Thursday, August 14, 2008

EXOPLANETS


Left, explanation. (U/California). At the telescope, we measure the change in the wavelength (color) of light coming from a star over the course of days, months, and years. This changing wavelength is the Doppler shift of the light, resulting from the star orbiting a common center of mass with a companion planet. For example, Jupiter's gravitational pull causes the Sun to wobble around in a circle with a velocity of 12 meters per second.



Thanks to analysis of oscillations of light (radial velocity method/doppler shift due to stellar wobble), coming from suns different to our, induced by appearances and disappearances of celestial bodies orbiting around them, has been possible to document the existence -since 1991 to the date- of around 300 exoplanets. A fact that has allowed to David Bennett (U/Notre Dame), , to calculate that for each 2 present suns in our galaxy, exists at least 1 exoplanet, with what it would exist around 50 billion planetary systems alone in our Milky Way. An amazing number that favors the possibility of existence of life outside of our planetary system. Nevertheless the data regarding this last declaration, are not good. Most of discovered exoplanets to the date are gassy, inhospitable and orbit very near their suns, being for that denominated "hot Jupiter". Nevertheless, another group of scientists adduces that the littleness and scarce glow of many exoplanets, prevent to discover them with the current technology.


Exoplanet search has facilitated meanwhile, to discover extrasolar systems with up to 7 exoplanets (55 Cancri System). Some exoplanets has been silent witness and resisted the hot expansions of their stars about to collapse for exhaustion of its internal helium. Other stayed frozen at certain distance of their suns. Other, superhot goes losing its gassy atmosphere, as long as they orbit near its sun. Some scientists have seen the genesis of some exoplanets to the interior of accretion disks. The European satellite Corot, and the NASA, have begun recently an aggressive program of exoplanet search with the last aim of identifying planets similar to ours, able to harbor life.
EXOPLANETAS

Merced a análisis de oscilaciones de la luz (método de velocidad radial/doppler shift due to stellar wobble), procedentes de soles distintos al nuestro, inducidas por apariciones y desapariciones de cuerpos celestes orbitantes alrededor de ellos, ha sido posible documentar la existencia -desde 1991 a la fecha- de alrededor de unos 300 exoplanetas. Un hecho que le ha permitido a David Bennett (U/Notre Dame), calcular que por cada 2 soles presentes en nuestra galaxia, existe al menos 1 exoplaneta, con lo que existirían alrededor de 50 billones de sistemas planetarios solo en la en la Via Láctea. Una barbaridad, que favorece la posibilidad de existencia de vida fuera de nuestro sistema planetario. No obstante los datos respecto a este ultimo aserto, son desalentadores. La mayoría de exoplanetas descubiertos a la fecha son gaseosos, inhóspitos y orbitan muy cerca de sus soles, siendo por ello denominados “Jupiter calientes”. No obstante, otro grupo de científicos aduce que la pequeñez y brillo escaso de muchos exoplanetas, impide descubrirlos con la tecnología actual.


La búsqueda de exoplanetas ha posibilitado mientras tanto, descubrir sistemas extrasolares con hasta 7 exoplanetas (55 Cancri System). Algunos exoplanetas han sido mudos testigos y resistido expansiones y calentamientos de sus estrellas a punto de colapsar por agotamiento de su helio interno. Otros se mantienen helados a cierta distancia de sus soles. Otros, supercalientes van perdiendo su atmósfera gaseosa, en tanto orbitan cerca de su sol. Algunos científicos han visibilizado incluso, la génesis misma de algunos exoplanetas al interior de discos de acreción. El satelite europeo Corot, y la NASA, han iniciado recientemente un agresivo programa de identificación de exoplanetas, con el fin último de identificar planetas semejantes al nuestro, capaces de albergar vida.

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