Astrophysicists Find "Impossible" Planet

SpuriousLogic writes "Scientists have discovered a planet that shouldn't exist. The finding, they say, could alter our understanding of orbital dynamics, a field considered pretty well settled since the time of astronomer Johannes Kepler 400 years ago. The planet is known as a 'hot Jupiter,' a gas giant orbiting the star Wasp-18, about 330 light years from Earth. The planet, Wasp-18b, is so close to the star that it completes a full orbit (its "year") in less than an Earth day, according to the research, which was published in the journal Nature. Of the more than 370 exoplanets — planets orbiting stars other than our sun — discovered so far, this is just the second with such a close orbit. The problem is that a planet that close should be consumed by its parent star in less than a million years, say the authors at Keele University in England. The star Wasp-18 is believed to be about a billion years old, and since stars and the planets around them are thought to form at the same time, Wasp-18b should have been reduced to cinders ages ago."

Comments

Nature paper

[petaflop]

Nature paper here. Interesting quote:

For comparison, WASP-18b's infall timescale is an order of magnitude shorter than that of the much-discussed OGLE-TR-56b6, 7 (assuming that Q is the same for both), and gives a current rate of period change of â"0.00073 (106/Q) s/yr. For low values of Q this would accumulate to a detectable change in transit epoch in less than a decade (for Q = 106 the transit time shifts by 28 s after 10 yr, which compares with a currently achievable timing accuracy of 5 s). Thus WASP-18b is a diagnostic planet, either (for a low Q) being an exceptionally rare object in which the tidal decay is directly measurable, or forcing a reappraisal to much higher Q values; either way it will help establish the dynamical ages of the class of hot-Jupiter planets. WASP-18 will also help constrain our understanding of stellar interiors, given that the Q value depends on the dissipation of interior waves excited by the tidal forcing.

So if the orbit is decaying, we'll be able to measure it in 10 years, otherwise there will be useful data to refine theories about tidal forces in the surfaces of stars.

Maybe it was a "normal" planet...

[Osvaldo Doederlein]

...formed one billion years ago, but originally much more distant from the star. But its orbit was not stable, approaching quickly (in astronomical time) to the star; and we're just lucky to have found it in the final stage of the death spiral. If this is the case, it may even be possible to watch the final spectacle in a timeframe reasonable for human scale (a few thousand years, perhaps centuries, or even less).

Wild speculation of course... but just to be safe, I'm immediately canceling all my plans of space vacations near the Wasp18 system. I never liked wasps anyway.

alternatively

[circletimessquare]

we're actually watching the planet in the process of being consumed

which would be highly unlikely, to get that timing right, as there's a window of only a couple thousand years in which we could see that happen, but maybe that's what we're really seeing

in which case, rather than revise orbital dynamics, this planet could contribute to our understanding of astrophysics/ michael bay style thermodynamics by allowing us to watch a jupiter sized planet ripped to smithereens in real time

Re:Maybe the measurements are wrong or incomplete

[OrangeTide]

Note to Slashdot admins: A DROPDOWN BOX IS A VERY VERY STUPID MECHANISM FOR MODERATION. That is all.

Yea! Why isn't it command-line based like other good user interfaces?

Re:Quick Call the Doctor

[smellsofbikes]

Actually, I thought about your point when the show aired. In fact, it is impossible for that planet to exist. You can't form a long-term stable orbit around a black hole. From a two-body, Newtonian point-mass analysis, yes the planet can exist. However, a planet that close to a black hole will be affected by Einstein's General Relativity, which predicts a collapsing orbit. Additionally, the planet would be experiencing severe gravitational stresses and magnetic stresses, causing it to break up or its orbit to decay. The other matter collapsing into the black hole would disrupt the "stable" orbit, also causing the planet's orbit to decay or it to break up. In short, I don't think that it is possible to have a long-term stable orbit around an black hole when it is consuming matter.

Okay, I'll bite. What's the difference between a black hole and any other star, from a reasonable distance? A black hole's just a mass, that within a certain distance of the black hole (the Schwarzschild radius) acts very oddly indeed, but outside that distance, acts like any other large mass. A black hole could have the same mass as the Earth (but be the size of a golf ball) and the moon would still orbit it just fine, wouldn't it? It seems to me the main problem the planet would have is that a black hole would be, well, black, so the planet would be as cold as Pluto.