Astronomers are hoping a recently discovered planet is on a rare suicidal orbit around its parent star. If it isn’t, the entire basis on which they make calculations about orbits may have to be rewritten.
WASP-18b is around 325 light years away from Earth: though that’s 1,885 trillion miles, it effectively makes it a close neighbor in the context of space as a whole. It takes its name from from the Wide Angle Search for Planets project which discovered it; the project’s cameras are pictured right.
The planet is only 1.9 million miles from its star, WASP-18, less than a twentieth of the distance between our Sun and its closest planet, Mercury. WASP-18b orbits in the equivalent of 22.5 hours (Earth time), quicker than the time it takes the planet to spin round. That means that by all astronomic logic, it should be moving closer and closer to its parent star.
However, given that WASP-18b being so close to the star means it must be around 3,800 degrees Fahrenheit, and taking into account that it is ten times the size of our solar system’s largest planet (Jupiter), its lifespan should only have been about a million years before being burned up. As WASP-18 is around a billion years old, and planets usually form around the same time as parent stars, something is amiss.
Douglas Hamilton, an astronomer who wrote a commentary on the report into the planet, told the LA Times that even the main possible explanations have flaws. It could be that WASP-18 has much less energy than assumed, causing less orbital drag; however, that would mean astronomers had overestimated the energy by a factor of a thousand, raising serious questions about standard assumptions.
It may also be that the planet has only recently been knocked into its current position, though in the big picture that would make it an amazing coincidence that astronomers spotted it before it met its doom.
According to Hamilton, that may leave one other explanation: “Perhaps we really are missing some key bit of physics.”