{"id":719,"date":"2014-08-25T21:01:53","date_gmt":"2014-08-25T19:01:53","guid":{"rendered":"http:\/\/freebook.fernglas-astronomie.de\/?page_id=719"},"modified":"2014-08-25T21:01:53","modified_gmt":"2014-08-25T19:01:53","slug":"eridanus","status":"publish","type":"page","link":"http:\/\/freebook.fernglas-astronomie.de\/?page_id=719","title":{"rendered":"Eridanus"},"content":{"rendered":"

The river Eridanus is a large and faint constellation, which extends from Orion almost to the southern celestial pole. With the exception of the 0.5m<\/sup> bright Achernar (\u03b1 Eridani, „end of the river“), it contains hardly any noticeable stars and seems very inconspicuous from North America and Central Europe.<\/p>\n

The 3.7m<\/sup> bright \u03b5 Eridani<\/em><\/strong> is 10.5 light-years away, so it belongs to the immediate solar neighborhood. Only two more stars that are visible to the naked eye are closer to us than \u03b5 Eridani \u2013 \u03b1 Centauri and Sirius. The majority of nearby stars are only visible in binoculars or a telescope. \u03b5 Eridani is a young and pretty sun-like star. Mass and diameter are about 85 percent of our Sun, the luminosity is only about one third of the solar luminosity. So far, one planet with 1.5 Jupiter masses was detected around the only 500 million to one billion years old star, and it seems to have a cloud of dust and rock similar to the solar Kuiper Belt, inside which is a space that is large enough for a complete planetary system.<\/p>\n

\u03bf\u00b2 Eridani<\/em><\/strong> is also known as Keid<\/em><\/strong> and only 16.5 light-years away. The 4.4m<\/sup> bright star has an only 9.6m<\/sup> dim companion in a distance of 83 arcsec, which can be seen only in larger binoculars because of the difference in brightness. The companion star is the easiest observable white dwarf star. Its mass is about half the solar mass, while the diameter of 17,000 miles (27,300 km) is about twice as large as that of the Earth. It needs 8,000 years to orbit the primary star once, and is about 400 AU away from the brighter star (1 AU is the distance between Sun and Earth \u2013 about 93.2 million miles or 150 million kilometers). The dwarf star is also surrounded by a 11.2m<\/sup> bright, and only 0.2 solar masses heavy red dwarf star, which remains, however, invisible if you don\u2018t have a large telescope.<\/p>\n

The Witch Head Nebula NGC 1909<\/em><\/strong> is a dim and very large nebula. In 10\u2009\u00d7\u200950 binoculars it may be barely visible under optimal conditions as a 10 \u00d7 50 arcmin large glimmer of light \u2013 Its total size is at least 1 \u00d7 3\u00b0. It is probably a reflection nebula illuminated by the bright star Rigel, but it could also be a supernova remnant. It is located 2.5\u00b0 away from Rigel (\u03b2 Orionis) and Cursa (\u03b2 Eridani). You can give it a try if you have really dark skies.<\/p>\n","protected":false},"excerpt":{"rendered":"

The river Eridanus is a large and faint constellation, which extends from Orion almost to the southern celestial pole. With the exception of the 0.5m bright Achernar (\u03b1 Eridani, „end of the river“), it contains hardly any noticeable stars and seems very inconspicuous from North America and Central Europe. The 3.7m bright \u03b5 Eridani is … Eridanus<\/span> weiterlesen →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":714,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-719","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"http:\/\/freebook.fernglas-astronomie.de\/index.php?rest_route=\/wp\/v2\/pages\/719","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/freebook.fernglas-astronomie.de\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"http:\/\/freebook.fernglas-astronomie.de\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"http:\/\/freebook.fernglas-astronomie.de\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/freebook.fernglas-astronomie.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=719"}],"version-history":[{"count":1,"href":"http:\/\/freebook.fernglas-astronomie.de\/index.php?rest_route=\/wp\/v2\/pages\/719\/revisions"}],"predecessor-version":[{"id":720,"href":"http:\/\/freebook.fernglas-astronomie.de\/index.php?rest_route=\/wp\/v2\/pages\/719\/revisions\/720"}],"up":[{"embeddable":true,"href":"http:\/\/freebook.fernglas-astronomie.de\/index.php?rest_route=\/wp\/v2\/pages\/714"}],"wp:attachment":[{"href":"http:\/\/freebook.fernglas-astronomie.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=719"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}