Hydra

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Hydra

a genus of the coelenterate class Hydrozoa. Most species are found in freshwater, and are unusual members of the Hydrozoa in not having an ALTERNATION OF GENERATIONS.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
References in periodicals archive ?
For a change of pace, jump from Nu to Mu ([mu]) Hydrae, then look a half binocular field south for the 7.7-magnitude planetary nebula NGC 3242, also known as the Ghost of Jupiter (see page 56).
The team's observations indicate that particles with a diameter of 1.0 to 1.4 cm lie within the disk that surrounds TW Hydrae, Wilner and his colleagues report in the June 20 Astrophhisical JournaI Letters.
Additional evidence hints that at least one planet has already formed around TW Hydrae, Wilner says.
The easternmost star in this triangle, Mu Hydrae, lies 1 3/4[degrees] north of NGC 3242, the bright planetary nebula called "the Ghost of Jupiter."
East of Mu Hydrae is brighter Nu Hydrae--and they form the base of an equilateral triangle whose northerly apex is U Hydrae, one of the reddest of all stars in binoculars and small telescopes.
For instance, if a faint dot of light in the TW Hydrae association really is a planet, it should move in 1 year a distance roughly equal to one-thirty-thousandth the width of the full moon on the sky, says Schneider.
In contrast, the nearby TW Hydrae association includes just a few dozen newborn stars but covers a section of sky 15 to 20 degrees wide.
The other two Messier objects, M83 and M68, lie at the eastern end of Hydra and form a roughly equilateral triangle with 3.0-magnitude Gamma (a) Hydrae, the constellation's second-brightest star.
These stars are C Hydrae and its attendants, which no longer belong to the Unicorn (Monoceros), according to modern constellation boundaries.
About 8[degree sign] to the south-southeast lies another carbon star, V Hydrae. It has been ranging from magnitude 6 to 10 in recent years with a period of about 550 days.
R Hydrae's average peak magnitude is usually listed as 4.5, but in fact it has not been seen that bright since 1943.