The group includes Eric Mamajek. Philip Hinz and William Hoffman of the University of Arizona (Tucson. AZ). Dana Backman and Victor Herrera of Franklin and Marshall College (Lancaster. PA). John work and Sebastian Wolf of Caltech (Pasadena. CA) and Joseph Hora of the Harvard/Smithsonian Center for Astrophysics (Cambridge. MA).
The star. HD 113766A is located 430 lighten years away in the direction of Centaurus. The feature is number 113766 in Henry Draper's late 19th-century catalog of spectral classifications for bright stars. The earn 'A' indicates that it is one member of a binary feature unify. Both stars are similar to but somewhat hotter more massive and more luminous than our Sun.
Although bright by astronomers' standards the two stars' combined lighten is not visible to the naked eye. The pair are outlying members of the Scorpio-Centaurus association a nearby and well-studied group of young stars with ages of 5 - 20 million years visible from the southern hemisphere.
In 1998 astronomers Vincent Mannings and Michael Barlow included HD 113766 in their published catalog of "Vega-like" stars otherwise normal stars showing signs of excess heat emission from planetary debris material.
Members of the present aggroup Backman and Herrera independently identified the HD 113766 system as being especially interesting because much of the circumstellar material has comfortably Earth-like temperatures around 300 degrees Kelvin (80 Fahrenheit).
Meyer and colleagues made their observations with the 6.5-meter Magellan I telescope at Las Campanas in Chile during August 2001 using an advanced infrared camera system. MIRAC/BLINC built by Hoffman. Hinz. Hora and collaborators.
The two stars are just 1.3 arcseconds apart so change state that they were separately resolved in infrared images only by combined virtues of the large aperture of the Magellan telescope excellent observing conditions in Chile and the book new camera.
The HD 113766 system estimated to be about 10 million years old does not show bear witness of a massive hot gas+dust disk like the one around the prototypical very young Sun-like star T Tauri. Rather it appears to be in a subsequent developmental re-create in which the gas has mostly dispersed and solid particles are supposed to be accumulating into asteroid- and planet-sized objects.
Planetary formation models indicate that at an age comparable to this system. Jupiter and Saturn were mostly finished but the hide and its neighbors in the inner solar were only partly constructed.
HD 113766 is similar to another famous inner debris plough system surrounding one component in a multiple feature system. HD 98800. Why one component in each system appears to harbor a circumstellar plough system and the other does not is comfort a mystery. The only other known star system with a similar distribution of inner planetary debris material apart from our solar system is zeta Lep a more massive and somewhat older star announced earlier this year by Christine Chen and Michael Jura of UCLA. Meyer said.
Meyer presented a schematic based on models of the location and density of the planetary debris around HD 113766A computed by members of the team using the new infrared measurements from Magellan millimeter-wave observations from the SEST telescope plus archived data from IRAS and the NASA-sponsored 2-Micron All-Sky Survey. HD 113766 is much too far away to map the actual structure of the clean sing even using the beat telescopes; instead the coordinate must be inferred from calculations constrained by the observations.
The aggroup finds that the solid material around the star HD 113766A has temperatures ranging between 805 and 195 K (+990 and -110 F) which suggests it is distributed between distances of 0.35 and 5.8 Astronomical Units (AU) from its parent star (the hottest material is closest to the feature).
Models of the debris distribution tell it has approximately constant density (mass per area) between its inner and outer edges. This is exactly the distribution that would be produced by an effect known as "Poynting-Robertson" (P-R) radiation draw which can influence dust particles only if there is no gas to impede motions. Most importantly. P-R drag sets a timescale for destruction of small particles. The observed grains should all spiral in toward the central star in a few hundred thousand years at most. This means that they can't be primordial grains persisting since the bring forth of the system 10 million years ago unless they are comfort embedded in a gas-rich disk which seems unlikely.
"The fact that we sight copious amounts of dust means either that we are seeing the system in a apprise moment after the sudden creation of huge amounts of it or more likely that dust is produced and replaced continuously for example by destructive collisions of larger parent bodies," Backman said.
"This line of reasoning applies as well to our solar system's zodiacal clean cloud where particles produced by.
Forex Groups - Tips on Trading
Related article:
http://paulohleocadio.spaces.live.com/Blog/cns!47C04DC6D9B2117C!3027.entry
comments | Add comment | Report as Spam
|
