Hydra (constellation)
- Alpha - hydrides
- Cup
- Lion
- Unicorn
- Aft deck of the ship
- Marine Compass
- Centaur
- (Wolf)
- Scale
- Virgo
The water snake or Hydra is a constellation south of the celestial equator.
Description
The water snake is the most extensive constellation in the night sky. It extends below the constellations (Cancer ), Lion (Leo) and Virgin (Virgo ) and can be observed by our latitudes in spring deep on the southern horizon.
The water snake is not very striking, as most of its stars are faint. Only the main star Alphard is 1.98 m strikingly bright
History
The " female " or large water snake is one of the constellations of ancient Greek astronomy, which have already been described by Ptolemy.
In the 16th century, the "male", Southern or Little Water Snake ( Hydrus Latin ) was introduced. This constellation is however so far south that it is not observable from Europe.
Mythology
For mythological origin, there are two versions:
After the First, the water snake represents the many-headed Hydra monster that struck the marshes surrounding the city Lerna. The hero Heracles was the task has been transferred to slay the beast. But Heracles had to realize that for each head, which he struck off the Hydra with the sword, two new nachwuchsen. At the same time he was attacked by a giant cancer. Heracles succeeded to crush the cancer, but he was able to defeat the Hydra only with the help of his nephew Iolaus. This had brought in firewood and burned every time Heracles had separated a head of the monster, the wound, so no more heads could grow back. The Hydra, cancer and Heracles (Hercules ) were immortalized as constellations in the sky.
Another version brings the water snake with the neighboring constellations Raven ( Corvus ) and cup ( Crater ) in conjunction. Accordingly, the god Apollo sent out a raven, which should bring fresh spring water for Zeus. The Raven grabbed a golden cup, and flew to the source. On the way he saw a fig tree whose fruit but were still immature. Although Apollo had ordered him to lose no time, the raven waited several days until the fruit was ripe, and cutting himself so fully. In order to avoid punishment, he grabbed a water snake, flew with it to Apollo and claimed that the queue have him blocking the way, so he could not return until now. Apollo saw through the liar and threw him to the warning, including the snake and the cup to the sky.
Celestial objects
Stars
α Hydrae is an orange shining star of spectral type K3 in 177 light years away. The name Alphard is derived from the Arabic al farad from, which translates as " the single person " means. Another name is Cor Hydrae, "Heart of the water-snake".
Double stars
ε Hydrae is a binary star system 100 light -years away. To resolve it into individual stars you need a telescope from 8 cm opening.
τ1 Hydrae appears in the prism binoculars as a double star. In fact, it is an " optical " double star whose components are not connected by gravitation, but only seen from Earth lie in a direction
27 Hydrae is a multiple star system in which three stars orbit around a common center of gravity. Even in a small telescope from 6 cm opening all three components are visible.
R Hydrae is a Mira -type star pulsationsveränderlicher in 500 light years away. At the maximum, it reaches a brightness of 3.5 m, the minimum brightness drops to 10.9 m from. The brightness varies with a period of around 387 days. Records have shown that the period in the 18th century was around 500 days much longer.
U Hydrae is a 2,000 light years distant star whose brightness varies with a period of about 450 days. At the maximum, it reaches a brightness of 4.7 m and can be seen with the naked eye. At a minimum, its brightness drops to 6.2 m, so that you can its observation requires a pair of binoculars. While the minimum he is striking reddish.
V Hydrae is a deep red star, similar to Mira. The brightness varies between 6.5 m and 12.5 m.
Messier and NGC objects
M 48 is an open cluster in 2,500 light years away, which already offers a pair of binoculars a rewarding sight.
M 68 is a 30,000 light-years distant globular clusters. It can be resolved only with a larger telescope in single stars.
M83 is a spiral galaxy of type Sc in about 15 million light -years away. It is already to be seen in binoculars as a misty patch. In the larger telescope to a bright core and approaches of spiral arms show. From Germany, it is not easy to observe, since it is low on the horizon and hinder the denser layers of the atmosphere the view.
NGC 3242 is a planetary nebula in 3,000 light- years away. At high magnification it is visible as a greenish discs in the telescope. Since its apparent diameter in the sky corresponds approximately to that of the planet Jupiter, he is also called Jupiter's spirit.
NGC 3314 are two interacting galaxies 140 million light years away.