All of which bodes well for those of us who would love for there to be extraterrestrial life out there somewhere.
On the other hand, of the exoplanets we've found, a great many of them are inhospitable to say the least, and some of them are downright bizarre. Here are a few of the weirder ones:
- TrES-2b, which holds the record as the least-reflective planet yet discovered. It's darker than a charcoal briquet. This led some people to conclude that it's made of dark matter, something I dealt with here at Skeptophilia a while back. (tl:dr -- it's not.)
- CoRoT-7b, one of the hottest exoplanets known. Its composition and size are thought to be fairly Earth-like, but it orbits its star so closely that it has a twenty-day orbital period and surface temperatures around 3000 C. This means that it is likely to be completely liquid, and experience rain made of molten iron and magnesium.
- PSR J1719−1438, a planet orbiting a pulsar (the collapsed, rapidly rotating core of a giant star), and therefore somehow survived its host star going supernova. It has one of the fastest rates of revolution of any orbiting object known, circling in only 2.17 hours.
- V1400 Centauri, a planet with rings that are two hundred times wider than the rings of Saturn. In fact, they dwarf the planet itself -- the whole thing looks a bit like a pea in the middle of a dinner plate.
- BD+05 4868 Ab, in the constellation of Pegasus. Only 140 light years away, this exoplanet is orbiting so close to its parent star -- twenty times closer than Mercury is to the Sun -- that its year is only 30.5 hours long. This proximity roasts the surface, melting and then vaporizing the rock it's made of. That material is then blasted off the surface by the stellar wind, so the planet is literally evaporating, leaving a long, comet-like trail in its wake.
Today, though, we're going to look at some recent research about a planet that should be near the top of the "Weirdest Exoplanets Known" list. It's 55 Cancri Ae, the innermost of four (possibly six; two additional ones are suspected but unconfirmed) planets around the star 55 Cancri A, a K-type orange star a little over forty light years away. 55 Cancri Ae orbits its host star twice as close as Mercury does the Sun, making a complete ellipse around it in only a bit under three days. This means that like CoRoT-7b and BD+05 4868 Ab, it's crazy hot.
This is where some new research comes in. A presentation at an exoplanet conference in Groningen, Netherlands last week considered a puzzling feature of 55 Cancri Ae -- a measure of its heat output shows odd, non-cyclic fluctuations that don't seem to be in sync with its orbital period (or anything else). The fluctuations aren't small; some of them have approached a 1,000 C difference from peak to trough. They were first detected ten years ago, and physicists have been at a loss to account for the mechanism responsible.
But now, we might have an explanation -- and it's a doozy. Models developed by exoplanet astrophysicist Mohammed Farhat of the University of California - Berkeley found that the anomalous temperature surges could be explained as moving hotspots.
Which sounds pretty tame until you read Farhat's description of what this means. We're talking about a planet close in to a star not much smaller than the Sun, being whirled around at dizzying speeds. This means it's experiencing enormous tidal forces. The planet itself is so hot it's probably liquid down to its core. Result: tidal waves of lava several hundred meters high, moving at the speed of a human sprinter.
The presentation definitely got the attendees' attention. "This is right in the sweet spot of something that is interesting, novel, and potentially testable," said planetary astronomer Laura Kreidberg, of the Max Planck Institute for Astronomy. "I had this naïve idea that lava flows were too slow-moving to have an observable impact, but this new work is pointing otherwise."
The whole thing reminds me of the planet Excalbia from Star Trek, from the episode "The Savage Curtain," which was completely covered by churning seas of lava -- except for the spot made hospitable by some superpowerful aliens so Captain Kirk could have a battle involving Abraham Lincoln, Genghis Khan, and various other historical and not-so-historical figures to find out whether good was actually stronger than evil.
Put that way, I know the plot sounds pretty fucking ridiculous, but don't yell at me. I didn't write the script.
In any case, I doubt even the Excalbians would find 55 Cancri Ae hospitable. But it is fascinating. It pushes the definition of what we even consider a planet to be -- a sloshing blob of liquid rock with lava waves taller than a skyscraper. Makes me thankful for the calm, temperate climes of Earth.
The universe is a scary place, sometimes.
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