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 . Misconceptions . ... Bitesize Astronomy . ... Keep Bad Astronomy close to your heart, and help make me filthy rich. ... Comets are not "dirty snowballs" . ... Miscellaneous nonsense . ... Imagine McCanney's scenario: an asteroid the size of the Moon is moving through the solar system. ... The particle is moving pretty fast, and that motion has energy (called kinetic energy). ... Obviously, that's so much energy that it would easily vaporize the comet. ... 2008 Phil Plait. ...

... 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 . ...

... Planets . ... Stars . Exoplanets . ... Most exoplanets so far discovered fall into the category of тАШhot JupitersтАЩ, these are giant planets orbiting very close to their parent star. ... Note that we have discovered so many hot Jupiters because they are the easiest type of planet to find, they are not necessarily particularly common in the galaxy. ... Subsequently several similar hot and€а fuzzy worlds have been discovered the same way, proving this that this planet is not a one-off oddball. ...

... Star Atlas . ... Gravitational wave search provides insights into galaxy evolution and mergers . ... galaxies . ... The double star 54 Leonis, spiral galaxy NGC 3198, and emission nebula NGC 3199 . ... Astronomy for Kids . ... Dave's Universe . ... Everything around us is spinning: particles, planets, stars, galaxies. ... Planets rotate, as do stars and galaxies. ... Get instant access to subscriber content on Astronomy.com! ... If you are already registered on Astronomy.com, please log in below. ...

... 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. ...

... 11.12.2001 . Venus, second planet from the Sun, appears above imaged for the first time ever in x-rays (left) by the orbiting Chandra Observatory. ... Stars, like bees, swarm around the center of bright globular cluster M15. ... But only since 1999 have observers seen elusive optical flashes on the lunar surface - likely explosions resulting from impacting meteoroids. ... Comet Linear (WM1) Brightens . ... Dueling Auroras . ... Will it be curtains for one of these auroras? ... First page ] Prev. ...

The Search for Planets Around Other Stars As we live out our lives securely attached to the Earth, breathing its air, and using its water, it becomes all too easy to take planets for granted. ... Yet the surprising fact is, we do not know for certain whether there are planets around other stars. ... A few years ago there was a flurry of excitement as some astronomers found wobbles in the motions of several nearby stars, suggesting the presence of planets. ... a stillborn star, if you will ? ...

Circling around magnetic field lines. ... The ring current . Because positive ions and negative electrons drift in opposite directions (see drawing), that motion will create an electric current that circulates clockwise around the Earth when viewed from north. ... How then can the radiation belt and ring current arise? ... Electric fields are able to push trapped particles earthward, and unlike the purely magnetic motion described earlier, an electric field can also energize them. ...

... Files in red?history) . ... Trapped Motion . ... 10a. Particle Drift . ... Fast Particles . ... The fact charged particles circle around field lines was well known to J.J. Thomson when he experimented with electron and ion beams in a magnetic field. ... The notion of adiabatic invariance is tied with the early years of quantum theory. ... By about1910, physicists realized that these patterns indicated changes in the laws of physics as one approached atomic dimensions. ...

... 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 . ...

... Satellites of the planets are assigned a provisional designation (indicating year of discovery) by the Central Bureau for Astronomical Telegrams ( CBAT ) upon satisfactory demonstration of the existence of a new object. ... In the past, Comets were first given a provisional designation, consisting of the year and a lowercase letter indicating the order of discovery in the year (e.g., 1994a was the first comet discovered or recovered in 1994, 1994b the second, etc.) ... Names .. ...

The radiation belts around the planets are the interrnal regions of planets' magnetospheres where the own magnetic field of a planet keeps the charged particles (protons and electrons) having the great kinetic energy. ... They usually distinguish the Earth's internal and external radiation belts. the internal radiation belt of the Earth has the maximum particles density (mainly protones) over the equator in the height of 22 thousand km. ... Jupiter and Saturn have the powerful radiation belts. ...

. [ Go back to Comet WWW site ] . Andrew A. Martis . martis @ sai.msu.ru .

My research efforts have focused on three areas which are: . More than 200 extrasolar planets have been discovered around relatively nearby stars, primarily through the Doppler line shifts owing to the reflex motions of their host stars, and more recently through transits of some planets across the face of the host stars. ... Gravitational microlensing provides a novel technique to look for planets around lens stars, and this is the only technique currently capable of detecting Earth-mass planets. ...

Pulkovo Database of Observations of Minor Planets and Comets . Select an object and the time interval . Minor planets with long-term observations - - - - - - select an object - - - - - - 1 Ceres 2 Pallas 3 Juno 4 Vesta 6 Hebe 7 Iris 11 Parthenope 18 Melpomene 25 Phocaea 39 Laetitia 40 Harmonia 389 Industria 532 Herculina 704 Interamnia 762 Pulkova . ... Select database . ...

... Given the observing time and frequency, task plplt plots the expected visibility function for a planet. You will most likely want to check this visibility function before observing and discovering that the planet is resolved out! NOTE that mfboot and plplt do not include the effect of the ATCA's primary beam - the planet is implicitly (and silently) assumed to be small compared with the primary beam. ... Information on using the ATCA to observe a planet is available on-line . ...

... Many massive planets contrary to Jupiter have large eccentricities of orbits. ... Another problem is to study the conditions and boundaries of stable, regular motions of small mass planet in systems having `Jupiter' with large orbital eccentricity as well as properties of regular, stable, and irregular, chaotic motions. ... The regular eccentricity evolution described above demonstrates that stable quasi--circular orbits of small planet are unusual. ...

... The study of extra solar planets will be one of the most important areas of research in astronomy in this century. ... The first planets outside the solar system were found in 1992 around the millisecond pulsar PSR B1257+12 by Alex Wolszczan at the Arecibo Observatory . ... Three space missions based on this principle (MOST, COROT and Kepler ) have already been launched or approved, and have the last one at least has the potential to find Earth-sized planets. ... SIM ( NASA ) is one of such missions...