The tide is high

The list of confirmed exoplanets now exceeds six thousand.  Considering the fact that the three main ways they're detected -- direct measure of stellar wobbles, transit photometry, and Doppler spectroscopy -- all require either that the host star be close, that the planets be massive, or that the planetary orbit be aligned just right from our perspective, or all three, it's almost certain that there are vast numbers of exoplanets going undetected.

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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The dynamic Earth

The highlight of my trip to Iceland this past August was seeing the newly-erupting volcano of Fagradalsfjall, southwest of the capital city of Reykjavík.

Fagradalsfjall is Icelandic for "mountain of the beautiful valley."  I'm not sure I'd use the word "beautiful," which to me carries connotations of "benevolent."  When we were there, you could feel the eruption before you heard or saw it; the entire floor of the valley was vibrating, a subsonic rumble that I felt in my gut.  Then you hear the roar, a guttural, low-pitched thunderous booming.  Then you smell it -- the characteristic sulfurous, rotten-egg smell of an active volcano.  Then you crest the top of a low hill, and see it for the first time.

We were close enough that we could feel the warmth radiated from the lava.  Much closer, and the combination of the heat and the sulfur gases would have been overwhelming.  Orange-hot plumes of molten rock exploded out of the fissure and splattered onto the sides of the cinder cone, almost instantly turning to shattered, jagged chunks of black basalt as it cooled and hardened.

It was one of the most spectacular things I've ever witnessed.  In the presence of this kind of power, you truly feel tiny and very, very fragile. 

We were really extraordinarily lucky to see what we did; we were there on the 15th of August, and -- for reasons unknown -- the eruption abruptly ceased on the 21st.  Fagradalsfjall is still very much an active volcano, though.  Just last week it started up again, and this cycle looks like it may actually be even more dramatic.

What brings all this up is a paper last week in Nature about some research out of the University of California - Santa Barbara that analyzed the lava from Fagradalsfjall and found that it ran counter to the conventional model of how volcanoes erupt.  The previous understanding was that magma chambers fill gradually, and undergo mixing from convection and the physical shaking from earthquakes; then, when the eruption happens, the chamber drains.  This would result in a relatively uniform chemistry of the rock produced from the beginning of the eruption to the end.

That's not what geologists saw with Fagradalsfjall.

"This is what we see at Mount Kilauea, in Hawaii," said Matthew Jackson, who co-authored the study.  "You'll have eruptions that go on for years, and there will be minor changes over time.  But in Iceland, there was more than a factor of 1,000 higher rates of change for key chemical indicators.  In a month, the Fagradalsfjall eruption showed more compositional variability than the Kilauea eruptions showed in decades.  The total range of chemical compositions that were sampled at this eruption over the course of the first month span the entire range that has ever erupted in southwest Iceland in the last 10,000 years."

Why this happened is uncertain.  It could be that Fagradalsfjall is being fed by blobs of liquid magma rising from much deeper in the mantle, where the chemistry is different; those much hotter blobs then rose to the surface without a lot of mixing, resulting in a dramatic alteration of the rock being produced over the course of the eruption.  This adds a significant complication to interpreting records of past eruptions, not only in Iceland, but with other volcanoes.

"So when I go out to sample an old lava flow, or when I read or write papers in the future," Jackson said, "it'll always be on my mind: This might not be the complete story of the eruption."

It's fascinating that as far as science has come, we still have a lot to work out -- not only out in the far depths of space (as yesterday's post about MoND described) but right beneath our feet on our own home world.  As eminent astrophysicist Neil de Grasse Tyson put it, "You can’t be a scientist if you’re uncomfortable with ignorance, because scientists live at the boundary between what is known and unknown in the cosmos.  This is very different from the way journalists portray us.  So many articles begin, "Scientists now have to go back to the drawing board."  It’s as though we’re sitting in our offices, feet up on our desks—masters of the universe—and suddenly say, "Oops, somebody discovered something!"  No.  We’re always at the drawing board.  If you’re not at the drawing board, you’re not making discoveries."

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