WASP-6

The planet WASP-6b is 1.22 times the radius of Jupiter, the largest planet in our Solar System. It is thus vastly bigger than Earth.

WASP-6b is about half the mass of Jupiter, which means that, because it is so big, WASP-6b is much less dense than Jupiter. Bloated planets like WASP-6b are thought to contain a lot more heat than Jupiter, and being mostly made of hydrogen gas, they are bigger because hotter gas expands.

The star WASP-6 is 0.87 times the radius of the Sun so it is slightly smaller. Its spectral type is G8 which makes it a yellow dwarf and it has a brightness of visual magnitude 12.4.

WASP-6b orbits at a distance of 6.30 million km from its star, taking only 3.36 days to go round its orbit. That means it takes much less time to orbit than any of our Solar System planets.

From Earth, WASP-6 lies in the constellation of Aquarius. In has the coordinates right ascension 23:12:38.0 and declination -22:40:26. The system is a distance of 307 parsecs away from us.

The brightest stars in the plot have magnitude 1 and the faintest have magnitude 6, so, with a visual magnitude of 12.4, WASP-6 is much fainter.

WASP-6b was the third planet discovered by WASP-South, the Southern WASP camera array situated in South Africa. It was announced in 2009 in a paper led by Michaël Gillon of the University of Liège in Belgium. Prof. Gillon built the TRAPPIST-South telescope which has observed transits of many WASP-South planets.

WASP-6b was observed in 2012 with NASA’s Hubble Space Telescope. It was part of major study of 10 planets that, in the words of NASA’s press release: “solves the missing water mystery”. It had been puzzling that the atmospheres of some planets showed features due to water vapour, but others did not. The study showed that these planets have hazy atmospheres, which blocks the signs of water.

The star that WASP-6b orbits, WASP-6, has “star spots”, just as our sun (left) has “sun spots“. These dark patches are magnetic storms on the surface of the star. We know that WASP-6 has star spots because of what we see when the planet transits across the star:

The four “light curves” at right show the dip in the light from the star when the planet transits across the star. The middle two (blue and green) show a little bump. These tell us that the planet had passed over a star spot. Since the starspot is darker than the rest of the star’s surface, when the planet passes over the spot it blocks out less light than usual, so we see an upwards bump in the light curves. (Paper)

For more information visit http://exoplanet.eu/catalog/wasp-6_b/.

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