1. Introduction

Corvus, a constellation in the southern celestial hemisphere, derives its name from the Latin word for "crow" or "raven." Spanning a modest 184 square degrees of the night sky, Corvus is situated between the constellations Hydra and Virgo. Its distinct shape is formed by four primary stars that outline the silhouette of a celestial crow, making it easily recognizable to observers. The celestial coordinates of Corvus place it in the region of the sky with right ascension ranging from approximately 11h 56m to 12h 56m and declination falling between -11.5° and -25.5°. Positioned along the ecliptic path, Corvus is observable from latitudes in the southern hemisphere and lower latitudes in the northern hemisphere during certain times of the year (Figure 1).

Corvus is characterized by its four principal stars: Alchiba (α Corvi), Kraz (β Corvi), Minkar (ε Corvi), and Gienah (γ Corvi). Alchiba, often recognized as the "Alpha Star" in Corvus, serves as the southernmost point in the constellation. These stars collectively form an asterism resembling a crow in flight, providing an interesting visual aspect to the night sky.

In ancient mythology, Corvus is associated with various cultural narratives. In Greek mythology, the crow is linked to the god Apollo, symbolizing his trustworthiness as a messenger. The constellation is also part of the Greek story of Apollo's sacred bird, which failed to deliver a message and was consequently placed in the sky with a water snake (Hydra) and a cup (Crater).

Figure 1. IAU chart of Corvus. Source: https://www.iau.org/static/archives/images/screen/crv.jpg. Credit: IAU and Sky & Telescope. Reproduced under CC BY 4.0 license.

2. Historical Background and Mythology

In Greek mythology, Corvus is associated with several stories, one of the most prominent being its involvement in the myth of Apollo and Coronis. According to legend, Coronis was a mortal woman who caught the eye of Apollo, the god of the sun, light, and music. Coronis, however, betrayed Apollo by falling in love with a mortal man named Ischys. When Apollo learned of Coronis's infidelity, he sent a white crow to spy on her. The crow returned with the news of Coronis's betrayal, prompting Apollo to punish both Coronis and Ischys. In some versions of the myth, Apollo's anger was directed not only at Coronis but also at the crow for being too slow to deliver the message, turning its feathers from white to black and condemning it to eternal thirst by placing it in the sky with the constellation Hydra, the Water Snake.

Another Greek myth involving Corvus is the story of Apollo and the Raven. According to this legend, the crow was initially a pure white bird. Apollo, impressed by the crow's beauty and singing ability, decided to gift it with the ability to speak human language. However, the crow's newfound talent led to arrogance and vanity, and it boasted to Apollo that it was a better musician than the god himself. Apollo, angered by the crow's hubris, transformed its feathers from white to black and cast it into the sky as the constellation Corvus, as a lesson in humility.

In addition to Greek mythology, the crow holds significance in other cultures as well. In Norse mythology, Odin, the chief of the gods, was often accompanied by two ravens named Huginn and Muninn, meaning "thought" and "memory" respectively. These ravens served as Odin's messengers, flying across the world to gather information for him. The presence of the crow in various mythologies underscores its symbolic importance as a creature associated with intelligence, wisdom, and communication.

Throughout history, the constellation Corvus has been observed and referenced by different civilizations. Its distinct shape and association with ancient myths have contributed to its enduring significance in human culture. Today, Corvus remains a captivating sight in the night sky, serving as a celestial reminder of the timeless stories and symbols that have shaped human understanding of the cosmos.

3. Notable Stars

Alchiba (α Corvi): Alchiba, also known as Alpha Corvi, is the brightest star in the constellation Corvus. It is a binary star system composed of two main-sequence stars. The primary star is a yellow-white dwarf of spectral type A0V, while the secondary star is a fainter companion. Alchiba has an apparent magnitude of approximately 4.00 and is located around 49 light-years away from Earth.

Kraz (β Corvi): Kraz, or Beta Corvi, is another notable star in Corvus. It is a binary star system consisting of a primary star and a fainter companion. The primary star is a blue-white dwarf of spectral type B8V, while the secondary star is a close companion. Kraz has an apparent magnitude of approximately 2.65 and is situated approximately 140 light-years away from Earth.

Minkar (ε Corvi): Minkar, also known as Epsilon Corvi, is a binary star system located in Corvus. The primary star is a yellow-white dwarf of spectral type F0V, while the secondary star is a fainter companion. Minkar has an apparent magnitude of approximately 3.01 and is located around 303 light-years away from Earth.

Gienah (γ Corvi): Gienah, or Gamma Corvi, is a binary star system in Corvus. The primary star is a blue-white subgiant of spectral type B8IV, while the secondary star is a fainter companion. Gienah has an apparent magnitude of approximately 2.59 and is situated approximately 163 light-years away from Earth.

Delta Corvi (δ Corvi): It is a binary star system consisting of two stars orbiting around their common center of mass. Delta Corvi is also known by its traditional name, Algorab. The primary component, Delta Corvi A, is a blue-white main-sequence star of spectral type A0V. It shines with an apparent magnitude of approximately 2.95, making it one of the brighter stars in the constellation Corvus. This star is relatively young and hot, with a surface temperature exceeding 9,000 Kelvin. The secondary component, Delta Corvi B, is a fainter star that orbits around Delta Corvi A. It is a spectral type A7V star, indicating that it is also a main-sequence star, albeit slightly cooler and less luminous than its companion. The orbital period of the Delta Corvi binary system is approximately 5.2 years, with an average separation between the two stars of about 1.5 astronomical units (AU).

4. Deep-Sky Objects

NGC 4038 and NGC 4039 (The Antennae Galaxies): Located near the border of Corvus and Hydra, the Antennae Galaxies are a pair of interacting galaxies undergoing a dramatic collision. This collision has triggered intense star formation and resulted in the formation of long tidal tails resembling antennae, hence their name. The Antennae Galaxies are a prominent target for astronomers studying galactic mergers and their effects on star formation.

NGC 4361: NGC 4361 is a planetary nebula situated in the southern part of Corvus. It is notable for its intricate structure, which includes a central star surrounded by a glowing shell of gas and dust ejected during the star's late stages of evolution.