Adhara (ε Canis Majoris) Worksheets

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Key Facts & Information

  • Adhara is the 22nd brightest star in the night sky and the 2nd brightest star in the constellation of Canis Major.
  • This star is a binary star system which is called Epsilon Canis Majoris. It is the brightest known source of ultraviolet in the sky.
  • The constellation of Canis Major, known as the Great Dog, is home to Sirius, brightest star in the night sky, and Adhara, which was once the brightest star. It reached the climax of visual magnitude that no other star will ever reach again for many years.
  • Adhara comes from an Arabic phrase “Al Ahadra”. It is sometimes spelled as Adara which translates to “the Maidens” of “the Virgins”.
  • It is a binary star consisting of Epsilon Canis Majoris A, a bright giant which appears bluish-white in color, and a spectral type of B2 II. It has a companion star, which is designated as Epsilon Canis Majoris B.
  • Adhara is located at around 430 light-years / 132 parsecs away from the Sun. It is quite young estimatedly to be around 22.5 million years old.

Formation

  • The Adhara star system was formed roughly 22.5 million years ago. It is unknown if both the stars were formed at the same time. Like the other stars, Adhara was formed either by a molecular cloud or nebula of gas and dust.
  • Gravity pulled the swirling gas and dust together and gave birth to the greatest source of ultraviolet wavelengths in the shape of the star. It is certain that this star took shape much closer to us than in the distant past.
  • At around 4.7 million years ago, Adhara was only 34 light-years away from us. It was also the brightest star in the sky with the greatest magnitude ever recorded, which was 3.99. It is much younger than the Sun, which is 4.603 billion years old.

Distance, Size & Mass

  • Adhara is located at around 430 light-years / 132 parsecs away from the Sun.
  • The primary star is almost 14 times bigger than our Sun. It has an estimated 12.6 solar masses and 13.9 solar radii. The characteristics of the companion star with regards to its size/mass is currently unknown.

Other Characteristics

  • Adhara is a binary star consisting of Epsilon Canis Majoris A, a bright giant which appears bluish-white in color, and a spectral type of B2 II. It has a companion star, which is designated as Epsilon Canis Majoris B.
  • Epsilon Canis Majoris A has an apparent magnitude of 1.50 and an absolute magnitude of -4.8. It has a temperature of 22,900 K, which makes it 4 times hotter than the Sun. Epsilon Canis Majoris B has an absolute magnitude of 1.9 and an apparent magnitude of 7.5.
  • The primary star is the brightest known extreme ultraviolet source in the night sky, which is 38,700 times the Sun’s brightness. Epsilon Canis Majoris B is estimated to be 250 times fainter than Epsilon Canis Majoris A.
  • Epsilon Canis Majoris A has a rotational velocity of around 25 km / 15.5 mi per second. It is used to determine the ionization state of the Local Interstellar Cloud because it is the strongest source of photons capable of ionizing hydrogen atoms in interstellar gas. This interstellar cloud is 30 light-years across and the Sun is traveling through it.

Other Characteristics

  • Epsilon Canis Majoris A is separated by about 7.5 arcseconds / 900 AU from its companion star, Epsilon Canis Majoris B.
  • Based upon these calculations, the companion star completes one orbit around the primary in at least 7,500 years.

Location

  • Adhara is located in the constellation of Canis Major. It represents one of the two great dogs who follow Orion, the celestial hunter. It marks one of the hind legs of Canis Major.
  • This constellation is home to Sirius, the brightest star in the night sky, and VY Canis Majoris, one of the largest known stars.
  • There are also other interesting stars and deep-sky objects. The best time to view them is every February. One of the closest dwarf galaxies to Earth, Canis Major Dwarf, is also located in this constellation.

The Future

  • Adhara is a likely candidate for a supernova explosion in the future.
  • Though the star reached an impressive -3.99 visual magnitude 4.7 million years ago, this will happen again in around 5 million years from now, when another star will reach this brightness and possibly even surpass it.
  • One of the stars which came close to this statistic was Adhara’s neighbor Mirzam, it had an apparent magnitude of -3.65 around 4 million years ago.

Did You Know?

  • If Adhara was placed in the position of Sirius, it would be 15 times brighter than the planet Venus in the night sky.
  • Some sources claim that Adhara is on the border between the first and second magnitude. While others claim that it is the faintest first-magnitude star, others say that it is the second- brightest, second-magnitude star.
  • For the Chinese, Adhara is known as the Seventh Star of Bow and Arrow. It is an asterism formed by Adhara, Wezen, Aludra, Kappa Canis Majoris, c Puppis, Chi Puppis, Omicron Puppis, k Puppis, and Pi Puppis.
  • In the 17th century, an Egyptian astronomer designated Adhara as the star Aoul al Adzari, which means “the first of the virgins” in his Candelarium.
  • “Aoul al Adzari” was later on translated into Latin as Prima Virginum, which means “the other virgins”. The stars comprising this are Wezen, Aludra, and Omicron Canis Majoris.
  • Adhara and Sirius are part of the 58 stars selected for navigation. They have been included in the list of navigational stars because of their brightness. It is also because of they are easily recognizable.
  • The flag of Brazil features 27 stars with each and everyone of them symbolizing a Brazilian Federative Unit. Adhara is one of these stars and it represents the state of Tocantins.