The pink planet

What is exoplanet GJ 504 b and why is is confusing astronomers?


NASA 800px-Astronomers_Image_Lowest-mass_Exoplanet_Around_a_Sun-like_Star

GJ 504 b is a recently announced Jovian planet that rests around 57 light years away from Earth around the yellow dwarf star 59 Virginis. It was picked up by the 8.2-metre Hawaiian Subaru Telescope that operates in the infrared wavebands.

At around four times the mass of Jupiter yet similar in size, this distant world – which astronomers believe is coloured in magenta – is the smallest as well as one of the most ancient worlds that we’ve directly imaged at around 160 million years old. You might think that the strangest thing about this planet is that it’s the only pink world that we know of – but there’s more to it than that – causing astronomers to place it up there as one of those weird worlds that they’re having their work cut out in understanding.

Resting around nine times the distance that Jupiter orbits from our Sun, GJ 504 b certainly poses a challenge for our ideas of how giant planets form. It has long since been thought that gaseous worlds begin their lives in gas-rich debris discs surrounding a young star. However, experts are the first to admit that this only really holds true for planets as far out as blue planet Neptune leaving us with no option but to give our theories some tweaking.

“There are two mechanisms that are postulated as to how planets form,” Oxford University’s professor of astrophysics, Niranjan Thatte told, “One is to grow them from planetesimals, the so-called ‘core accretion’ process, although this mechanism cannot really explain forming large planets at distances larger than 30 times the Earth-Sun distance.”

“On the other hand, GJ 504 b could have formed by fragmentation of the protoplanetary disc (the gas cloud from which it formed) but then it is subject to forces that drag it inwards due to interaction with the same disc, so it would not normally be expected to survive that either. Hence the difficulty in explaining how such a planet could exist in a 160 million-year-old system.”

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