Alphecca, Nusakan, Gamma Coronae Borealis, Theta Coronae Borealis, Epsilon Coronae Borealis, Delta Coronae Borealis, Zeta Coronae Borealis, Tau Coronae Borealis, Kappa Coronae Borealis, and Xi Coronae Borealis.

Did You Know?

  • Like the star Algol in the constellation Perseus, it is an eclipsing binary, with an orbital period of 17.36 days and an eccentricity of 0.37.
  • An eclipsing binary’s period of orbit may be determined by its light curve.
  • In these days, the fainter star of Alphecca passes in front of the brighter one, resulting a slight dip in brightness.
  • The star’s variation in brightness is barely perceptible.
  • Alphecca’s orbit is inclined at an angle of about 88.2° at our line of sight.
  • It is the only navigational star in the constellation Corona Borealis.
  • The average distance between the primary and secondary stars is 0.2 astronomical units.
  • During their orbit, the distance between the two stars can vary from 0.13 to 0.27 astronomical units.
  • The famous Pleiades star cluster sits almost opposite Alphecca in the sky.
  • In mid-November, Alphecca and Pleiades switch places in the sky after 12 hours.
  • Alphecca shines almost all night long in April, May, and June.
  • Alphecca A is much brighter and hotter than our own Sun.
  • The Ursa Major Moving Group includes most of the bright stars of the Big Dipper, namely, Alioth, Mizar, Alcor, Phecda, Merak and Megrez. It also includes some stars from other constellations: Menkalinan, Auriga.
  • The Chinese knew Alphecca as the Fourth Star of Coiled Thong, an asterism formed by Alpha, Pi, Theta, Beta, Gamma, Delta, Epsilon, Iota, and Rho Coronae Borealis.
  • The 17th century German astronomer Bayer claims that the Arabs knew Alphecca as Pupilla.