Monday, July 15, 2013

The first exoplanet that around a solar-type star

That blue dot in the upper right is Gliese 504b (GJ 504b), a giant planet that is 59 light years from Earth orbiting a solar-type star. But what is this special? Have we not already seen several extrasolar planets directly? Yes, but doing a little cheating. And is that exoplanets we have seen directly, as the system HR 8799, for example-are actually training worlds still shine with their own light, especially in infrared. 

Gliese 504B is nevertheless a planet much more 'cold', with a temperature 'surface' of about 240 ° C, and is also the first exoplanet that we can see with our own eyes situated around a Sun-like star (GJ 504 is spectral type G0). Until now we had only seen directly planets orbiting stars much larger and younger. It is also the first exoplanet to be discovered around a star rich in "metals"-that is, basics heavier than helium.

Not that Gliese 504b is old, and that his age is estimated at 100-500 million years, but it certainly is by far the oldest exoplanet we've been able to discover without using indirect methods such as traffic or the radial velocity. Like most worlds that can be seen directly, Gliese 504b is located a great distance from its star: about 6.525 billion kilometers (43 AU), which is enough when compared to the 4.5 billion kilometers (30 AU) the orbit of Neptune. And, like most giant planets located at this distance jeopardizes the planet formation mechanism known as core accretion, thus favoring the other rival model based on gravitational instability. But it is also perfectly possible that GJ 504b has migrated out of the system due to gravitational interactions with other hypothetical inner planets.

Unfortunately, having been discovered by direct vision is difficult to determine the mass of this planet, but it is believed could be between 3 and 8.5 times the mass of Jupiter. All further indicates that GJ 504b has a bluish color, which could be a sign of the presence of an atmosphere with few clouds and make this world a future candidate for spectroscopic observations. GJ 504b has been discovered by the project team SEEDS (Strategic Explorations of Exoplanets and Disks with Subaru) Japanese Subaru telescope. Between March 2011 and May 2012, the SEEDS team observed the object in infrared to make sure it really is in orbit of GJ 504 and is not an independent body. Now we can say we've seen, but seen 'of verdad'-a planet around a solar-type star. 

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