Latest Circumstellar discs Stories
Astronomers using NASA's Spitzer Space Telescope have discovered a remarkably small brown dwarf surrounded by a dusty disk. The brown dwarf contains only about 8 times the mass of Jupiter.
Brown dwarfs, like more massive normal stars, are formed when interstellar gas and dust clouds collapse. When this happens, a central, dense area builds up, embedded in a rotating disc made of gas and dust. These circumstellar discs produce infrared radiation according to their temperature.
Newborn stars are difficult to photograph. They tend to hide in the nebulous stellar nurseries where they formed, enshrouded by thick layers of dust.
According to the most popular theory of planet formation, planets are akin to redwood trees, growing in size very gradually. Rocky planets like Earth develop over millions of years, followed by gas giants like Jupiter, which build upon rocky cores. But new evidence suggests that some gas giants may sprout in less than one million years, more like planetary wildflowers than trees.
Using NASA's Spitzer Space Telescope, a team of astronomers led by the University of Rochester has detected gaps ringing the dusty disks around two very young stars, which suggests that gas-giant planets have formed there. A year ago, these same researchers found evidence of the first "baby planet" around a young star, challenging most astrophysicists's models of giant-planet formation.
Astronomers report tremendous quantities of warm dusty debris surrounding a star with luminosity and mass similar to the sun's, but located 300 light-years from Earth. The extraordinary nature of the dust indicates a violent history of cosmic collisions between asteroids and comets, or perhaps even between planets. The discovery is published July 21 in Nature.
A relatively young star located about 300 light-years away is greatly improving our understanding of the formation of Earth-like planets.
Every rule has an exception. One rule in astronomy, supported by considerable evidence, states that dust disks around newborn stars disappear in a few million years. Most likely, they vanish because the material has collected into full-sized planets. Astronomers have discovered the first exception to this rule - a 25-million-year-old dust disk that shows no evidence of planet formation.
Interstellar travelers might want to detour around the star system TW Hydrae to avoid a messy planetary construction site. Astronomers have discovered that the gaseous protoplanetary disk surrounding TW Hydrae holds vast swaths of pebbles extending outward for at least 1 billion miles.
Dusty disk around Fomalhaut makes ideal laboratory for studying planet formation.
Cosmogony -- Cosmogony is the study of the origins of celestial objects. It is most commonly used to refer to the study of the origin of the solar system. Currently, the most widely accepted theory is that the solar system was formed roughly 5 billion years ago with the collapse of a nebula of gas and dust, likely caused by shock waves generated by a nearby supernova. The solar system would have formed as a member of a star cluster, now long-since dispersed throughout the Milky Way over...
Asteroid Belt -- The Asteroid belt is a region of the solar system falling roughly between the planets Mars and Jupiter where the greatest concentration of asteroid orbits can be found. It is believed that, during the first million years of the solar system history, planets formed by accretion of planetesimals. Ripetute collisions led to the familiar rocky planets and to the gas giant's cores. However, in this zone of the system the strong gravity of Jupiter inhibited the final stages...
Vega -- Vega (Alpha Lyrae) is the lead star in the constellation Lyra, reaching near directly overhead the mid-northern latitudes, during the summer. It's a "nearby star" at only 25 light years distant and together with Arcturus and Sirius, one of the brightest stars in the Sun's neighbourhood. Vega is a vertex of the Summer Triangle. Its spectral class is A0V (Sirius, an A1V, is slightly less powerful) and it's firmly in the main sequence, fusing hydrogen to helium in its core....
Epsilon Eridani -- Epsilon Eridani is a main-sequence star in the constellation of Eridanus (the river). It is often used in science fiction because it is extremely sunlike, and in the fictional Star Trek universe it is the home sun of the planet Vulcan which is home to Mr. Spock. It is the third closest star visible without a telescope. It has 85% of the Sun's mass, almost that much of its diameter, and 28% of its luminosity. It is 10.5 light years from Earth. Its spectrum is...
- Small missiles, especially grape, canister, fragments of iron, and the like, when fired, as upon an enemy at close quarters.
- To fire mitraille at.