There鈥檚 never a cloudy day on WASP-96b. This hot gas giant may have the least cloudy skies on any exoplanet astronomers have ever seen, and consequently, that makes it a great place to plumb the depths and study in what might be happening below the planet鈥檚 clear skies.
鈥淏y 鈥榗lear鈥� we mean cloud-free, which means the actual atmosphere is moderately see-through,鈥� says at Exeter University in the UK.
at NASA鈥檚 Jet Propulsion Laboratory in Pasadena, says, 鈥淭his is one of the, if not the, clearest atmospheres detected to date.鈥�
Advertisement
While the distance to the planet鈥攁nd the uniqueness of the observation鈥攈olds the team back from knowing precisely how far this translucence goes, Kataria says the spectral observations let us see fairly far down into the atmosphere.
A blue hue
Though the planet is the size of Jupiter, it鈥檚 only half the mass. On examining the atmosphere, the astronomers saw an abundance of sodium, which, thanks to its absorption of orange-yellow light would give the planet a blue hue to聽an observer. The team can鈥檛 rule out clouds deeper down in the atmosphere, beyond the thinner upper layers
The observations were made on the Very Large Telescope in Chile, and mark some of the best-ever measurements of an exoplanet鈥檚 atmosphere. The researchers witnessed two transits of the planet as it crossed in front of its star, allowing them to measure the light as it passed through the atmosphere.
They detected relatively high amounts of sodium. That they were able to measure the amount of sodium made the observation unique among exoplanet atmospheric observations, which tend towards detecting tracers of the chemicals, but not knowing their abundance.
鈥淚t鈥檚 really great to see ground-based work of this fidelity,鈥� says at the Space Science Telescope Institute in Baltimore, Maryland, who was not involved in the study.
Training wheels
The team also demonstrated that future, larger telescopes like the James Webb Space Telescope should be able to easily tell the abundance of other chemicals 鈥� including water vapour 鈥� in the atmosphere of exoplanets. A clear planet like WASP-96b would allow astronomers to see more than just the surface layer, and confirm some theories we have about how gas giants form.
Lewis says the team has demonstrated one of the best places to study exoplanet atmospheres of any planet discovered thus far. 鈥淵ou can go in with an expectation that you鈥檒l get a strong signal with Webb instead of blindly pointing at [another random planet] and hoping for the best,鈥� Lewis says.
That could enable us to find out about the interiors of gas giants in other planetary systems and find out how they came together. It could also tell us about our own gas giants, including what鈥檚 going on deep below their upper cloud layers.
It could also lead the way toward techniques for determining not just if smaller exoplanets have oxygen or water vapour, but if they have the right abundances of them for life. This is all just training wheels for the day we detect oxygen, Lewis says.
Nature
Read more: NASA has launched a new space telescope to hunt for exoplanet
