The planet WASP-71b is 1.5 times the radius of Jupiter, the largest planet in our Solar System. It is thus about 15 times the radius of our Earth, making it one of the larger planets we know of.
WASP-71b is just over twice the mass of Jupiter, which means that overall it is less dense, with a density of 2/3rds that of Jupiter.
The star WASP-71 has a radius 2.3 times the radius of the Sun, so it is much bigger. It is also a hotter star with a spectral type of F8. WASP-71 has a brightness of a visual magnitude 10.6.
WASP-71b orbits at a distance of 6.93 million km, taking 2.90 days to go round its orbit.
WASP-71 lies in the constellation of Cetus. Its coordinates are right ascension 01:57:03.0 and declination +00:45:32. The system is at a distance of 350 parsecs from us.
The brightest stars in the plot have magnitude 2 and the faintest have magnitude 6. The visual magnitude of WASP-71 is 10.6, so it is much fainter than these stars, and you would need a telescope to see it.
The star WASP-71 is so big because it is turning into a Red Giant star, which happens when it begins to run out of the hydrogen fuel needed to power the nuclear furnace at its core. Because the star is both big and hot the planet is blasted by fierce radiation, which means that the planet’s gases heat up and expand, making the planet big and hot also.
Since WASP-71 is a large star, the transiting planet blocks less of its light, which means that the transits are shallower than normal for a hot-Jupiter. Only 0.4% of the light is blocked each time WASP-71b transits its star.
The discovery of WASP-71 was announced in 2012 in a paper led by Alexis Smith, then a postdoc working on the WASP project at Keele University, and now working at DLR in Germany.
For more information visit http://exoplanet.eu/catalog/wasp-71_b/.