JON CULSHAW
Jon’s travels take him to the scorching world as black as bitumen
Auriga, the Charioteer, is a prominent and familiar constellation in our winter night sky. A well-known and welcome icon in the sky during those long dark nights, it brings a reassuring feeling when we look at it. It’s amazing, therefore, to consider that one of the most unnervingly unusual and extreme exoplanets exists within it.
Around the star Wasp 12 – a yellow G0 star of 1.4 solar masses and 1.6 solar radii, very similar to our own Sun – is the hottest of the ‘hot Jupiters’. Gas giant planets of this class orbit tightly around their host stars and – quite naturally – are scorching and searing as a result.
The planet in question, Wasp 12b, is a mightily severe and hostile environment indeed. This month’s trip promises to be exciting and nerve-wracking in equal measure. Described in terms that would suit the voice of Darth Vader, what manner of terrifying place could this “black hot Jupiter feasting upon light” possibly be?
After making the 871-lightyear journey to Wasp 12 it is staggering to see just how close this hot Jupiter is to its parent star; it completes a single orbit happens in roughly one Earth day. The proximity also bestows some intriguing effects. Wasp 12b is tidally locked for one, the same side always facing the star. The temperatures on its day side are around 2,500ºC. This means that no molecules are able to form in its atmosphere, so there are no clouds to reflect the intense starlight from Wasp 12 back into space; it’s likely that all of its light is absorbed deep into the planet and converted to heat.
It’s this miniscule amount of reflection that’s the reason why Wasp 12b is the darkest of exoplanets known. Looking at the intense blackness of the world’s night side, it seems like a planetary sized lump extracted out of a mighty black hole using a cosmically scaled ice cream scoop.
The closeness of Wasp 12b’s star also means that there’s a merciless gravitational pull upon the planet, distorting it into an obvious oval shape and steadily stripping away its materials. It is disturbing to witness the bizarre events playing out for this planet close up, yet it’s completely arresting too.
It evokes the feeling you’d get watching some hapless creature that ambled too close to a mantis-like ambush predator. Now it’s locked into a destiny it cannot escape, being slowly consumed. Or perhaps it’s like a planetary indigestion pill slowly dissolving and effervescing until its eventual disappearance.
It’s all rather sad in a way: my trip in the Perihelion back to our backwater of the Milky Way feels like it’s being conducted in a minor key. Next time, I think a place of soothing planetary harmony is required.