WASP-33b

In 2010, the SuperWASP project announced the discovery of an extrasolar planet orbiting the star HD 15082. The discovery was made by detecting the transit of the planet as it passes in front of its star, an event that occurs every 1.22 days. ==Orbit==

A study in 2012, utilizing the Rossiter–McLaughlin effect, determined the planetary orbit is strongly misaligned with the equatorial plane of the star, misalignment equal to −107.7°, making the orbit of WASP-33b retrograde. The periastron node is precessing with a period of 709 years. ==Physical characteristics==

Limits from radial velocity measurements imply it has less than 4.1 times the mass of Jupiter. The transit was later recovered in Hipparcos data. ==Atmosphere==

In June 2015, NASA reported the exoplanet has a stratosphere, and the atmosphere contains titanium monoxide, which creates the stratosphere. Titanium monoxide is one of only a few compounds that is a strong absorber of visible and ultraviolet radiation, which heats the atmosphere, and is able to exist in a gas state in a hot atmosphere. This was later confirmed using high-resolution spectroscopy technique with the data taken by High Dispersion Spectrograph mounted on the 8.2 m Subaru Telescope. The detection titanium monoxide was not be able to be reproduced with the higher quality data obtained by 2020 although with different setting of observations. Only upper limit of titanium monoxide volume mixing rate equal to 1 ppb can be obtained. Later research reconfirmed the existence of titanium monoxide in the atmosphere of WASP-33b, although in concentrations not detectable by HARPS-N. The neutral iron and silicon were also detected. In 2020, with the detection of secondary eclipses (when the planet is blocked by its star), the mass of the planet along with temperature profile across its surface was measured. WASP-33b has strong winds in its atmosphere, similar to Venus, shifting the hottest spot 28.7±7.1 degrees to the west. The averaged wind speed is 8.5 km/s in the thermosphere. The illuminated side brightness temperature is , while the nightside brightness temperature is . The water in dayside atmosphere of WASP-33b is mostly dissociated to hydroxyl radicals due to high temperature, as planetary emission spectra indicated which was the first detected hydroxyl radicals on a planet outside the Solar System. ==Non-Keplerian features of motion for WASP-33b==

In view of the high rotational speed of its parent star, the orbital motion of WASP-33b may be affected in a measurable way by the huge oblateness of the star and effects of general relativity. First, the distorted shape of the star makes its gravitational field deviate from the usual Newtonian inverse-square law. The same is true for the Sun, and part of the precession of the orbit of Mercury is due to this effect. However, it is estimated to be 9 \times 10^9 greater for WASP-33b. ==See also==