22-Jun-2012 - Pair of planets orbiting star (Descubren dos Planetas "casi pegados")

Artículo en Español e Inglés
(Spanish & English article)
 English article
In the solar system, the planets' compositions vary with orbital distance, with rocky planets in close orbits and lower-density gas giants in wider orbits. The detection of close-in giant planets around other stars was the first clue oth planets are likely too hot to support life as we know it, with Kepler-36b probably sporting lava flows on its surface. They orbit roughly three times closer to their host star, known as Kepler-36a, than the hellishly hot planet Mercury does to our sun. And Kepler-36a is likely a bit hotter than our star, researchers said.
Every 97 days, Kepler-36b and c experience a conjunction that brings them within just 1.2 million miles (1.9 million km) of each other — roughly five times the Earth-moon distance. This would be quite a sight for an observer on the surface of either planet.

"Planet c would appear roughly 2.5 times the size of the full moon when viewed from the surface of planet b. Conversely, planet b would appear about the size of the full moon on planet c," Carter said.

 Here, we report another violation of the orbit-composition pattern: two planets orbiting the same star with orbital distances differing by only 10% and densities differing by a factor of 8. One planet is likely a rocky “super-Earth,” whereas the other is more akin to Neptune. These planets are 30 times more closely spaced and have a larger density contrast than any adjacent pair of planets in the solar system.

The researchers publish their results Thursday (June 21) in the journal Science.

It is science fiction made fact
Astronomers have discovered two alien planets around the same star whose orbits come so close together that each rises in the night sky of its sister world like an exotic full moon.

The newfound planets are 1,200 light-years from Earth and an unprecedented find, researchers said. They differ greatly in size and composition but come within just 1.2 million miles (1.9 million kilometers) of each other, closer than any other pair of planets known, according to a new study.

One of the newly discovered alien planets, called Kepler-36b, appears to be a rocky "super-Earth" 4.5 times as massive as our planet. The other, Kepler-36c, is a gaseous, Neptune-size world about eight times as massive as Earth. The two planets meet up every 97 days in a conjunction that would make each dramatically visible in the other's sky.

At their closest approach, the two planets are separated by five times the distance between the Earth and the moon.

"This is unprecedented," co-lead author Eric Agol, of the University of Washington, told SPACE.com via email. "They are as different in density as Earth and Saturn yet they are 30 times closer than any pair of planets in our solar system."

Strange neighbors
The two known planets in the Kepler-36 system — which is located in the constellation Cygnus (The Swan) — were detected by NASA's Kepler Space Telescope.

Kepler is staring continuously at more than 150,000 stars, watching for telltale brightness dips caused when planets cross in front of the stars from the telescope's perspective. Since its March 2009 launch, Kepler has flagged more than 2,300 potential alien planets; while only a small fraction have been confirmed to date, mission scientists think more than 80 percent of them will end up being the real deal.

Kepler-36c, which is about 3.7 times wider than Earth, likely has a rocky core surrounded by a substantial atmosphere filled with lots of hydrogen and helium, researchers said.

Kepler-36b, on the other hand, is a super-Earth just 1.5 times wider than our planet. Iron likely constitutes about 30 percent of its mass, water around 15 percent and atmospheric hydrogen and helium less than 1 percent, researchers said.

Though they're very different in size and makeup, the two planets travel on surprisingly similar paths around their host star. Kepler-36c orbits once every 16 days, at an average distance of 12 million miles (19 million km). Kepler-36b orbits each 14 days and sits about 11 million miles (18 million km) from the star.
sciencemag.org, nasa.gov
Artículo en Español

Dos mundos que orbitan extremadamente juntos la misma estrella a 1.200 años luz de la Tierra presentan una impresionante estampa alienígena

Allí, mirar al cielo debe de impresionar de verdad. En vez de una luna como la nuestra, un planeta gaseoso gigante que parece abarcar tres veces más en el cielo se asoma amenazadoramente sobre un paisaje de lava fundida (Foto sup.). Pero estos dos planetas no chocan. Forman parte del sistema Kepler-36, recientemente descubierto por científicos de las Universidades de Washington y Harvard, y orbitan la misma estrella muy cerca el uno del otro.

Ambos mundos orbitan una estrella subgigante muy parecida al Sol, aunque miles de millones de años más antigua.

Una vista espectacular
El mundo interior, Kepler-36b, es rocoso, tiene 1,5 veces el tamaño de la Tierra y un peso de 4,5 veces mayor. Compuesto en un 30% de hierro y en un 15% de agua, orbita su estrella cada 14 días a una distancia media menor de 18 millones de kilómetros. El mundo exterior, Kepler-36c, es un planeta gaseoso 3,7 veces el tamaño de la Tierra y ocho veces más pesado. Este «Neptuno caliente» tiene una órbita de 16 días a una distancia de 19 millones de kilómetros.

Los dos planetas experimentan una conjunción cada 97 días como promedio. En ese momento, están separados por una distancia menor a cinco veces la que hay entre la Tierra y Luna, menos de 2 millones de kilómetros, pero nunca colisionarán. Debido a que Kepler-36c es mucho más grande que la Luna, supone una vista espectacular en el cielo de su vecino. Casualmente, el más pequeño Kepler-36b parece del tamaño de la Luna visto desde el mundo gaseoso. Estos acercamientos despiertan enormes mareas gravitacionales que aprietan y estiran ambos planetas.
Fuente: abc.es

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