W Hydrae

W Hydrae is a variable star ( Mira star) in the constellation of Hydra, according to Hipparcos Catalogue about 115 parsecs ( about 375 light years) from the Sun. His visual apparent magnitude varies between 5.6 and 10 in the near infrared (J- band ) is its apparent magnitude -1.7, so that it appears in this area than the siebthellste star ( for example, brighter than Sirius ).

Water and dust

The star also shows the water that indicate the existence of an extended disk of dust and gaseous water intensive emissions. The source of such emissions spans an area with a diameter between 0.182 " and 36 '. This corresponds to the above-mentioned removal of a dust disk with an inner radius of about 10.5 astronomical units (about the distance of Saturn from the Sun ) and an outer radius of about 2 light-years (ie approximately 125,000 astronomical units, that is, slightly more than the extent of the Oort cloud in the solar system ).