Crater is a small constellation in the southern celestial hemisphere. Its name is the latinization of the Greek krater, a type of cup used to water down wine. One of the 48 constellations listed by the second-century astronomer Ptolemy, it depicts a cup that has been associated with the god Apollo and is perched on the back of Hydra the water snake.
Hydra is the largest of the 88 modern constellations, measuring 1303 square degrees, and also the longest at over 100 degrees. Its southern end abuts Libra and Centaurus and its northern end borders Cancer. It was included among the 48 constellations listed by the 2nd century astronomer Ptolemy. It is commonly represented as a water snake. It is located in the southern hemisphere. It should not be confused with the similarly named constellation of Hydrus.
Alpha Crateris, officially named Alkes, is a star in the constellation of Crater. It is a cool giant star about 43.2 parsecs (141 ly) away.
Sigma Hydrae, also named Minchir, is a solitary star in the equatorial constellation of Hydra. It is visible to the naked eye with an apparent visual magnitude of 4.48. The estimated distance to this star from the Sun, based upon an annual parallax shift of 8.75 mas, is around 370 light-years. At that distance, the visual magnitude of the star is diminished by an interstellar extinction factor of 0.16, due to intervening dust.
TW Hydrae is a T Tauri star approximately 196 light-years away in the constellation of Hydra. The star is the closest such star to the Solar System. TW Hydrae is about 80% of the mass of the Sun, but is only about 5-10 million years old. The star appears to be accreting from a face-on protoplanetary disk of dust and gas, which has been resolved in images from the ALMA observatory. TW Hydrae is accompanied by about twenty other low-mass stars with similar ages and spatial motions, comprising the "TW Hydrae association" or TWA, one of the closest regions of recent "fossil" star-formation to the Sun.
Epsilon Hydrae is a multiple star system of a combined third magnitude in the constellation of Hydra. Based upon parallax measurements obtained during the Hipparcos mission, it is located roughly 129 light-years distant from the Sun.
Nu Hydrae, Latinized from ν Hydrae, is an orange-hued star in the constellation Hydra, near the border with the neighboring constellation of Crater. It has an apparent visual magnitude of 3.115, which is bright enough to be seen with the naked eye. Based upon parallax measurements, this star is located at a distance of about 144 light-years from the Earth.
Beta Crateris, Latinized from β Crateris, is a binary star system in the southern constellation of Crater. It is visible to the naked eye with an apparent visual magnitude of 4.46. Based upon an annual parallax shift of 9.59 mas as seen from Earth, it is located around 340 light years from the Sun.
HD 158614 is a spectroscopic binary star system approximately 60 light-years away in the constellation of Ophiuchus.
Beta Hydrae is a double star in the constellation of Hydra. Its overall apparent visual magnitude varies by 0.04 magnitudes with a period of 2.344 days, and is approximately 4.27 at maximum brightness. The brighter star in the double is a giant Bp star which has been classified as an α2 Canum Venaticorum variable.
Xi Hydrae, Latinized from ξ Hydrae, is a solitary star in the equatorial constellation of Hydra. It was also given the Flamsteed designation 19 Crateris. This magnitude 3.54 star is situated 130 light-years from Earth and has a radius about 10 times that of the Sun. It is radiating 58 times as much luminosity as the Sun.
Upsilon¹ Hydrae, also named Zhang, is a yellow-hued star in the constellation of Hydra. It is visible to the naked eye, having an apparent visual magnitude of 4.12. Based upon an annual parallax shift of 12.36 mas as seen from Earth, it is located about 264 light-years from the Sun. The star is moving closer to the Sun with a radial velocity of −14.34 km/s. In 2005 it was announced that it had a substellar companion.
Iota Hydrae, formally named Ukdah, is a star in the constellation of Hydra, about 8° to the north-northwest of Alphard and just to the south of the celestial equator. Visible to the naked eye, it is a suspected variable star with an apparent visual magnitude that ranges between 3.87 and 3.91. Based upon an annual parallax shift of 12.39 mas measured during the Hipparcos mission, it is located around 263 light-years from the Sun.
Omicron Hydrae is the Bayer designation for a solitary star in the equatorial constellation Hydra. At one time it bore the Flamsteed designation 25 Crateris, but this is no longer used by astronomers so as to avoid confusion. With an apparent visual magnitude of 4.70, this star is visible to the naked eye. Based upon an annual parallax shift of 7.27 mas, it is located around 449 light years from the Sun.
Phi3 Hydrae is a binary star in the equatorial constellation of Hydra. It originally received the Flamsteed designation of 2 Crateris before being placed in the Hydra constellation. Based upon an annual parallax shift of 15.49 mas as seen from Earth, it is located around 211 light years from the Sun. It is visible to the naked eye with an apparent visual magnitude of 4.90. It forms a triangle with the fainter φ1 Hydrae and φ2 Hydrae, between μ Hydrae and ν Hydrae.
Chi1 Hydrae is a binary star in the equatorial constellation of Hydra. It originally received the Flamsteed designation of 9 Crateris before being placed in the Hydra constellation. Based upon an annual parallax shift of 22.8 mas as seen from Earth, it is located about 143 light years from the Sun. It is visible to the naked with a combined apparent visual magnitude of 4.94.
Phi1 Hydrae, Latinized from φ1 Hydrae, is a yellow-hued star in the constellation Hydra. Its apparent magnitude is 7.61, making it too faint to be seen with the naked eye. Based upon an annual parallax shift of 12.3 mas as seen from Earth, it is located about 266 light years from the Sun. It forms a triangle with the brighter φ2 Hydrae and φ3 Hydrae, between μ Hydrae and ν Hydrae.
Phi2 Hydrae, Latinized from φ2 Hydrae, is a star in the constellation Hydra. It originally received the Flamsteed designation of 1 Crateris before being placed in the Hydra constellation. Based upon an annual parallax shift of 4.31 mas as seen from Earth, it is located roughly 760 light years from the Sun. The star is faintly visible to the naked with an apparent visual magnitude of 6.09. It forms a triangle with the fainter φ1 Hydrae and the brighter φ3 Hydrae, between μ Hydrae and ν Hydrae.
Eta Crateris is a solitary star in the southern constellation of Crater. It marks the lip of the tilted bowl on the left side in the constellation. Eta Crateris lies in the sky NE of Zeta Crateris and NNW of 31 Crateris, the three stars forming an almost perfect right triangle with Eta at the right angle and 31 and Zeta the ends of the hypotenuse. Eta Crateris also lies to the right (west) of the bright star Gamma Corvi.
κ Hydrae, Latinised as Kappa Hydrae, is a solitary star in the equatorial constellation of Hydra. Its apparent visual magnitude is 5.06, which is bright enough to be faintly visible to the naked eye. The distance to this star is around 135 pc (440 ly), based upon an annual parallax shift of 7.48 mas. It may be a variable star, meaning it undergoes repeated fluctuations in brightness by at least 0.1 magnitude.
