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 which occurs every 1.22 days. As the planet crosses the star's disc, it causes the rotational broadening signature in the star's spectrum to change, enabling the determination of the sky-projected angle between the star's equator and the orbital plane of the planet to be determined. (This differs from the Rossiter–McLaughlin effect which is observed for radial velocity measurements.) For HD 15082 b, this angle is about 250 degrees, indicating that it is in a retrograde orbit. Limits from radial velocity measurements imply it has less than 4.1 times the mass of Jupiter.[1] The exoplanet orbits so close to its star that its surface temperature is about 3,200 °C (5,790 °F).[4] The transit was later recovered in Hipparcos data.[5]

June 2015 NASA reported the exoplanet has a stratosphere, and the atmosphere contains titanium oxide which creates the stratosphere. Titanium oxide is one of only a few compounds that is a strong absorber of visible and ultraviolet radiation, which heats the atmosphere, and able to exist in a gas state in a hot atmosphere.[6][7] The detection of temperature inversion (stratosphere), water and titanium oxide was disproved with the higher quality data obtained by 2020. Only upper limit of titanium oxide volume mixing rate equal to 1 ppb can be obtained.[8]

Atmosphere of WASP-33b was detected by monitoring light as the planet passed behind its star (top)—higher temperatures result in the low stratosphere due to molecules absorbing radiation from the star (right)—lower temperatures at higher altitudes would result if there were no stratosphere (left)[6]

In 2020, with the detection of secondary eclipses (when the planet is blocked by its star), the mass of planet along with temperature profile across its surface was measured. The WASP-33b have a strong winds in its atmosphere similar to Venus, shifting hottest spot 28.7±7.1 degrees to the west. The illuminated side brightness temperature is 3014±60 K, while nightside brightness temperature is 1605±45 K.[3]

In view of the high rotational speed of its parent star, the orbital motion of HD 15082 b 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 ${\displaystyle 9\times 10^{9}}$ greater for HD 15082b.[9]

Other effects will also be greater for HD 15082b. In particular, precession due to general relativistic frame-dragging should be ${\displaystyle 3\times 10^{5}}$ greater for HD 15082b than for Mercury, where it is so far too small to have been observed. It has been argued that the oblateness of HD 15082 could be measured at a percent accuracy from a 10-year analysis of the time variations of the planet's transits.[9] Effects due to the planet's oblateness are smaller by at least one order of magnitude, and they depend on the unknown angle between the planet's equator and the orbital plane, perhaps making them undetectable. The effects of frame-dragging are slightly too small to be measured by such an experiment.