Crater (constellation)

Crater is a small constellation located in the southern part of the sky. Its name comes from the Latin word for a cup, which was used in ancient times to mix water with wine. This constellation was one of the 48 constellations described by the astronomer Ptolemy over 1,800 years ago. It shows the shape of a cup and is placed on the back of another constellation called Hydra, which looks like a water snake.

The stars in Crater are not very bright. The two brightest stars, Delta Crateris and Alpha Crateris, are older orange stars that are bigger and cooler than our Sun. Another star, Beta Crateris, is actually two stars orbiting each other—one a large white star and the other a very small, dense star. Scientists have found planets around seven different star systems in this area of the sky. There are also some interesting objects like galaxies and a very distant, bright object called a quasar in the Crater constellation.

Mythology

In old Babylonian star charts from around 1100 BC, the stars of Crater were sometimes grouped with the stars of the crow, called Corvus. Some believe these stars, along with the water snake Hydra, were symbols linked to the idea of the underworld.

In Greek stories, Crater is told through a myth about a crow that served the god Apollo. The crow was sent to fetch water but stopped to eat figs until they were ripe. When it finally returned with the water in a cup, it blamed a water snake for drinking some of it. Apollo saw through this trick and placed the crow, the cup, and the snake in the sky, arranging them so the crow could never drink from the cup. This tells a lesson about not disobeying the gods.

In Chinese astronomy, the stars of Crater are part of the Vermillion Bird of the South. They represent the bird's wings or a heroic bowman. In the Society Islands, Crater was known as a constellation called Moana-'ohu-noa-'ei-ha'a-moe-hara, meaning "vortex-ocean-in-which-to-lose-crime."

Characteristics

The Crater constellation covers 282.4 square degrees of the sky, making it the 53rd largest out of 88 constellations. It is bordered by Leo, Virgo, Corvus, Hydra, and Sextans. In 1922, the International Astronomical Union gave it the three-letter abbreviation "Crt". The borders of Crater were set in 1930 by Belgian astronomer Eugène Delporte and are shaped like a six-sided polygon.

In the equatorial coordinate system, Crater’s right ascension runs from 10^h 51^m 14^s to 11^h 56^m 24^s, and its declination ranges from −6.66° to −25.20°. Because it lies in the southern celestial hemisphere, the whole constellation can be seen by anyone living south of 65°N.

Features

Stars

Main article: List of stars in Crater

Johann Bayer, a German mapmaker, used Greek letters to name the brightest stars in this group of stars. Another mapmaker named Bode added a few more, but only one of these, called Psi Crateris, is still used today. John Flamsteed named 31 stars in Crater and part of a nearby group of stars called Hydra. Most of these stars are actually in Hydra.

The three brightest stars in Crater—Delta, Alpha, and Gamma Crateris—form a triangle near a brighter star in Hydra called Nu Hydrae. Delta Crateris is the brightest star in Crater. It is an orange star that is about 163 light-years away from us. Alpha Crateris, also an orange star, marks the base of the cup shape and is about 141 light-years away. Beta Crateris is a pair of stars orbiting each other, one being a white star and the other a tiny, dense star called a white dwarf.

Epsilon and Zeta Crateris mark the edge of the cup. Epsilon Crateris is a large, bright star about 366 light-years away. Zeta Crateris is also a pair of stars, with the bigger one shining brightly and the smaller one much dimmer. These stars are about 326 light-years from us.

Some stars in Crater change in brightness and are favorite targets for stargazers. R Crateris is a red star that dims and brightens over many days. TT Crateris is a system of stars where one pulls material from the other, causing bright flashes of light.

There are also interesting star systems like HD 98800, which is a group of four stars with a disk of dust and gas around them, and HD 96167, a star with a planet orbiting it.

Deep-sky objects

Crater 2 is a small galaxy that orbits our Milky Way galaxy, located about 380,000 light-years away. NGC 3511 is a spiral galaxy that looks almost like our own, and NGC 3513 is a barred spiral galaxy. NGC 3981 is another spiral galaxy with unusual arms.

RX J1131 is a very distant object called a quasar, where a giant black hole is at the center. In 2001, a powerful flash of light called a gamma-ray burst was detected and lasted for several minutes.

Meteor showers

The Eta Craterids is a meteor shower that happens between January 11 and 22, with the most meteors seen around January 16 and 17, near the star Eta Crateris.