Epsilon Canis Majoris

Epsilon Canis Majoris, or Adhara, is a binary star system in Canis Major about 430 light-years from Earth. Its brighter component is a blue-white giant and one of the night sky’s brightest stars.

Adhara: Adhara is the traditional name for Epsilon Canis Majoris, a bright star system in Canis Major. This is the proper name most often used for the system.
Orbital mechanics: Orbital mechanics describes the motion of bodies under gravity, including stars moving around a shared center of mass. It explains how the two stars in Adhara remain bound.
Celestial navigation: Celestial navigation determines position or direction by observing celestial objects. Adhara’s brightness makes it a recognizable southern-sky reference star.
Sirius: Sirius is the brightest star in Earth’s night sky and the primary of a binary system in Canis Major. It outshines Adhara in the same constellation and provides a familiar comparison.
Blue giant: A blue giant is a hot, luminous star whose spectral type is generally O or B. Adhara’s primary is a hot, luminous B-type giant.
Spectroscopic binary: A spectroscopic binary is a binary star identified through periodic shifts in its spectral lines. Radial-velocity measurements are used to study Adhara’s close companion.
Ozone layer: The ozone layer is the region of Earth’s stratosphere with elevated ozone concentrations that absorbs much ultraviolet radiation. Adhara’s ultraviolet output may have affected Earth’s ancient upper atmosphere.
Wezen: Wezen, or Delta Canis Majoris, is a yellow-white supergiant star in Canis Major. It is another prominent member of Adhara’s constellation, but cooler and more evolved.
Binary star: A binary star is a system of two stars bound together by gravity and orbiting a shared center of mass. Adhara consists of two gravitationally bound stellar components.
Stellar wind: A stellar wind is a continuous outflow of charged particles from a star’s atmosphere. Adhara’s hot primary drives a strong outflow into surrounding space.

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