Saturday, 23 May 2015

It is called Gliese 581d

Gliese      Andrea Catalán

It is called Gliese 581d and orbits the star of the same name (without the last letter), a red dwarf star located 20 light years from Earth, along with five other worlds, some also very interesting. The extrasolar planet was discovered in 2009 by researchers at Queen Mary College London and Hertfordshire, who presented it as the first super-Earth found in habitable zone, ie, a world of a size somewhat larger than ours which is the right distance from their star to support liquid water on its surface, an indispensable condition for the existence of life as we know it.

The candidate planet was discovered using a spectrometer that measures the "wobble" small changes in the wavelength of the light emitted by a star caused by a planet orbiting around it. However, a report published last year in Science magazine rejected the existence of this planet, considering what astronomers saw was nothing more than "stellar activity disguised as a planet." In his view, the world was actually supposed noise in the data caused by star spots.

The "fathers" of the "d" are not achantado, insist that their planet exists and ensure that the findings of his colleagues have been caused by inadequate analysis of the data. The statistical technique used in the investigation of 2014 to account for stellar activity is, as explained, "just enough" to identify smaller planets as Gliese 581d.

In his view, that approach has worked in the past in identifying the larger planets because its effect on the star was too important to deny the errors in the results. However, it makes it almost impossible to find smaller planets signals within the noise caused by the stellar variability itself.

"It has always been there"
Using a more accurate model on existing data, researchers are convinced that the signal GJ 581d is real, despite the stellar variability. "The existence (or not) of GJ 581d is significant because it was the first similar to Earth discovered in the" Goldilocks "planet (the habitable zone, not too hot, not too cold, as in the fairy tale) about another star (where water can exist in liquid form) and is a reference case for the Doppler technique, "explains Guillem Anglada-Escudé, lead author of the article.

"There are always discussions among scientists about the way we interpret the data, but I'm sure 581d has been in orbit around Gliese 581 all the time," added the researcher. "In any case, the strength of his statement was too strong. If his treatment of the data is correct, then some projects search for planets in Earth-based observatories have to be revised significantly as they are intended to detect even smaller planets. You have to be more careful with these claims, "he warns.


The star Gliese 581 is a source of findings for planet hunters, but also a source of controversy. In 2010, astronomers at the University of California Santa Cruz and the Carnegie Institution of Washington announced the discovery of the first planet "really living" outside our solar system, the planet 'g', another of the six known worlds of the system. As has happened with his brother 'd', the 'g' was also questioned just a few weeks after being announced officialy, but also in the same way, the discovery team turned to bring new evidence that seemed to confirm their existence. Certainly not fail to give Gliese surprises


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