The Discovery of the Galilean Satellites . ... Probably the most significent contribution that Galileo Galilei made to science was the discovery of the four satellites around Jupiter that are now named in his honor. Galileo first observed the moons of Jupiter on January 7, 1610 through a homemade telescope. He originally thought he saw three stars near Jupiter, strung out in a line through the planet. ... Galileo's Observations of Jupiter's Moons . ... Jupiter . ...

Supernova 2009js in NGC 918 . This page is devoted to information on Supernova 2009js in NGC 918 . Basic information on this SN, including the last reported brightness, on this Supernova can be found on the main page . Information on the original web pages for many of these images can be found on the updates and links web pages. Discovered independently by Lick Observatory Supernova Search (USA) and Koichi Itagaki (Japan). ... 2009/10/11.44 . 17.2 . ... Joseph Brimacombe . ...

... Tonight's Sky . ... Observing . ... Sky this Month . ... Astronomy for Kids . ... Can you explain Mercury's retrograde motion? Do other planets appear to do this also? ... When astronomers talk about retrograde motion, generally they refer to the apparent motion outer planets make as Earth passes them while orbiting the Sun. ... Get instant access to subscriber content on Astronomy.com! ... Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter. ...

... Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2014 October 15 . Mysterious Changing feature on Titan . Image Credit: Cassini Radar Mapper , Cornell , JPL , ESA , NASA . Explanation: What is that changing object in a cold hydrocarbon sea of Titan? ... Subsequent observations in 2014 found the object remained -- but had changed! ... About APOD | ... A service of: ASD at NASA / GSFC . ...

... In 1610, Galileo turned his telescope to the heavens and discovered that the planet Jupiter had four bright moons. ... Jupiter's Rings . ... Unlike Saturn's bright rings which are composed of chunks of rock and ice, Jupiter's rings appear to consist of fine particles of dust. ... Exploring Saturn's Rings . ... Saturn's spectacular system of bright rings has been the subject of study and wonder since Galileo first turned his telescope on the ringed planet in 1610. ... M57: The Ring Nebula . ...

home publications > mercury . ... Astronomy Beat . ... Nearly four centuries ago, Galileo's simple observations of Earth's planetary sibling, Venus, buoyed the proponents of a Copernican universe. ... The Italian astronomer had settled into a new house in Florence and had begun to observe Venus, which in November 1610 would have appeared as an evening star, bright in the western sky after dusk. ... From these two observations, Galileo inferred that Venus must orbit closer to the Sun than does Earth. ...

A team of U.S. and German astrophysicists have made the first ever detection of X-rays coming from a comet. ... Following the initial detection, the team reported repeated X-ray emissions from the comet over the next 24 hours. ... One preliminary theory is that X-ray emission from the Sun was absorbed by a cloud of gaseous water molecules surrounding the nucleus of the comet, and then were re-emitted by the molecules in a process physicists call "fluorescence." ... Comets . ...

... Any water on Mars is locked up in the ice caps. ... The most recent successful mission to Mars is the Mars Science Laboratory better known as the Curiosity rover. ... CuriosityтАЩs primary role is to search for conditions that may have once been able to harbour any sort of bacterial life concealed beneath the Martian surface. ... Using what we know about life on Earth, where there is water, there is life, signs of water may help us understand what Mars was like billions of years ago. €а . ...

ASTRONOMY . ASTRONOMY is a science, which studies solids and occurrences in the sky. ... They built the picture of the world according to their knowledge. With the course of time the world picture was being changed because there appeared new facts and information and new theories on the celestial occurrences and what is more impotant there appeared an opportunity to check up the correctness of ideas through the observation and