Comets are small, fragile, irregularly shaped bodies composed of a mixture of non-volatile grains and frozen gases. ... Most become visible, even in telescopes, only when they get near enough to the Sun for the Sun's radiation to start subliming the volatile gases, which in turn blow away small bits of the solid material. ... Nearly 100 known comets have periods (the time it takes them to make one complete trip around the Sun) five to seven Earth years in length. ...

... Bad Astronomy . ... Bitesize Astronomy . ... Last week's Snack talked about how black holes can affect the environment around them in such a way as to be very bright . ... It's a common misconception that black holes always have matter swirling into them. ... As this matter gets closer and closer to the black hole it piles up and a large, fairly flat disk forms. This is called the accretion disk , because matter from this disk accretes (that is, falls in) on the black hole. ... 2008 Phil Plait. ...

... The awsome spectacle of a brilliant comet, with its long ghostly tail streaming behind it, is a rare event. ... Only one other comet, Comet Halley, was seen so far from the Sun, giving scientists an opportunity to watch it as it slowly warmed up and sprouted a tail. ... Comets are the Rip Van Winkles of the solar system -- mini-worlds that have changed little during their 4.5-billion-year nap far from the Sun. ... Observing Comets . ... Once, comets inhabited the entire solar system. ...

The basic problems of the Laboratory are connected with researches of dynamics of minor planets and comets. ... THE ORBIT IMPROVEMENT of minor planets from optical and radar observations, . the utilization of minor planet observations for THE DETERMINATION OF ORIENTATION OF STAR CATALOGUES and DETERMINATION OF MASSES OF MINOR PLANETS BY DYNAMICAL METHOD, . THE ESTIMATION OF COLLISION PROBABILITY of minor planets with other bodies and with each other, . ...

... Many consider him the greatest navigator of Europe's 16th century age of sea going exploration and credit his expedition with the first circumnavigation of planet Earth. ... A comet nucleus, formed from the primordial stuff of the solar system, resembles a very dirty iceberg. ... Pluto: The Frozen Planet . ... Pluto is usually the most distant planet from the Sun but because of its elliptic orbit Pluto crossed inside of Neptune's orbit in 1979 and will cross back out again in 1999. ...

Check out some poking around I've been doing on comet and asteroid dynamics from various databases. Comets are bad for our health! Well, at least over the long term-- look at what just *one* fragmet of Shoemaker-Levy 9 (the comet which impacted Jupiter in July of 1994) would have done had it hit Michigan instead of Jupiter! ... Charles Morris' JPL Comet Page . Mike A'Hearn's Home Page . Casey Lisse's Home Page . Small Bodies Node ...

... 2013 March 15 . CME, Comet and Planet Earth . Image Credit: NRL / SECCHI / STEREO / NASA . ... But this remarkable interplanetary perspective from March 13, finds the comet posing with our fair planet itself - as seen from the STEREO Behind spacecraft. ... At the left an enormous coronal mass ejection (CME) is erupting from a solar active region. Of course, CME, comet, and planet Earth are all at different distances from the spacecraft. The comet is closest.) ... About APOD | ...

... 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 . ...

Astronotes Armagh Planetarium's Stellar Blog! ... Armagh Planetarium . ... Solar System . ... Planets . ... Space Flight . ... Neptune, which is not visible with the naked eye, was discovered by mathematical prediction in 1846 before being observed through a telescope. ... Tidal interactions between Neptune and Triton mean that in 100 million years these two bodies may come too close to one another causing Triton to be torn apart leaving Neptune with a ring system more spectacular than SaturnтАЩs. ...

... Solar System . ... Sun . ... Comets . ... Some get thrown out of the solar system forever, whereas others end up on yet smaller orbits, visiting the inner solar system fairly frequently - such as comet Halley. ... When a comet moves into the inner solar system, this is heated by the Sun, and the ices turn into gas which forms the head or coma of the comet, which may be hundreds of thousands of kilometres across and visible from Earth. The most striking part of many active comets is the tail . ...

... Comet Animation . ... Comet structures are diverse and very dynamic, but they all develop a surrounding cloud of diffuse material, called a coma, that usually grows in size and brightness as the comet approaches the Sun. ... As comets approach the Sun they develop enormous tails of luminous material that extend for millions of kilometers from the head, away from the Sun. ... The evaporated molecules boil off and carry small solid particles with them, forming the comet's coma of gas and dust. ...

... More on 51 Peg: . The discovery of a Jupiter--mass planet in orbit around the solar--type star 51Peg has been reported by Michel Mayor and Didier Queloz (Geneva Observatory) on October 6th at the 9th Cambridge workshop on "cool stars, stellar systems, and the sun" held at Florence (Italy). ... Recall that the measurements of radial velocity only yield v sin i which in turn gives us M sin i. For most values of i, sin i will be greater than 0.5 and this gives a mass estimate of 0.5 Jupiter masses. ...

... SATELLITE: An object that revolves around a planet. ... SIDEREAL DAY: The length of a planet's rotation period relative to the stars. SOLAR SYSTEM: The sun and all the objects that are held in its gravitational field and move around it. ... SUPERIOR CONJUNCTION: The position of a planet when it is on the opposite side of the Sun from Earth (thus making in invisible). ... TRANSIT: The movement of an object between the Earth and the Sun and showing on the surface of the sun as a black dot. ...

The small solids. Asteroids or the small planetes . ... The comets. ... Ceneca the Young.Procuring about the nature.63 y. The comet is a celestial body of a great size, but a rare one... transparent. Sometimes there seen a core and the medium forms a kind of a tail, beard or dishevelled looks. ... The core is an ice body - conglomeration of frosted gas and dust. ... The comet state is variable: ones have the con tails, others the dust tails, and the third have both. ... Meteors and meteorites. ...

... part 1 | ... The Basic Stages in Earth's Pre-geological Development . ... After fragments of the Vortex sleeves separated, whirlwinds of second and third orders ("NC" - new micro-vortex) were generated- future planet cores and their satellites - all of them developing independently, governed by the common laws of development of cosmogenic vortexes. ... Our planet's core today is comprised of considerably deteriorated cosmogenic vortex; consequently, the Earth has a moderated magnetic field. ...

... Future seminars . P a s t seminars . ... Ejection of material from a comet after its collision with a smaller body, probabilities of collisions of migrating small bodies and dust particles with planets, and formation of small body binaries " . ... The probabilities of collisions of different small bodies (asteroids, comets, and trans-Neptunian objects) and dust particles of different sizes produced by these bodies with all planets are considered for dynamical lifetimes of bodies and particles. ...

... Articles | ... Forums . ... 230 deg . 49 deg . ... 130 deg . ... More Info . ... 210 deg . ... 168 deg . ... 249 deg . ... 195 deg . ... 271 deg . ... 110 deg . ... 338 deg . ... July 15 . 247 deg . ... 224 deg . ... 340 deg . ... July Phoenicids (PHE) . ... August 10 . 341 deg . ... 339 deg . ... 307 deg . ... 334 deg . ... 335 deg . ... 286 deg . ... 327 deg . ... 262 deg . ... 102 deg . ... 153 deg . ... 117 deg . ... December 2 . ... 123 deg . ... 100 deg . ... www.astronomy.net . ...

... ESO, the European Southern Observatory . ... Visits to ESO Sites . ... Survey Telescopes . ... Star Clusters . ... Stars@ESO . ... Educational Material . ... ESO 3.6-metre telescope . ... MPG/ESO 2.2-metre telescope . ... TRAnsiting Planets and PlanetesImals Small Telescope . ... Particles in the dust ring are kept inside the ring by gravitational interactions with planets. The faster-moving inner planet transfers energy to dust particles, moving them outward, deeper into the ring. ... Fomalhaut . ...

... A rough estimation is that in the United States there is one planetarium per 100,000 population, ranging in size from the Hayden Planetarium's 20-meter dome seating 430 people, to three-meter inflatable portable domes where children sit on the floor. ... Together dblo associates make a huge impact in the architecture, interior design and development arena in London. ... With the holidays around the corner what better way to spoil your family than with your very own private home cinema. ...

... Dept. for Astrometry & Space Geodynamics . ... Dept. for Physics of Stars&Galaxies . ... Dept. for Physics of Planetary Systems . ... Science . ... All Pages . ... Research of the stars with planets which pass apparent star disk (transiting exoplanets). The transit method based on a detection star brightness decrease during a passing of planet in front of its disk. Observed brightness system decries when planet pass star disk and its volume depend of the relative sizes star and planet. ...