Gliese 581, G: It is Reportedly The First Habitable Planet Mirage?

Less than three weeks ago, U.S. astronomers announced the discovery of planet Gliese 581 g, where the surface may be "conditions of life. Worldwide hype then cut short by a few words in a half-hour lecture.

Steve Vogt and his colleagues announced the discovery a few days before the fifth and sixth planets of Gliese 581, which can be found in the constellation Libra at a distance of about 20 light years.

Professional and general public interested in particular the discovery of an exoplanet Gliese 581 g, which has a weight of about 3.1 to 4.3 Earth. The radius of the distant world should move depending on the chemical composition from 1.3 to 2 earth radii. Gliese 581 g has around its parent star orbit with a period of less than 37 days in the habitable area, which means that the planet’s surface may find the conditions to sustain liquid water.

A team of astronomers used data from the discovery of the HIRES spectrograph, which is installed on one of the two Keck telescopes in Hawaii. In addition, earlier used data from the HARPS spectrograph, which can be found on the large 3.6 m telescope of the European Southern Observatory in Chile. In both cases, the astronomers were available for 120 measurements. If the U.S. was a spectrograph data for the past 11 years, the European Harps of the published data from 2004 to 2007.

On Monday 11 began in October in Turin, Italy, the five-day symposium of the International Astronomical Union on extrasolar planets. Already on Monday morning should be presented in about half an hour lecture HARPS spectrograph results of that for the period from 2008 to today. Logically be expected that a central part of the paper will be about exoplanetÄ› Gliese 581 g. But the way to the surprise of everyone present had happened. “You can not (Gliese 581 g) to confirm our data in the HARPS” said Francesco Pepe from the Geneva Observatory.

Francesco Pepe introduced the particular new data from the HARPS spectrograph, which was acquired in 2008. These 60 new measurements added 120 European astronomers measure for the years 2004 to 2007, they worked with the American team.

Pepe and his colleagues on the basis of the data confirmed the existence of four previously discovered planets of Gliese 581 (b, c, d, e). New acquisitions – Gliese 581, Gliese 581 g f, however, were caught from the data. Pepe has said that the changes in amplitude of the radial velocity is very small and can be a normal noise.

Where’s the Beef?

The discovery was in itself since the beginning, but two-rooted problems. The first is that the planet was discovered using the radial velocity and do not carry any transit.

Indeed, if we discover exoplanets, which transits (moving from its star, causing the periodic dips in its brightness), we get immediately the radius of exoplanets. For each transiting planets can then obtain the weight of the radial velocity of the parent star. Based on these two figures, it can calculate the density of the planet, but perhaps more importantly, the discovery of an exoplanet is confirmed by a second and independent method.

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