HD 189733 b

HD 189733 b is a hot Jupiter orbiting the star HD 189733 about every 2.2 days. Its atmosphere scatters blue light and has measured winds reaching several kilometers per second.

Connect

Hot Jupiter: A gas giant orbiting close to its star, with an orbital period typically shorter than ten days. HD 189733 b belongs to this close-in class, whose intense stellar heating shapes its atmosphere.
HD 189733: A nearby K-type star that hosts the transiting hot Jupiter HD 189733 b. The planet’s orbit, transits, and observable atmosphere are measured against this bright host star.
Exoplanet: A planet orbiting a star other than the Sun. HD 189733 b is studied as a planet beyond the Solar System.
WASP-12b: An extremely hot gas giant on a close orbit around the star WASP-12. It provides a contrasting hot Jupiter whose intense heating and atmospheric loss have been studied.
Atmospheric escape: The loss of gas from a planetary atmosphere into space. Ultraviolet heating drives hydrogen escape from HD 189733 b’s upper atmosphere.
HD 189733 b blue color: The blue optical appearance of HD 189733 b, inferred from reflected-light observations. This observed color inspired the planet’s popular description as a deep-blue world.
Transit method: A technique for detecting planets by measuring periodic dips in a star’s brightness as a planet crosses its disk. Its transits established the planet’s presence and make atmospheric observations possible.
HD 209458 b: A transiting hot Jupiter orbiting the star HD 209458. Its early atmospheric detections offer a landmark comparison with observations of HD 189733 b.
Rayleigh scattering: The preferential scattering of light at wavelengths much shorter than the scattering particles. Scattering in the atmosphere contributes to the planet’s blue appearance.
HD 189733 b atmospheric winds: Rapid atmospheric flows on HD 189733 b inferred from spectroscopic measurements. Doppler shifts in atmospheric sodium indicated winds reaching several kilometers per second.