The smallest exoplanet ever photographed

Among the few extrasolar planets directly observed, researchers immortalized with the help of the Japanese Subaru telescope a planet which has less mass, perhaps as little as three times that the mass of Jupiter. GJ 504 b, this is its name, orbits at 60 light years away around a star similar to the Sun.

GJ 504b


So as to allow synthesis admirable as that which describes the last trophy brought home by Subaru, the Japanese 8.2-meter telescope on top of Mauna Kea, Hawaii: a Jupiter-like planet around a Sun-like star. That translated into a language lacking of practical like it would be a Jupiter-like planet in orbit around a star similar to the Sun. Nothing extraordinary, you say? Yeah, if it were not that the Jupiter-like world (code name: GJ 504 b) is the smallest planet ever photographed; the photography was, in fact, taken by Subaru.

The last census says that there are about 900 confirmed planets orbiting stars other than the Sun. Of these planets, however, very few are those actually observed through a telescope: in most cases it is confirmed in an indirect way, either because they induce changes in the radial velocity of the parent star, or because passing in front for some time reducing the apparent brightness. And the few planets immortalized are all very large and – at least for cosmic standards – very young: no more than 50 million years.

It’s too bad, because direct observations allow us to obtain crucial information, such as those relating to the brightness, temperature, atmosphere and orbit of these worlds. On the other hand, they are small and dull as compared to the parent star and being able to catch a sight is really a business: it’s like trying to see a firefly while circling around a distant lighthouse, scientists say.

GJ 504b - 2


In short, it is the stuff of Instagram: to try, you need the best possible equipment and a team of experienced astronomers. Like those of the project SEEDS: formed by researchers from the TiTech (Tokyo Institute of Technology), the University of Tokyo and of NAOJ (the National Astronomical Observatory of Japan), SEEDS has available as a telescope Subaru – not new to these exploits – equipped at all points, from the adaptive optics coronagraph . These two are indispensable tools, on one hand, to remove the blinding light of the parent star and on the other hand, the perturbations introduced by the atmosphere. But we also need a lot of patience to make sure that what was found it’s a real planet and not a star in the background.

The result, however, has awarded the tenacity: the isolated dot near GJ 504 (a star about 60 light years from Earth, visible to the naked eye in the constellation Virgo), with an estimated mass of between 3 and 8 times that of Jupiter and more or less 160 million years old, is the oldest and smallest exoplanet that has ever been directly detected to date. A crucial step towards direct observation, in the near future, a world of Earth -like. And that means that an image will be shared on the bulletin board.

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