Hot Jupiters Exasperate Astronomers

Nothing has been more upsetting to comfortable theory than the discovery of hot Jupiters around other stars.

It’s nice to find an honest astronomer not predisposed to triumphalism. Astrophysicist Paul Sutter is such an one. In his Space.com piece, “Extremely Hot and Incredibly Close: How Hot Jupiters Defy Theory,” he writes as if a humiliated penitent in a confessional. His article should send a warning to scientists who tend to be overconfident in their knowledge and methods.

As usual, we thought we had it all figured out. See that gas giant over there in the outer solar system? It was born there. It will spend its whole life there, and it will die there. Sure it might wiggle around a bit every few hundred million years — who doesn’t? — but, by and large, planets don’t move.

Surprise: Planets move. And not just a little. They move a lot. All over the place. In fact, in the early days of a solar system’s formation, planets are a little rambunctious: squirrely little toddlers jostling about underfoot. But it wasn’t until we started observing planets in other solar systems (“extrasolar planets” or “exoplanets” for the astronomer on the move) that we really noticed this fact. 

The hot Jupiters, in particular, put shame on the face of planetary scientists whose models went kaput with the discovery of these fast-moving giants. The penitent weeps:

And it wasn’t just any type of exoplanet that kicked off this re-think; it was the hot Jupiters. Imagine: a planet more massive than the largest one in our solar system and 10 times warmer, a monstrous beast of hydrogen and other elements, complete with swirling bands of gas and a rich, dynamic atmosphere, orbiting closer its star than Mercury orbits the sun. In some solar systems, such a planet orbits so quickly that its year is shorter than the Earth’s day. That means these worlds can whip around their parent stars in hours. The physics involved can reduce the most hardened scientist to tears.

Dr. Sutter tries to regain his composure. Maybe a little humor will help.

When astronomers spotted the first hot Jupiter (51 Pegasi b, the first exoplanet to be found around a sunlike star, no less), the reaction was mostly, “Ha ha, mother nature, that’s cute. You got us this time, but no more funny business, OK?”

But then another hot Jupiter was found. And another. Then half a dozen more. They went from goofy oddballs to … normalcy. For a while, it started to look like our own solar system was the weird one. Maybe they should just be called “regular Jupiters,” and ours re-named a “cold Jupiter?”

The tears flow again, as Sutter recalls astronomers having our own solar system all worked out: rocky planets inside the frost line, gas giants outside the frost line. It had to be that way. That’s what made sense. Our own solar system was proof of it.

Sutter dispenses with the notion of a selection effect: i.e., that because hot Jupiters are easier to detect, we overestimated their abundance. No; they’re there—plenty of them. We see a broader range of sizes and distances now, but how can astronomers explain the hot Jupiters that should not exist? Sutter backslides into the besetting sin of ex-post facto modeling with ad hoc conditions to fit the observations, stated with bravado:

The best guess we have so far — and it really is a guess at this point — is that a Jupiter-like planet forms in an appropriately Jupiter-like orbit in an early gaseous, nebulous not-quite-a-solar-system. The big world clears a gap in the gaseous disk, because that’s what giant planets do. It’s stuck to the middle of the gap like a car on a racetrack. If it moves too close in, the bands of gasses around the star are rotating faster than the planet is orbiting, and so nudge the giant young planet back out. If the planet scoots out too far, the slower-moving gas bands located there nudge it back into its proper place.

But since the system is so young, it’s not done contracting and compressing. The gas continually brushes against the planet, playing a fantastically huge game of curling to keep the planet within the gap. And as the entire disk of gas continues to squeeze inward to its final, compact size, it carries the gap — and the newly formed planet — with it. Voilà: a Jupiter-size planet in the inner solar system!

That’s all an act. The solution breeds numerous new questions, he notes, that are just as hard to answer. He confesses, “honestly, the whole mechanism seems a little dodgy, if you ask me.” To show this is not just Sutter’s millstone, Jeff Hecht expressed similar heaviness in his piece “The truth about explanets” in Nature:

Little more than two decades after the first planets were found orbiting other stars, improved instruments on the ground and in space have sent the count soaring: it is now past 2,000. The finds include ‘hot Jupiters’, ‘super-Earths’ and other bodies with no counterpart in our Solar System — and have forced astronomers to radically rethink their theories of how planetary systems form and evolve.

Meanwhile, Sutter ignores his confessor’s advice to take up truck driving. “To solve this riddle, we have to do what scientists do best: think about it some more. And more data wouldn’t hurt, either.”

Good grief, Dr. Sutter! Your materialist friends have been thinking about it since Descartes and Laplace! How much more time does the public owe you? In any other career you would all be bounced out the door as losers. Thanks for the honesty, but have you ever thought along different lines? i.e., that your presuppositions might be in error? Please watch this and this.

Our readers will recognize a familiar pattern: chutzpah humiliated by reality. It happened all over our solar system. Every planet they visited  (including Pluto, the latest) turned out to be totally different than what the “experts” thought. Now it’s happening again around hundreds of other star systems. Astronomers’ skill at getting there and observing is top notch; their skill at explanation, though, is pretty sorry. When data hurts, it might be an indication you crash landed onto the planet.