Windsup to 8 700 km/hfrom the day side to the night side[2]
Host starK2 V, 5 052 K (4 780 °C)an orange dwarf with a companion star[1]
About the image. Drawn deep blue, the colour Hubble measured in 2013. The cloud patterns are imagined, and the glass rain is an explanation of the data, not something that has been seen.
24×as wide as our Sun looks from Earth
340×the light Earth gets
Thought to be tidally locked: the star stays putNo ground: the view from the cloud tops
The sky from HD 189733 b
HD 189733 A would look 24× as wide as the Sun does from Earth, and the planet gets 340× as much light as Earth gets.
Its colour comes from its surface temperature of 5 052 K (4 780 °C); the Sun's is about 5 772 K (5 500 °C).
HD 189733 b is thought to be tidally locked: one side always faces the star.
There are no sunrises. Where you stand decides where the star hangs, overhead on the day side, low at the edge, gone on the night side.
Apparent size = star radius ÷ orbit; light = size² × (temperature ÷ 5 772 K)⁴. Both from the values on this page. The landscape is imagined.
HD 189733 b was found in 2005 by a French team at the Haute-Provence Observatory, a gas giant a little larger and heavier than Jupiter that circles its orange star in just over two days. Each time it crosses the star it blocks about 3 percent of the light. It is the closest transiting hot Jupiter to Earth, only 64 light-years away, and that has made it one of the most closely studied planets outside the Solar System.
A blue planet
In 2013 a team led by Tom Evans used the Hubble Space Telescope to measure the light reflected by the planet just before and during the moment it passed behind its star. The planet reflected far more blue light than green or red. Earlier polarisation measurements had pointed the same way, and HD 189733 b became the first planet whose colour was determined by two different techniques. Seen up close it would be a deep cobalt blue.
It is not blue for the same reason as Earth. There is no ocean: the planet is a scorching gas giant at over 1 200 K (927 °C). One explanation is high clouds of silicate particles, tiny grains of glass, which scatter blue light. In that heat they may condense and fall as rain of molten glass, while winds of up to 8 700 kilometres per hour carry heat from the day side to the night side.
A chemistry lab
Few planets have had their atmosphere read in such detail. Water was found in 2007, methane in 2008, and carbon monoxide on its day side in 2013. It was the first planet outside the Solar System confirmed to have carbon dioxide. In 2024 hydrogen sulfide was detected, the gas that gives rotten eggs their smell.
In 2007 Heather Knutson’s team used the Spitzer telescope to make the first temperature map of an exoplanet. They found the hottest spot pushed about 30 degrees east of the point directly under the star, swept along by those winds. In 2010 Hubble also saw hydrogen escaping from the planet: it is losing somewhere between 1 000 and 100 000 tonnes of gas every second. The planet is thought to be tidally locked, with one side always facing its star.
Its orbit, to scale
HD 189733 b goes around once every 2.2 days, at 0.03126 AU from its star. The whole view is tiny on Solar System scale: Mercury orbits the Sun about 12 times farther out than the outermost orbit shown here.
Earth days passing: 0
To scale · radius, Jupiter = 1Earth: 0.089 · Jupiter: 1.00 · HD 189733 b: 1.13
How hot is it?
Earth (average)288 K · 15 °C
Water boils373 K · 100 °C
Venus surface737 K · 464 °C
Iron melts1 811 K · 1 540 °C
Sun's surface5 772 K · 5 500 °C
HD 189733 b1 209 K · 936 °C
HD 189733 b: equilibrium temperature. Logarithmic scale from 100 K to 10 000 K. Reference values: NASA, IAU.
How long to get there?
HD 189733 b is about 64 light-years away.
Light299 792 km/s64 years
Breakthrough Starshotplanned light sail, 20% of light speed320 years
Parker Solar Probefastest spacecraft so far, 192 km/s99 931 years
Voyager 1leaving the Solar System, 17 km/s1.1 million years
At Voyager 1's speed the trip would take about 14 108 human lifetimes of 80 years. Bars are on a logarithmic scale. Speeds: NASA, Breakthrough Initiatives.
Your weight on HD 189733 b
On HD 189733 b
Gravity there is about 2.24× Earth's, at the cloud tops; there is no surface. Calculated from the measured mass and radius.
Gallery
A deep blue gas giant with pale streaked bands, lit by a small orange star at its left edge, an impression of HD 189733 b. AI-generated painting.The curved blue horizon of a planet streaked with cloud, with a small orange star just above it, an impression of HD 189733 b. AI-generated painting.HD 189733 b, 3D artist's impression, rendered from the interactive model.HD 189733 b, 3D artist's impression, from another angle, rendered from the interactive model.HD 189733 b, 3D artist's impression, close-up, rendered from the interactive model.
Timeline
2005Discovered by a French team at the Haute-Provence Observatory.
2007Spitzer makes the first temperature map of an exoplanet; water is detected.
2010Hubble sees hydrogen escaping from the planet.
2013Hubble measures its deep blue colour.
2024Hydrogen sulfide is detected in its atmosphere.
Questions people ask
Why is HD 189733 b blue?
Probably because of high clouds of silicate particles that scatter blue light, not because of water. It is a gas giant at over 1 200 K (927 °C).
Does it really rain glass on HD 189733 b?
It may. Silicate particles could condense in the atmosphere and fall as molten glass, but the rain has not been observed directly.
How fast are the winds on HD 189733 b?
Up to about 8 700 kilometres per hour, carrying heat from the day side to the night side.