Figure 1: Artist’s impression of a hot Jupiter in a close-in orbit around its host star.
Figure 2: Transit light curve of WTS-2b. Birkby et al. (2014).
WTS-2b raises tides on its host star. The tides exert a strong torque that transfers energy from the planet’s orbit to the star’s spin. This causes the planet’s orbit to shrink and the star to spin up. WTS-2b is estimated to have another ~40 million years before its in-spiralling orbit brings it close enough to its host star to be tidally destroyed. Because WTS-2b transits in front of its host star every 1.02 days, the planet’s shrinking orbit can be directly measured. The in-spiralling is estimated to create a ~17 seconds decrease in the duration between consecutive transits over a period of 15 years.
Most hot Jupiters have orbital periods around 3 to 4 days. There appears to be a lack of hot Jupiters with orbital periods less than 2 days. This could mean that either it is very difficult to get hot Jupiters into very close-in orbits, or that they are quickly destroyed by tidal forces once they are in such orbits. Being so close to its host star, the amount of insolation WTS-2b gets is ~1,000 times more intense than what Earth gets from the Sun. As a result, the day side of WTS-2b is heated to an estimated ~2,000 K.
Birkby et al. (2014), “WTS-2 b: a hot Jupiter orbiting near its tidal destruction radius around a K-dwarf”, arXiv:1402.5416 [astro-ph.EP]