... Jupiter's moon Io is turning out to be our Solar System's geologic powerhouse. ... In a report released yesterday and soon to be published in Nature, astronomers have imaged an interesting distant patch of sky with the orbiting Hubble Space Telescope. ... Also known as the Seven Sisters and M45, the Pleiades is one of the brightest and most easily visible open clusters on the sky. Sirius: The Brightest Star in the Night . ... Sirius is the brightest star in the night sky. ...