Imagine a planet that seems enchanting at first glance, with a beautiful blue glow, almost as if you were looking at a second Earth. But this blue-colored exoplanet, HD 189733 b, is anything but a peaceful, oceanic world. In reality, it is a planet that defies everything we know about weather systems.
Welcome to HD 189733 b: another world
HD 189733 b is located in the constellation Fox, about 64 light years away from us. In cosmic terms, that's relatively close. At first glance, this planet looks somewhat like Jupiter, but its blue color quickly confuses you. That color does not come from water, as we might be used to on Earth. In fact, on HD 189733 b the atmosphere has very different properties.
Contrary to what you might think, the blue on HD 189733 b is the result of something you would probably never expect: a “storm” of glassy particles is constantly blowing, scattering sunlight and giving the planet its blue hue. So that calming blue color? That one is actually the result of one of the most deadly weather systems imaginable.
Glass rain at 8,700 kilometers per hour
The most bizarre thing about HD 189733 b is undoubtedly the weather. Imagine if it could rain near us at speeds of thousands of kilometers per hour. It sounds absurd, but on HD 189733 b this happens every day. Here it rains molten glass. Because of the tremendous heat in the atmosphere, which can reach more than 1,000 degrees Celsius, silicon particles are heated and evaporate. When this silicon vapor cools a bit, the particles condense back into glassy droplets that fall back to the planet.
But because the winds on HD 189733 b are racing at speeds of up to 8,700 kilometers per hour, these glass particles are not falling straight down as rain falls in our case. No, this “rain” is blown horizontally, like a dangerous storm of sharp, glass particles that would destroy everything in its path. This combination of wind and glass rain makes HD 189733 b unlivable and extremely unsafe - a literal killing storm.
The intense closeness to his star
HD 189733 b orbits its star incredibly close, much closer than Mercury orbits the sun. Where Earth takes a year to orbit the sun, HD 189733 b does so in just 2.2 days. Because of this proximity, the planet is constantly bombarded by radiation and heat from its star, and this has major implications for its atmosphere and weather patterns. The powerful radiation literally vaporizes the planet's atmosphere; HD 189733 b is constantly losing layers of its atmosphere to space.
This intense sunlight also creates extreme temperature differences between the side facing the star and the side in shadow. These temperature differences are partly the cause of the planet's raging winds - the weather tries to balance the heat differences, but never fully succeeds.
Why is HD 189733 b of interest to scientists?
HD 189733 b is more than just a curiosity; it is a valuable source of knowledge about the extremes of our universe. By studying planets like this one, scientists are learning how planets and atmospheres function in conditions completely different from Earth's. The glass rain and extreme temperatures of HD 189733 b show us how diverse and surprising planets can be, even compared to the giant planets in our own solar system.
Moreover, HD 189733 b offers us insight into how atmospheres can change and disappear under the influence of extreme radiation. This also helps astronomers understand how planets with atmospheres, such as our own Earth, evolve and what it takes to keep that atmosphere stable.
What does the future of HD 189733 b look like?
Although it is a fascinating world for us to study, HD 189733 b probably has a bleak future. Because it is so close to its star, its atmosphere will continue to evaporate. It is a slow process, but eventually the planet may lose its entire atmosphere and become a barren, dead world. This is a natural process that could take billions of years, but it is a fascinating lesson for us about the long-term effects of radiation and intense sunlight on a planet.
What can we learn from HD 189733 b?
HD 189733 b shows that the diversity of planets is endless and that nature goes far beyond our imagination. Where our Earth has calm rain showers, HD 189733 b has storms of glass and ferocious, hyper-powerful winds. By exploring this planet, we are reminded that the universe is full of worlds that challenge the laws of nature and continue to spark our imagination.
In this new blog series on planets you won't believe, we will explore many more of these bizarre worlds. HD 189733 b is just the beginning - a first glimpse of how strange and enriching the cosmos can be. Keep following us to discover even more of these incredible worlds.
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