Astronotes Armagh Planetarium's Stellar Blog! ... Planets . Comets and Asteroids . ... Stars . Exoplanets . ... Space Flight . ... The exoplanet HD 209458b has a mass more than 200 times Earthт??s and has a diameter greater than Jupiterт??s. It orbits its star at about an eighth of the distance Mercury orbits the sun, so the exoplanet takes only 3.5 days to complete an orbit. This proximity to a star means that the planet is hot, perhaps 1000ТАC, hence it is classed as a т??hot Jupiterт?? ...

... Tonight's Sky . ... The Magazine . ... Star Atlas . ... An artificial comet holds secrets to Earths life . ... Astronomy for Kids . ... Observing springtime deep-sky objects with a large telescope . ... The planet has extreme temperature swings and perhaps active lava flows. ... A digital supplement to Astronomy magazine. ... Join TravelQuest International with Astronomy and Discover magazines on one of three great tour options surrounding this celestial spectacle . ... Astronomy Magazine . ...

3) Planets and Brown Dwarfs . ... By its nature, this method is most sensitive to massive planets orbiting close to their stars. ... That means that some of the more massive extrasolar planets could actually be brown dwarfs (although the statistics of the finds suggest that most of them are not). ... Another possible difference between brown dwarfs and massive planets is how they are born. ... They would base the fundamental definition on the mode of formation: a planet is built from planetesimals. ...

... Bad Astronomy . ... Bitesize Astronomy . ... If you thought our tour of the solar system ended with Neptune and Pluto, you are setting your sights way too low. The planets of the solar system mark time relatively close to the Sun compared to interstellar space. Pluto orbits the Sun at an average distance 40 times that of the Earth, yet the nearest star (the Alpha Centauri system) to the solar system is a mind-numbing 260,000 times the distance of the Earth to the Sun. ... 2008 Phil Plait. ...

... Comet Ikeya-Zhang, designated C/2002 C1 (Ikeya-Zhang), is named after Kaoru Ikeya of Shizuoka prefecture, Japan, and Daqing Zhang of Henan province, China, who independently discovered it on the night of 1 February 2002. A preliminary orbit reported the following day indicated that it would come moderately close to both the Earth and the Sun and that it might become visible to the naked eye during late March and April 2002. ... Bailey, M.E., Clube, S.V.M. and Napier, W.M. The Origin of Comets . ...

... Science User Portal . ... For the first time, astronomers have been able to directly follow the motion of an exoplanet as it moves from one side of its host star to the other. ... Only 12 million years old, or less than three-thousandths of the age of the Sun, Beta Pictoris is 75% more massive than our parent star. ... This research was presented in a paper to appear this week in Science Express (тАЬA Giant Planet Imaged in the disk of the Young Star Beta Pictoris,тАЭ by A.-M. Lagrange et al.) ...