All Space Considered, December 2015 (Exoplanets and Stars)

Exoplanet Formation Imaged

In the past decade or two, we've been finding exoplanets like crazy.  Despite what you may have heard about Kepler's discoveries, there are almost 2,000 confirmed exoplanets with absolutely no slowdown in the discovery rate in sight.  Though Kepler has been hobbled somewhat, the mission scientists and engineers have kept it fairly productive through very innovative and ingenious methods.  Additionally, NASA has a swanky new exoplanet-hunting satellite scheduled for launch next year, TESS.

The big news this month is that we actually imaged a planet forming.  This is the photo released to the press.

This is the LkCa 15 system.  You can see the star's protoplanetary disk on the left.  On the right, you see the planets up close.  While it may not look like much, what's important here is that a particular emission line from planet b shows that lots of material is falling onto it.  That process causes a lot of heat, creating ions that wouldn't be there otherwise.  Those ions are generating the emission line that is strong enough to indicate actual accretion occurring in this very picture.

Most Earth-like Exoplanet Not Very Habitable

Once an exoplanet is confirmed, various factors are used to create an Earth Similarity Index.  Kepler 438b has so far scored highest ESI at 0.88 (1.00 being identical to Earth in the criteria).  Unfortunately, research has shown that it's just too darn close to its host star.  While its proximity to its host star does put it in the Goldilocks Zone, the host star is a red dwarf.  These stars tend to be more active and Kepler 438 is no exception.  A team measured its activity and found that every few hundred days, Kepler 438 lets off a superflare.  The energy of each of Kepler 438's superflares is stronger than the most powerful ones ever recorded of our sun.  These generally lead to coronal mass ejections, which would more likely than not strip Kepler 438b of its atmosphere.  The study's authors did point out that if Kepler 438b has a strong magnetic field, then perhaps it could be shielded from the worst of the coronal mass ejections; however, they did not comment on how likely such shielding is.  Generally speaking, however, it isn't very likely.  If the planet formed that close, it would likely have tidally locked to the star, not leaving much room for the creation of a dynamo strong enough to repel the host star's stellar wind.

Supermassive Stars Shed Material

Observations of VY Canis Major, one of the largest stars in our Milky Way, have shown it shedding material before going supernova.  What's unique about the findings of the recent observations is that the dust grains being shed are larger than previously thought.  It was always theorized that the radiation pressure from the star itself would push the material it sheds outwards.  However, this pressure is very small and can only push material outward fast enough to escape the eventual supernova if the grains are of sufficient size.  The grains found are about 50 times larger than typical interstellar dust.  The other significance of this finding is that such large grains can actually survive the supernova itself, explaining some of the abundances of material in nebulae that we see.

I like the ESO's sense of humor with the title of their news release: Aging Star's Weight Loss Secret Revealed.  The above picture shows VY Canis Major through the eyes of a coronagraph.  The central circle that blocks the light from the star itself allows much more detail of the surrounding to be seen.

Low Metallicity Stars In Milky Way

The abundance of metal in a star can generally be used to age the star.  The less metal it has (in astronomy anything other than hydrogen and helium is a "metal"), the older it is.  This is because stars are creating new elements, first fusing hydrogen to helium, then helium to heavier elements and on up the periodic table.  As time goes on, these elements get cast out into the Universe, helping seed future generations of stars.  The later the generation a star belongs to, the more metal-rich it will be on average.  The general trend in the Milky Way is that older stars are at the edges and younger stars are closer to the center.  This stands to reason since star formation tends to be more frequent in denser areas.

However, the central bulge of the Milky Way is a difficult thing to observe.  There's so much stuff, it's hard to see what's going on.  With careful analysis of some data from the Gemini North telescope, it's been determined that there are a lot of old, low-metallicity stars close to the center of the Milky Way.  This bucks the observational trend, which means it bucks the current theories of how the Milky Way formed.  Chances are pretty good these low-metallicity stars came from a globular cluster or small galaxy that the Milky Way ate some time in the distant past.  However, much more evidence would need to be gathered to state this conclusion with any certainty.

All Space Considered, December 2015 (Our Solar System)

I've realized that I've gone a bit overboard in my desire to connect everything we're looking for in space to the possibility of life there.  While that is a tantalizing possibility introduced by most space research, there are lots and lots of other reasons to explore space too, not the least of which is sheer curiosity.  I'll try and tone the connection to life down a bit, though there may be reason to bring it up on occasion.

Pluto

Since its closest approach to Pluto in July, New Horizons has taken most of the headlines when it comes to solar system exploration; and does so with good reason.  It has improved our understanding of Pluto literally millions of times over.  Alan Stern, the mission's Principal Investigator, told an All Space Considered audience earlier in the year that our previous best images of Pluto couldn't resolve a continent and New Horizons would be able to resolve features just 10s of meters across.  For various engineering reasons, the images of highest resolution are just arriving now.  Here's one of the many stunners.

Since All Space Considered happened, a color version of the above photo (taken from this press release) has been released.  This really illustrates the contrast in geography on Pluto.  To this non-expert, it seems pretty clear the surface is undergoing major changes on a pretty regular basis.  Apparently, to many trained experts, some of the pictures seemed to indicate icy volcanoes on Pluto.  Some features resembling shield volcanoes on Earth were seen in some of the images.  In the words of Oliver White, a researcher at NASA's Ames Research Center, "Whatever they are, they're definitely weird.  Volcanoes is the least weird hypothesis at the moment."  For more details, see this article at space.com.

Titan (Saturn's largest moon)

This moon of Saturn has become a favorite of mine.  Between its size (10th biggest object in the entire solar system), thick atmosphere, rocky terrain, standing lakes of methane and salty subsurface water oceans, it has a level of complexity and strangeness I personally find matched only by Earth.  Some new images of Titan came back from Cassini and, as usual, we saw something we didn't expect.  Here it is.

Titan seems to have a belly button.  That belly button is actually a cloud formed during the transition of Titan's south pole from fall to winter.  We're watching seasons change ON ANOTHER FRICKING PLANET!  There's a full(er) explanation of the whole phenomenon in NASA's press release.  My favorite tidbit is that the clouds form by subsidence (new vocab word for me).  For reasons beyond my understanding, warm gases sink in Titan's atmosphere.  As the warm gases from the northern hemisphere circulates to the colder, southern hemisphere, the sinking takes them through progressively colder surrounding temperatures.  Different gases will condense out at different altitudes, forming clouds along the way.

Phobos (Mars's largest moon, for now)

Mars's largest moon, Phobos, has some funny geological features.  In the picture below, they can be see as striations emanating from the large crater in the lower right.  After lots of analysis, it's been discovered that Mars is pulling Phobos apart.  Tidal forces from Mars's gravity is causing Phobos to stretch enough to cause the fracturing and cracking that is seen here.  This is a bit of a happy accident, as Phobos is surprisingly light.  Its density is only about 1/3 that of Earth or about 60% that of the moon.  This means it's easier for tidal forces to act on it, especially at the fairly close distance Phobos is to Mars.

Based on all this data, it appears that Phobos will be ripped apart in 20 to 40 million years.  On human scales, that's a pretty long time, but on astronomical scales, that's pretty soon.  Also, in the intervening time, we can keep looking at Phobos.  What's really cool about this is that when Phobos breaks apart, it may form a ring around Mars.  It's suspected some of the inner planets may have had rings in the past, when the structures and material in the solar system were much more dynamic.  It would be cool if one of the inner planets could join the gas giants in having a ring.

Nuclear Fusion? Maybe, maybe ...

We're trying to make stars on Earth.  Luckily for everyone's weight, there isn't enough mass on Earth to make a star the usual way, via gravity.  Instead, we're trying to initiate fusion in a controlled manner, the true holy grail of clean energy for many decades.  Fuel for fusion is abundant and safe and the waste byproducts require far less special care than their fission counterparts.  The standard joke about fusion is that it's always 50 years away.  While true in some sense, people who actually work on fusion would tell you that it's been $80 billion away for decades.  I always like to show this graphic made by Geoff Olynyk when "fusion will always be decades away" rears its ugly head.

Way back in 1976, these were the projections for when we might have fusion given various levels of funding.  Even then, they had the humor to label the projected 1978 level of funding "fusion never."  While I tend to take graphs like this with a grain of salt (predicting the future is hard), the absolutely dreadful level of actual funding is far more astonishing to me.  Do you know how little money $80 billion spread over 15-30 years is compared to a decades-long Cold War?

Hyperbole aside, I let fusion lapse from my attention a bit.  From the "NUCLEAR BAD!!!" camp to the "That's science fiction" to the blank stares, it just didn't seem like the collective fortitude required to attain fusion was there.  I also saw that ITER, the main tokamak project in the world right now, was having difficulties, technical, economic and political.

Then, along came Weldenstein 7-X (W 7-X).  Not being a nuclear engineer nor having quite the time to delve fully into all the tokamak alternatives, I didn't even know what a stellerator was a few months ago.  Glossing over many details, I think Thomas Klinger, the Scientific Director of W 7-X, put it best.  "They are both terrible beasts.  Our's [stellerator] is a beast to build; your's [tokamak] is a beast to operate."

A tokamak is basically a giant magnetic donut.  Intense magnetic fields confine a plasma hot enough to initiate nuclear fusion.  The big problem: the plasma wants to radiate outwards from the center, forcing tokamak designers to jump through all kinds of hoops to keep it on its circular path.  A stellerator, on the other hand, is ... is ... well ... hard to describe.  Here's a picture.

You can go to ScienceMag, where I got this picture from, for further details.  The idea is to fight the outward radiation that tokamaks contend with by making the plasma twist around as it "orbits."  In my completely non-expert understanding, just when the plasma wants to go off course, you twist the course so it comes back in, which results in the weird, twisty thing pictured above.  W 7-X just turned on for the first time Thursday (Dec 10).  It did everything it was supposed to do and the project participants are pleased as punch.  Even if W 7-X performs exactly as designed for the remainder of the project's duration, it still won't generate commercial levels of energy.  However, it is an important research platform and demonstration of fusion's potential as a clean energy source.

I really hope some form of fusion finally makes its way to commercial usage eventually.  We have enough fuel on Earth to produce energy at current levels for millions of years and that fuel (heavy water and lithium) is in places we don't have to fight wars to secure.   If this really works and does so soon enough, perhaps the inaction at the Paris climate talks won't matter.