Crater
“The Cup” · Southern · best around April evenings
Real star positions and magnitudes (HYG database via D3-Celestial, BSD-3). Lines are the conventional stick figure; north is up.
The story
Apollo's goblet, balanced on the sea-serpent Hydra's back — a faint but ancient constellation.
How to find it
The dim goblet between Corvus and Leo.
✦ What lives inside it
The deep dive
Researched for the Atlas from Wikipedia — Crater (constellation) (11,752 characters read) · updated Sep 20, 2026
01 A cup with no bright stars to pour
Crater is one of those constellations that tests a dark sky's quality rather than rewarding a casual glance. Not a single star within its borders reaches third magnitude — its brightest, Delta Crateris, scrapes in at magnitude 3.56, roughly the faintness you would expect from a moderately light-polluted suburb. For comparison, the dimmest star in the Big Dipper's handle is about magnitude 1.9. In total, Crater contains only 33 stars bright enough to be seen with the naked eye under good conditions, meaning apparent magnitude 6.5 or better. The constellation covers 282.4 square degrees of sky — 0.685% of the entire celestial sphere — and ranks 53rd in area among the 88 modern constellations. Its borders, formally defined by Belgian astronomer Eugène Delporte in 1930, form a six-sided polygon. The right ascension span runs from 10h 51m 14s to 11h 56m 24s, and declination from −6.66° to −25.20°, placing the cup firmly in the southern celestial hemisphere but still visible to anyone living north of latitude 65°N.
02 Delta and Alpha: the cup's aging orange giants Deeper
The two stars that dominate Crater are both orange giants in the twilight of their hydrogen-burning lives, and their physical statistics show just how dramatically stars swell as they age. Delta Crateris, the brighter of the two at magnitude 3.56, lies 163 light-years away and carries a mass only 1.0 to 1.4 times that of the Sun — yet it has ballooned to 22.44 solar radii. Stretched across 22 times the Sun's width, it would swallow Mercury and reach partway toward Venus if placed at our solar system's center. It radiates 171.4 times the Sun's power from an outer envelope cooled to 4,408 K, giving it that warm orange tint. Alpha Crateris — traditionally named Alkes, meaning "the cup" — marks the base of the vessel at magnitude 4.07, 141 light-years distant. It is more massive than Delta at an estimated 1.75 solar masses, has expanded to 13.2 solar diameters, shines with 69 solar luminosities, and runs slightly hotter at around 4,600 K. Both stars have used up the hydrogen fuel in their cores, leaving them swelling and cooling on their way to eventual red giant status.
03 Beta Crateris and its invisible companion Deeper
Beta Crateris presents one of the more intriguing stellar pairings in this region of sky. At magnitude 4.5, the system sits 296 light-years from the Sun and is officially classified as a binary consisting of a white-hued giant of spectral type A1III and a companion white dwarf catalogued as type DA1.4. White dwarfs are the dense, Earth-sized remnants of dead stars — this one was once a star in its own right, burned through its fuel, shed its outer layers, and collapsed. Despite being a confirmed member of the system, the white dwarf is so vastly outshone by the primary that it cannot be resolved as a separate object even with the Hubble Space Telescope. The pairing serves as a reminder that binary stars can hide radically different objects within a single point of light visible to the naked eye. Gamma Crateris offers a contrasting case: its double nature can be resolved with small amateur telescopes. Its primary is a white main-sequence star of spectral type A7V with an estimated mass 1.81 times that of the Sun, while the secondary, at magnitude 9.6, carries about 75% of a solar mass and is likely an orange dwarf. The two take at least 1,150 years to complete a single orbit around each other.
04 Epsilon Crateris: the cup's biggest naked-eye star
While Delta Crateris wins on brightness, Epsilon Crateris claims the title of the physically largest star in the constellation that can be seen without a telescope. Classified as a K5 III evolved giant, it has a mass similar to the Sun's but has expanded to an extraordinary 44.7 solar radii — more than twice as bloated as Delta. At that size it would engulf Venus's orbit if it replaced our own Sun. It radiates 391 times the solar luminosity and sits 366 light-years from Earth. Epsilon, along with Zeta Crateris, marks the rim of the mythological cup. Zeta is itself a binary system at 326 light-years, its primary a G8 III red clump star generating energy by fusing helium rather than hydrogen in its core — a brief but well-defined evolutionary phase. Zeta has expanded to 13 solar radii and shines with 157 solar luminosities. Remarkably, Zeta Crateris is a confirmed member of the Sirius supercluster and is also a candidate member of the Ursa Major Moving Group, a loose family of stars sharing similar trajectories through space that may once have formed together in the same open cluster.
05 Variable and cataclysmic stars for patient watchers
Crater hides several variable stars that reward patient monitoring. R Crateris, located near the star Alkes, is a semiregular variable of type SRb with a deep red spectral class of M7. It fluctuates between magnitudes 9.8 and 11.2 over a rough period of 160 days, sitting 770 light-years away. Far more dramatic is TT Crateris, a cataclysmic variable in which a white dwarf — roughly as massive as the Sun — orbits an orange dwarf of spectral type K5V so closely that the two complete a full circuit every 6 hours and 26 minutes. The white dwarf's gravity continuously strips matter from its companion, piling it onto an accretion disk that periodically ignites in a violent outburst. In its quiet state the system glows at magnitude 15.9, far beyond amateur equipment; during eruption it rockets to magnitude 12.7, suddenly becoming accessible. SZ Crateris offers a quieter contrast: a magnitude 8.5 BY Draconis variable lying only about 42.9 light-years away, making it one of the nearest star systems in the constellation. It too belongs to the Ursa Major Moving Group, linking it genetically to Zeta Crateris across a significant span of sky.
06 HD 98800: a quadruple nursery with a planet-forming disk Deeper
One of Crater's most scientifically remarkable objects is invisible to the naked eye yet extraordinary in structure. HD 98800, also catalogued as TV Crateris, is a quadruple star system estimated to be only 7 to 10 million years old — a cosmic infant at roughly 0.2% the age of our solar system. It consists of two pairs of stars, each pair orbiting its own partner closely, with the two pairs in turn orbiting each other. The system earned special attention because one of the stellar pairs hosts a debris disk of dust and gas stretching between 3 and 5 astronomical units from those stars, spanning a zone comparable to the asteroid belt out to Jupiter's orbit in our own solar system. Researchers interpret this disk as a protoplanetary disk — the raw material from which planets could form. Watching such a young system gives astronomers a live view of conditions similar to what our own solar system experienced billions of years ago. Equally exotic, though far more solitary, is the nearby brown dwarf DENIS-P J1058.7-1548, which has less than 5.5% of the Sun's mass and a surface temperature between 1,700 and 2,000 K — cool enough for clouds to condense. Brightness variations in both visible and infrared wavelengths suggest it has real atmospheric cloud cover, making it a miniature cloudy world in its own right.
07 Seven planetary systems hidden in the cup
Seven star systems within Crater's borders have been confirmed to host planets, giving this dim constellation an outsized planetary census. HD 96167 hosts a planet with at least 68% of Jupiter's mass that takes 498.9 days to orbit its slightly evolved yellow host star, but the orbit is strikingly elongated — the planet swings between 0.38 and 2.22 astronomical units from its star, a wild range that would carry it from inside Mercury's equivalent orbit out past Mars. HD 98649 takes the eccentricity extreme further: its companion, at least 6.8 times Jupiter's mass, has an orbit reaching as far as 10.6 astronomical units, putting it beyond Saturn's distance in our system and making it a candidate for eventual direct imaging — an achievement still rare in exoplanet science. At the other end of the scale, BD-10°3166 has a hot Jupiter with a minimum mass of 48% of Jupiter's that screams around its orange host star in just 3.49 days, while WASP-34's planet of 0.59 Jupiter masses completes its orbit in 4.317 days around a near-solar-twin star of spectral type G5V located 432 light-years away.
08 RX J1131: a quasar with a measured black hole spin
Among Crater's deep-sky inhabitants, the quasar RX J1131 stands in a class entirely its own. It lies approximately 6 billion light-years from the Sun — so remote that its light set out when the universe was less than half its current age — and yet it earned a unique entry in astrophysical history. The black hole at the quasar's heart was the first black hole anywhere in the universe to have its spin directly measured. Spin is one of only two fundamental properties a black hole can possess alongside mass, and pinning it down required using the gravitational lens formed by a foreground galaxy to magnify and analyze the quasar's X-ray emission in extraordinary detail. The constellation also recorded two notable gamma-ray bursts. GRB 011211, detected on December 11, 2001, blazed for 270 seconds — the longest burst that the X-ray satellite BeppoSAX had ever recorded at that time. GRB 030323, detected on March 23, 2003, lasted 26 seconds. Both events originated from cosmological distances, briefly outshining entire galaxies before fading.
09 Crater 2 and the Crater Cloud of galaxies
Crater is home to a dwarf galaxy with an oddly familiar address. Crater 2 is a satellite galaxy of our own Milky Way, orbiting approximately 380,000 light-years from the Sun — a distance comparable to the Moon's distance from Earth, scaled up by a factor of 1.5 billion. As dwarf satellite galaxies go, it is a member of the extended Milky Way family. The constellation also contains NGC 3511, a spiral galaxy seen nearly edge-on at magnitude 11.0, located about 2 degrees west of Beta Crateris, and NGC 3513, a barred spiral galaxy only 11 arcminutes away from it on the sky. More dramatically, NGC 3981 is a spiral with two wide, disturbed arms — signs of gravitational interaction — and belongs to the NGC 4038 Group. That group, together with NGC 3672 and NGC 3887, forms part of a larger structure called the Crater Cloud, a collection of 45 galaxies embedded within the vast Virgo Supercluster. This chain of membership — from individual galaxy to group to cloud to supercluster — illustrates how Crater, for all its faintness, sits at the intersection of structures spanning hundreds of millions of light-years.
10 Apollo's crow, a plague cup, and a Polynesian vortex
The mythology attached to Crater spans cultures separated by thousands of miles and radically different worldviews. In the dominant Greek tradition, the cup belongs to Apollo and is entangled with the punishment of a deceptive crow: sent to fetch water, the bird instead waited for figs to ripen, then brought back a water snake as a scapegoat for its tardiness. Apollo saw through the lie and hurled all three — crow, cup, and snake — into the sky as the constellations Corvus, Crater, and Hydra, arranged so the crow can never drink from the cup, a permanent warning against deceiving the gods. A darker Greek myth, recorded by Phylarchus, has nothing to do with Apollo. In that account, a plague struck the city of Eleusa near Troy, and a king named Demophon rigged a sacrificial lottery to spare his own daughters. A nobleman named Mastusius forced the issue, saw his daughter sacrificed, then killed Demophon's daughters in revenge and served the king a cup of their blood mixed with wine. When Demophon discovered the truth, he had Mastusius and the cup cast into the sea — and Crater commemorates that cup. The Society Islands of Polynesia recognized the same stars as a constellation named Moana-'ohu-noa-'ei-ha'a-moe-hara, translating roughly as "vortex-ocean-in-which-to-lose-crime" — a remarkably parallel theme of guilt and watery disposal.
11 Babylonian gates and Mithraic icons Deeper
Long before Greek astronomers codified the cup, Babylonian sky-watchers had incorporated what we now call Crater into their own celestial map. In cuneiform star catalogues dating to at least 1100 BC, the stars of Crater were possibly merged with those of Corvus into a single figure called the Babylonian Raven, written in cuneiform as MULUGAMUSHEN. British scientist John H. Rogers, studying these ancient catalogues, noted that the neighboring constellation Hydra was identified with Ningishzida, the Babylonian god of the underworld, in the astronomical compendium known as MUL.APIN. From this, Rogers proposed that Corvus and Crater — riding together on the back of the water snake — functioned collectively as symbols of death and marked the symbolic gate to the underworld in Babylonian cosmology. The same grouping of cup and crow also appeared in the iconography of Mithraism, the mystery cult believed to have originated in the Middle East before spreading through the Roman Empire. The persistence of this cup-and-bird pairing across Babylonian, Mithraic, and Greek traditions suggests the grouping may carry a very ancient symbolic resonance, though the precise lines of cultural transmission remain debated.
12 Chinese wings, a lunar mansion, and a heroic archer
In the Chinese astronomical tradition, the stars of Crater do not form a cup at all. They fall within the vast asterism of the Vermillion Bird of the South, one of the four great celestial palaces that divide the Chinese sky. Specifically, Crater's stars — combined with some stars from neighboring Hydra — form Yi, representing the wings of the Red Bird. Yi carries a double significance: it also designates the 27th lunar mansion, one of the 28 divisions of the sky used to track the Moon's monthly journey in East Asian astronomy. In an alternative reading within the same tradition, Yi shifts its meaning entirely, depicting not a bird's wings but a heroic bowman, with his bow drawn from other stars in Hydra. The flexibility of that interpretation — the same stars simultaneously a wing and an archer — reflects how Chinese asterisms were layered with multiple meanings rather than fixed to a single image. Together with the Babylonian, Greek, and Polynesian traditions, the Chinese readings of Crater's stars underscore that this modest patch of southern sky has been a canvas for human imagination across an extraordinary range of cultures, each finding a different story inscribed in its faint points of light.
13 Bayer, Flamsteed, and how the cup was labeled Deeper
The process of assigning systematic names to Crater's stars unfolded across two centuries of European cartography. The German cartographer Johann Bayer, whose 1603 star atlas Uranometria introduced the Greek-letter labeling system still in use today, assigned letters alpha through lambda to Crater's most prominent stars. Later, the astronomer Johann Elert Bode added further designations, though of his additions only Psi Crateris survived into modern usage. John Flamsteed, the first Astronomer Royal of England, took a different approach: he assigned numbered designations to 31 stars covering both Crater and the stretch of Hydra immediately beneath it, treating them together as a single region he called Hydra et Crater. Most of those 31 numbered stars actually fall within Hydra rather than Crater proper, illustrating how constellation boundaries were fluid and contested before Eugène Delporte formalized them in 1930 on behalf of the International Astronomical Union. The IAU had already standardized the three-letter abbreviation "Crt" for Crater in 1922. The result of this layered history is that Crater's stars carry labels from at least three different naming traditions, a common feature of constellations that passed through the hands of many observers before modern astronomy imposed order on the sky.