Australia is currently in the midst of a drought, and we welcome any amount of rain with open arms. But if you were to take a quick holiday to some of the exoplanets that we have discovered you would be more hesitant to ask for a little precipitation.
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Take the wonderfully named HD 189733b for instant, which was discovered in October, 2005.
At a first glance, you might think it was a great place to go for a visit: a large, beautiful blue planet quite like Earth.
But upon closer inspection you would be in for a shock. For one thing, the planet orbits 10 times closer to its host star than Mercury, resulting in toasty temperatures of around 1000 degrees Celsius. Furthermore, the winds of this planet are absolutely terrifying, blowing around 8700km/h - or two kilometres per second!
But the deadliest thing about this planet is the reason for its blue colour. The NASA Hubble Space Telescope measured the visible light of the planet in 2013 and found that the planet scattered more blue than red light, not due to oceans or water, but rather due to clouds made of silicate particles (like sand). These particles can then melt in the extreme temperatures and get blown around by the wind, essentially creating a swirling vortex of glass rain falling horizontally! The weather here sure is a cut above the rest.
The next time you consider taking a vacation to an exoplanet in our local neighbourhood, make sure you check the weather forecast. You could be in for a wild time.
Even more recently, in early March, astronomers at the European Southern Observatory (of which Australia is an associate member) observed a planet of even larger extremes: WASP-76b.
WASP-76b is also an exoplanet, meaning it exists outside of our solar system and orbits around a star.
This exotic exoplanet is located some 640 light-years away in the constellation of Pisces.
This planet orbits about the same as HD189733b, but the star is much hotter causing daytime temperatures over 2400 degrees Celsius. This is enough to vaporise metals such as iron into its atmosphere!
WASP-76b is also tidally locked, meaning the same side always faces the sun as it orbits. This results in the night side being cooler, a still scorching 1500 degrees Celsius.
What makes this interesting though is that strong winds can carry the vaporised metals to the evening border that separates night from day on the planet.
This cools down the metals, causing it to condense like rain - which is exactly what was detected by scientists. Essentially, WASP-76b is prone to a light evening shower of iron!
So the next time you consider taking a vacation to an exoplanet in our local neighbourhood, make sure you check the weather forecast. You could be in for a wild time.
- Jonah Hansen is a PhD student specialising in space interferometry at Mount Stromlo Observatory, at the Australian National University.
