1. Introduction

Crater, the Latin term for "cup" or "bowl," is a constellation residing in the southern celestial hemisphere. Occupying a relatively small area of the night sky, Crater is situated adjacent to the sprawling constellation Hydra. The celestial coordinates of Crater position it between approximately right ascension 11h 36m to 11h 56m and declination -10.5° to -25.5°. This places the constellation within the vicinity of the celestial equator, allowing observers from both hemispheres to catch a glimpse of its celestial wonders. Due to its southern location, Crater is more prominently visible from latitudes below the Tropic of Cancer (Figure 1).

Characterized by its modest size, Crater covers an area of about 282 square degrees in the night sky. Despite its relatively small stature, the constellation possesses several notable stars and deep-sky objects that captivate the attention of astronomers and stargazers alike. These celestial features, though not as prominent as those found in larger constellations, contribute to the charm and allure of Crater as a distinct region of the celestial sphere.

In cultural lore, Crater is often associated with various mythological tales, particularly in Greek mythology. One such narrative links Crater to the story of Apollo, the god of the sun, who was said to have been gifted a magnificent golden cup known as the "Cup of Apollo." This cup was believed to provide ambrosia, the divine food of the gods, and served as a symbol of prosperity and abundance.

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

2. Historical Background and Mythology

The constellation Crater, known as the "Cup" or "Bowl" in Latin, has a historical background and mythological significance that dates back to ancient times. It is one of the 48 constellations identified by the Greek astronomer Ptolemy in the 2nd century AD, but its origins can be traced even further back to ancient Mesopotamia and Egypt.

In Mesopotamian astronomy, Crater was associated with the Sumerian goddess Ninkasi, who was the goddess of beer and brewing. The constellation represented the brewing vat or the cup from which the beer was poured. Beer held great cultural and religious importance in ancient Mesopotamia, and Ninkasi was revered as the patron deity of brewing and fermentation. The presence of Crater in the night sky served as a celestial reminder of the importance of this beverage in ancient Mesopotamian society.

In ancient Egyptian astronomy, Crater was linked to the goddess Hathor, who was often depicted holding a cup or goblet symbolizing the milk of the heavens. Hathor was a multifaceted deity associated with fertility, motherhood, music, and joy. The constellation Crater represented the cup from which Hathor poured the nourishing milk of the gods, ensuring fertility, abundance, and prosperity on Earth. The association with Hathor further emphasized the symbolic significance of Crater as a vessel of divine blessings and sustenance.

In Greek mythology, Crater is associated with the story of Apollo, the god of the sun, light, music, and prophecy. According to myth, Apollo was often depicted carrying a golden cup or chalice, which was believed to contain the nectar of the gods. This cup, known as the "Cup of Apollo" or the "Cup of Hygieia," was said to provide eternal health and vitality to those who drank from it. The constellation Crater was identified as the celestial representation of this legendary cup associated with the god Apollo.

Another interpretation of Crater in Greek mythology is linked to the story of the hero Heracles (Hercules). In one of his twelve labors, Heracles was tasked with retrieving the golden apples of the Hesperides, which were guarded by the dragon Ladon. During his quest, Heracles encountered the titan Atlas, who offered to retrieve the apples for him if Heracles would hold up the heavens (represented by the celestial sphere) in his absence. Atlas retrieved the apples and returned, but Heracles tricked him into taking the heavens back by offering to hold them momentarily while he adjusted his cloak. Atlas took back the heavens, and Heracles seized the opportunity to flee with the apples. As a reward for his cunning, Heracles was granted the celestial cup (Crater) to commemorate his victory.

3. Notable Stars

Alkes (Alpha Crateris): Alkes, also known as Alpha Crateris, is the brightest star in the constellation Crater. It is a binary star system located approximately 174 light-years away from Earth. The primary component of Alkes is an orange giant star of spectral type K1III, with an apparent magnitude of about 4.08. The secondary component is a fainter star that orbits around the primary star. Alkes derives its name from the Arabic word for "the cup," reflecting its association with the cup-shaped constellation.

Labrum (Beta Crateris): Labrum, or Beta Crateris, is another notable star in the constellation. It is a binary star system located about 266 light-years away from Earth. The primary component is an orange giant star of spectral type K1III, with an apparent magnitude of approximately 4.46. The secondary component is a fainter star that orbits around the primary star. Labrum's name is derived from the Latin word for "lip" or "rim," symbolizing its position near the edge of the cup-shaped constellation.

Delta Crateris: Delta Crateris is a single star located in the constellation Crater. It is a white main-sequence star of spectral type A0V, with an apparent magnitude of around 3.56. Delta Crateris is approximately 183 light-years away from Earth. This star is notable for its brightness and its role in defining the shape of the constellation.

4. Deep-Sky Objects

NGC 3511: NGC 3511 is a barred spiral galaxy located in the constellation Crater. It is situated approximately 36 million light-years away from Earth. NGC 3511 exhibits distinctive spiral arms and a bright central bulge, characteristic of barred spiral galaxies. Observations of NGC 3511 provide astronomers with valuable insights into galactic structure and evolution.

NGC 3887: NGC 3887 is another spiral galaxy found within Crater. It is approximately 60 million light-years distant from Earth. NGC 3887 features prominent spiral arms and a bright nucleus, typical of spiral galaxies. Its appearance suggests ongoing star formation activity within its spiral arms. Studying NGC 3887 contributes to our understanding of galaxy formation and the processes driving star formation in the universe.

NGC 3981: NGC 3981 is a spiral galaxy located in the northern part of Crater. It is situated approximately 65 million light-years away from Earth. NGC 3981 exhibits a well-defined spiral structure with distinct arms and a bright central region. Observations of NGC 3981 provide astronomers with opportunities to study galactic dynamics and the interplay between stars, gas, and dust in spiral galaxies.

Crater 2, also known as Crater II, is a dwarf galaxy located in the constellation Crater. It is one of the many satellite galaxies orbiting the Milky Way and is classified as a dwarf spheroidal galaxy. Crater 2 was discovered in 2016 through data obtained from the Dark Energy Survey, a project aimed at mapping distant galaxies and dark matter in the universe.