Tag Archives: albedo

WASP-104b is Darker than Charcoal

Hot Jupiter WASP-104b was observed in Campaign 14 of the Kepler K2 mission, leading to superb-quality photometry covering 45 orbital cycles of the planet.

Keele graduate student Teo Močnik has analysed the data and concluded that WASP-104b is one of the darkest exoplanets known, reflecting less than 3% of the light from its star.

The conclusion comes from interpreting the “phase curve” produced when the photometry is folded on the planet’s orbital period. Variations in the light are expected to come from the transit and occultation (when the planet passes in front of and behind the star, respectively), from the gravitational distortion of the host star caused by the close-in planet, and from the reflection of starlight.

The phase curve of WASP-104b, as observed by K2, fitted with a red-line model.

The low albedo of the planet is a surprise, but might indicate the absence of clouds (which can be highly reflective) or the presence of ions such as sodium and potassium that absorb light.

The story of WASP-104b was reported by New Scientist, and that then led to articles in Science Alert, Metro, the Daily Mail, Newsweek, the International Business Times, Tech Times and other locations.


WASP-12b a “Blistering Pitch-Black Planet”.

NASA has put out a press release about Hubble Space Telescope observations of WASP-12b. Taylor Bell et al find that WASP-12b “traps at least 94 percent of the visible starlight falling into its atmosphere”, making it “as black as fresh asphalt”.

WASP-12b “as black as asphalt” (Credit: NASA, ESA, and G. Bacon, STScI)

The article explains that WASP-12b, in a very close, 1.2-day orbit, is so irradiated by its host star that “clouds probably cannot form to reflect light back into space. Instead, incoming light penetrates deep into the planet’s atmosphere where it is absorbed by hydrogen atoms and converted to heat energy”. NASA’s press release has led to coverage on several dozen websites.

WASP-12b is one of the more important of the WASP discoveries, with over 30 refereed papers so far focused on understanding it. Most notably, the fierce stellar irradiation means that material is boiling off the planet and forming a cloud surrounding it.