Exoplanets · Space Codex
HD 189733 b
One of the few exoplanets with a measured colour: deep blue, from hazes of silicate particles.
A cobalt-blue world that smells of rotten eggs
Artist's concept. No telescope has seen HD 189733 b as more than a point of light, and most exoplanets not even that. What we know comes from how a planet dims or tugs its star. Any picture of its surface, colour or sky, anywhere, is an illustration, not an observation.
At a glance
Key points
JWST found hydrogen sulfide in its air.
- One of the few exoplanets with a measured colour
- First hydrogen sulfide on an exoplanet
- Silicate haze in a 1,200 K atmosphere
The first map of an exoplanet
In 2007 Spitzer watched the system for half an orbit at 8 microns, seeing the infrared glow rise as the dayside turned towards us. The result was the first rough temperature map of any exoplanet: about 1,210 K at the brightest longitude and 970 K at the dimmest. The modest contrast shows winds carrying heat to the night side, and the hottest region sits east of the point under the star.
Measured blue
Hubble watched the planet's reflected light vanish as it passed behind its star. Blue light dropped; red barely changed. The planet reflects blue strongly, probably from silicate haze particles high in a hot atmosphere.
What JWST added
Hydrogen sulfide, water, carbon dioxide and carbon monoxide, with heavy elements a few times more abundant than in its star.
Observing it
The host star sits about a third of a degree east of the Dumbbell Nebula (M27) in Vulpecula, an easy binocular find in northern summer skies. Each transit dims it by a couple of percent for about two hours, a dip that careful amateurs record with modest telescopes and cameras.
About this view
Artist's concept with one measured property: the deep blue colour (Hubble, 2013). Cloud bands, the eastward-shifted hot spot and the haze texture are illustrative; the night side's 1,000 K glow is too dim to see.
Missions
- 1990–
Hubble Space Telescope
NASA / ESAActiveUltraviolet to near-infrared imaging from low Earth orbit.
- 2021–
Infrared observatory at Sun–Earth L2, about 1.5 million km from Earth.
First-hand · our 3D model
How we render it
HD 189733 b is a hot Jupiter, and its deep blue is the one colour in this set that has been measured (by Hubble in 2013); the cloud bands and haze are illustrative. Zonal bands shear around an equatorial jet, and the hottest point sits 30° east of noon, following Spitzer's phase curve, with a dim thermal glow on the night side. Its 5,052 K star spans about 14° of sky.
No telescope has imaged the surface of any planet shown here, so what you see is an artist's concept: the surface is generated by a shader from noise, not drawn from a map, and its colours and features are illustrative. What is tied to measurement is the starlight and the geometry. The host star's colour is a blackbody at its catalogued temperature, and the planet is tidally locked, with a fixed day side facing the star and a permanent night side.
The host star hangs in the sky at its true apparent size seen from the planet (its radius divided by the orbit), with limb darkening that is stronger in blue and animated granulation. The planet is lit only from that star's direction and in its colour, adapted 40% towards white the way an eye adapts to a single light source. A surface glows only where it is hot enough to glow in visible light, judged from Planck's law at 550 nm. Where the concept has an atmosphere, a ray-marched haze shell adds the limb glow (10 samples at full quality, 6 at reduced, none at minimal).
Related entries
Sources
- NASA Exoplanet Archive: HD 189733 overview (opens in a new tab)
- ESA: Hubble spots azure blue planet (heic1312) (opens in a new tab)
- Fu et al. 2024, Nature (arXiv) (opens in a new tab)
- Knutson et al. 2007, Nature 447:183 (arXiv) (opens in a new tab)
Last reviewed against these sources. Built from public NASA, ESA and JPL data; not affiliated with or endorsed by any agency.