When it comes to the different kinds of planets out there, orbiting other stars in our galaxy, and in our universe, it’s easy to imagine our mix of planets as being pretty standard. But the more likely scenario is that it doesn’t even scratch the surface. There have to be all kinds of weird planets out there. Take the exoplanet WASP-12b for example, a planet darker than fresh asphalt.
12b, located in a system about 1,400 light years from our solar system, is one of the coolest (by which I mean hottest) and most alien-sounding planets researchers have yet found.
The planet is categorized as a “Hot Jupiter” type planet. It’s a gas giant, relatively close in size to our own planet Jupiter, but it orbits its sun much, much more closely. Our planet rotates around the sun at about 1AU (astronomical unit), while the closest planet in our system, Mercury, rotates the sun at about 0.39AU. WASP-12b, in comparison, rotates at just 0.0229AU. A complete rotation of the sun – a year, in other words – takes 12b just under one earth day.
Too hot for TV (and metal, and hydrogen)
The planet was studied by researchers at the Institute for Research on Exoplanets and McGill University (IREx) using the Hubble Space Telescope Imaging Spectrograph.
The side of 12b facing the sun is a downright balmy 2811 degrees Kelvin – that’s about 4600°F. That’s hot enough to boil copper. Another, closer so-called Hot Jupiter, WASP-19b, shows traces of titanium oxide in its atmosphere, so that’s not a wild idea. The dark side is a much cooler 2000°F, or about 1366 K.
The team watched the planet as it traveled behind the sun at the center of its system, and they observed something really interesting: this planet doesn’t reflect very much light. The sun-facing side of the planet is so hot that most molecules can’t survive, so clouds don’t form, and hydrogen molecules break up into atomic hydrogen. The atmosphere is closer to that of a star than a planet.
All of this leads to extremely low reflectivity, a measurement called albedo. Earth has a 0.3 albedo, while our Moon’s is 0.12. That’s about two times more reflective than 12b, which has an albedo of just 0.064. The planet, says lead researcher Taylor Bell, is “darker than fresh asphalt.”
Space is wild, and we haven’t even dipped our toes in yet.