Sciency Words: Syzygy

Hello, friends!  Welcome to Sciency Words, a special series here on Planet Pailly where we take a closer look at the definitions and etymologies of scientific terms.  Today on Sciency Words, we’re talking about the word:


We’ve all seen pictures like this, with all eight planets lined up in a row:

And sometimes, on extra special occasions, the planets really do line up like that, or at least they come very close to it.  When this happens, we call it a grand syzygy.

The word syzygy traces back to ancient Greek.  It originally meant “yoked together,” as in: “The farmer yoked together his oxen before plowing the field.”  According to my trusty dictionary of classical Greek, the word could also mean “pair” or “union.”

Some closely related words in Greek referred to balance, teamwork, sexy times, etc.  And our modern English words synergy and synchronized have similar etymologies.  Basically, what all these words have in common is a sense of people or things coming together, in one manner or another.

For modern astronomers, syzygy means three or more celestial bodies coming together to form a straight line.  The most commonly cited example of this is the alignment of the Sun, Earth, and Moon that occurs during either a new moon or full moon, as observed here on Earth.

But an alignment doesn’t have to be perfectly straight to be called a syzygy, especially when we’re dealing with more than three objects.  According to this article from The New York Times, a syzygy of the Sun, Venus, Earth, Mars, Jupiter, and Saturn occured between March 25 and April 7, 1981.  The Sun and five planets came “within 2 degree of arc from a perfect straight line.”  Apparently that’s close enough.

But while that 1981 syzygy was pretty grand, it was not the grandest of grand syzygies.  The planets Mercury, Uranus, and Neptune were left out.  According to another article from The News York Times, a truly grand syzygy will happen on May 19, 2161, “[…] when eight planets (excluding Pluto) will be found within 69 degrees of each other […].”

So mark your calendars, friends!  You don’t want to miss the grand syzygy of 2161!

P.S.: And if you’re a Star Trek fan, you may recall that 2161 will be an auspicious year for another reason.  That’s the year when the United Federation of Planets will be founded—a political syzygy, one might say, occurring at the same time as an astronomical syzygy.

Sciency Words: Barycenter

Hello, friends!  Welcome to Sciency Words, a special series here on Planet Pailly where we talk about those big, complicated words scientists use.  Today’s Sciency Word is:


Excuse me, but I’m going to do that “um, actually” thing that people who think they’re really smart like to do.  Now you may think the Earth orbits around the Sun.  Um, actually… the Earth and Sun both orbit something called the barycenter.

The word barycenter comes from two Greek words meaning “heavy” and “center,” and it refers to the common center of mass for two or more celestial bodies.  Based on sources I found via Google Ngrams, the term started appearing frequently in astronomical journals during the early 20th Century, and it may have been in use as early as the 1880’s.

Let’s say you have two celestial bodies.  One is really massive, the other is much less massive.  In that case, the barycenter will probably be located somewhere inside the more massive object.  This is the case for the Earth and her Moon.  Based on numbers I got from Wikipedia, the Earth-Moon barycenter is about 1000 miles (1700 km) beneath Earth’s surface.  Or to measure that a different way, the barycenter is about 3000 miles (4600 km) away from the center of the Earth.

Now let’s say you have two celestial bodies of roughly equal mass.  In that case, the barycenter will be located somewhere between them.  Something like this has happened with Pluto and his giant moon, Charon.  Once more using numbers from Wikipedia, it looks like the Pluto-Charon barycenter is about 500 miles (960 km) ABOVE the surface of Pluto.

As for the Earth-Sun barycenter, it’s located deep inside the Sun.  So if you say Earth orbits the Sun, you’re not too far from the truth.  But of course Earth is not the only planet in the Solar System, and when you consider the Solar System as a whole, you’ll find the Sun wibbles and wobbles about in weird, loopy patterns.  As you can see in the highly technical diagram below, the Sun wibbles and wobbles so much it can wobble into a totally new position in just a few years.

Click here for an actual diagram of the Sun’s movement relative to the Solar System’s barycenter.

As explained in this paper, this is mainly due to the gravitational influences of Jupiter and Saturn. Over longer time scales (centuries rather than decades), the subtler influences of Uranus and Neptune also have a noticeable effect.

So the next time someone tells you the Earth orbits the Sun, you can do the “um, actually” thing and explain what a barycenter is.  Trust me, it’s a great way to sound smart and make lots of new friends!

Next time on Planet Pailly, what did people in 1962 think we’d find on other planets?

The Great Red Spot: More Than Skin Deep?

You and I may think of the Great Red Spot as Jupiter’s defining characteristic, but Jupiter himself is rather embarrassed about his spot.  He’s been trying for some time now to get rid of it.

The Great Red Spot (or G.R.S., as all the cool kids call it) has been shrinking for decades now, and the rate of shrinkage has been accelerating.  Just this year, long streams of red stuff seemed to break free, as it the G.R.S. were “unspooling.”

So why has the G.R.S. gone into decline?  Well, a better question might be why did it last so long in the first place?  Apparently, according to most fluid dynamics models, the G.R.S. should have only lasted a few years.  Instead, it’s been going strong for centuries.  Astronomers first noticed it as early as 1664.

In 2013, physicists Philip Marcus of U.C. Berkley and Pedram Hassanzadeh of Harvard gave us a partial answer.  According to this article from, they were the first to model the G.R.S. not as a 2D surface feature but as a 3D structure, with a vortex extending into the depths of Jupiter’s atmosphere.

Marcus and Hassanzadeh found that vertical flow (hot and cold air moving up and down inside the G.R.S.) was doing a lot to help keep the storm system going.  As Hassanzadeh explains in that same article:

In the past, researchers either ignored the vertical flow because they thought it was not important, or they used simpler equations because it was too difficult to model.

Late last month, Marcus and Hassanzadeh gave a presentation at the annual meeting of the American Physical Society, and according to that presentation, fans of the Great Red Spot have nothing to worry about.

As Marcus explains in this article for Astronomy Magazine, we can monitor the vortex beneath the G.R.S. by observing the behavior of other nearby storm systems.  And based on those observations, Marcus says, “[…] there is no evidence that that vortex itself has changed its size or intensity.”

Personally, I think Marcus and Hassanzadeh make a pretty compelling case that the G.R.S. is as strong as ever, even if it appears, superficially, to be shrinking.  But I still don’t really understand what’s caused that superficial shrinkage, and I’m left wondering how long it will be before the visible part of the G.R.S. starts to expand again.  Surely it will start expanding again, right?

I guess there’s always more to learn.

Quick, Name Those Moons!

I haven’t done enough research this week to put together a Sciency Words post.  I’ve been too busy with other writing.  However, I do have some name-related news to share with you today.

As you may have already heard, astronomers recently discovered twenty new moons orbiting the planet Saturn.  This brings Saturn’s total moon count up to 82, surpassing Jupiter’s total of 79.

These newly discovered moons are each about five kilometers in diameter, according to this press release from Carnegie Science.  That’s really small for moons.  These objects are more like asteroids that happen to be caught in Saturn’s gravity.  Or they might be rubble left over from the destruction of older Saturnian moons.  Saturn may (or may not) have a long history of destroying her own moons.

Now astronomers are asking for you (yes, you!) to help name these newly discovered moons.  Due to established naming conventions, these particular Saturnian moons must be named after giants from Inuit, Norse, or Gallic mythology.  Tweet your suggestions to @SaturnLegacy using the hashtag #NameSaturnsMoons.  Name submissions are due by December 6, 2019.

So go crack open some books on Inuit, Norse, and Gallic mythology, and may the best names win!

Sciency Words: Euphotic Zones

Sciency Words: (proper noun) a special series here on Planet Pailly focusing on the definitions and etymologies of science or science-related terms.  Today’s Sciency Word is:


Based on what Google ngrams has to tell me, it looks like “euphotic” and “euphotic zone” entered the English lexicon right at the start of the 20th Century, then really caught on circa 1940.

The word euphotic is a combination of Greek words and means something like “good lighting” or “well lit.”  In the field of marine biology, the euphotic zone refers to the topmost layer of the ocean, or any body of water, where there’s still enough sunlight for photosynthesis to occur.

My first encounter with this term was in this paper by astrophysicists Carl Sagan and Edwin Salpeter.  Sagan and Salpeter sort of co-opted this term from marine biologists and applied it to the layer of Jupiter’s atmosphere where—hypothetically speaking—Jupiterian life might exist.

I don’t see any reason why the term could not also by used for other planets as well.  There’s a euphotic zone just above the cloud tops of Venus.  The same could be said about Saturn or Uranus.  Or maybe if the ice is thin enough, we may find euphotic zones right beneath the surfaces of Europa or Enceladus.

Of course just because a planet has a euphotic zone, that doesn’t mean photosynthetic organisms are living there.  And also there are plenty of ecosystems here on Earth that do not depend on photosynthesis and that don’t exist anywhere near a euphotic zone.

Still, I’m very glad to have picked up this term.  The concept of euphotic zones can be very helpful in any discussion of where alien life may or may not be hiding.

Is This the End of the Great Red Spot?

I have sad news.  Right now, we may be witnessing the final death throes of Jupiter’s Great Red Spot.

For those of you who may not know, the Great Red Spot is an enormous storm that’s been raging on Jupiter for centuries.  It was visible to the telescope as far back as Galileo’s time, and it’s surely been around much longer than that.

But over the last few decades, the notorious G.R.S. has been slowly shrinking.  Recently, the rate of shrinkage has accelerated.  According to, the storm is 20% smaller than it was a month ago.  In the time lapse animation below, you can actually see giant blobs of red break free of the Great Red Spot and then disperse into Jupiter’s atmosphere.


Has the Great Red Spot suddenly reached a point where it can no longer sustain itself?  Or will the storm resurge and start to grow once more?  I don’t know.  At this point, I don’t think anyone knows.

But I would like to take this opportunity to pontificate a little on the value of space exploration.  Space exploration is expensive, and to many people it seems like a colossal waste of money.  Shouldn’t we be spending all that money trying to solve the problems we have here on Earth?

The thing is space exploration does help us solve our problems here on Earth.  Our ability to compare and contrast Earth with other planets has taught us so much!  Even Jupiter—about as un-Earth-like a planet as there can be—has added to our knowledge of how weather patterns form, sustain themselves, and change over time.

Whatever is happening to the Great Red Spot, this is an opportunity for us to learn.  I have no idea what we’re going to learn, but we’re going to learn something.  We’re going to know a little more about storms in general, which will help us refine our models about storms on Earth in particular.

Weather forecasts will improve.  Maybe we’ll be a little better at predicting hurricanes, and that, in turn, will save lives. All thanks to the space program and the Great Red Spot.

Sciency Words: Sinkers, Floaters, and Hunters

Sciency Words: (proper noun) a special series here on Planet Pailly focusing on the definitions and etymologies of science or science-related terms.  Today’s Sciency Word is:


In the 1970’s, Carl Sagan and fellow astrophysicist Edwin Salpeter were curious about the orangey-red coloration seen on certain parts of Jupiter.  That sort of orangey-red color is frequently associated with organic chemistry (see my post on tholin).

So in this 1976 technical report for NASA, Sagan and Salpeter hypothesize that we really are seeing organic compounds in Jupiter’s atmosphere.  They then go on to imagine what kind of life might develop on a planet like Jupiter.  As a frame of reference, they start by describing one specific example of life here on Earth:

The best analogy seems to be the surface of the sea.  Oceanic phytoplankton inhabit a euphotic zone near the ocean surface where photosynthesis is possible.  They are slightly denser than seawater and passively sink out of the euphotic zone and die.  But such organisms reproduce as they sink, return some daughter cells to the euphotic zone through turbulent mixing, and in this way maintain a steady state population.

So if microorganisms exist on Jupiter, perhaps they follow a similar lifecycle.

Sagan and Salpeter name these hypothetical microorganisms “sinkers,” since sinking is pretty much the defining characteristic of their lifecycles.  But if these sinkers really do exist, then Jupiter may be able to support other, more complex forms of life as well.

Sagan and Salpeter go on to describe “floaters.” Floaters would be giant organisms, perhaps several kilometers in radius.  In order to remain buoyant, they’d have to have very thin skin and be filled with a lifting gas like hydrogen.  Floaters would drift aimlessly through the skies of Jupiter, feeding on the rising and falling swarms of sinkers.

And then there would be “hunters,” as Sagan and Salpeter call them, though that term may be misleading.  Hunters would be able to maneuver deliberately through the air, “hunting” for other organisms.  But these hunters would not eat their prey, at least not in the way we understand eating.  Instead, through a process called “coalescence,” the hunter and the hunted would merge together as one giant super-organism.

Personally, I think Sagan and Salpeter let their imaginations run a little too wild in this paper.  Could life exist on Jupiter?  Sure.  The universe is full of possibilities.  Can we predict with any specificity what life on Jupiter would be like?  I doubt it.

Still, the Jovian ecosystem that Sagan and Salpeter described seems plausible enough.  For the purposes of science fiction, it deserves some attention, and it inspired the short story I posted on Monday.  However, if you haven’t read that story yet, I have to confess (spoiler warning): it turns out the planet in that story is not Jupiter.

Europa’s Cold Spot

I still have a ton of research reading to catch up on from 2018.  This weekend, I read a paper about Europa.  I wasn’t sure at first why this was on my to-be-read list, but by the end I knew why this one had caught my attention.

Europa is one of the icy moons of Jupiter.  It’s often listed as one of the most likely places in the Solar System where we might find alien life.  That’s because there’s evidence of a vast ocean of liquid water sloshing around beneath Europa’s icy crust.

Maybe someday we’ll be able to drop a little robo-submarine into that ocean and see if anything’s swimming around down there. But in the meantime, we’re really only able to explore Europa’s surface.  And as you can see in the highly technical diagram below, no matter where you go on Europa’s surface, it’s cold.  But in one specific region, Europa gets really cold.

Or at least, that one region appears to be extra cold.  This is a case where it’s important to understand how we get our data. We’re really measuring Europa’s thermal emissions, the amount of heat that gets radiated out into space. So that cold spot may represent one of two things:

  • Either that region absorbs less sunlight than the rest of Europa, and so it never heats up in the first place…
  • Or that region does a better job trapping the heat it absorbs from the sun, and so we detect less heat escaping back into space.

Either way, something weird is happening. Unfortunately, our previous missions to the Jupiter system did not provide us any useful photos of that one specific spot on Europa’s surface.  Our current Juptier mission, Juno, is unable to approach Europa at all, so that’s no help.

So we can’t match this anomalous cold spot to a visible surface feature.  However, the authors of the paper I read did suggest that this could be a sign of recent geological activity—the formation of chaos terrain, perhaps.

And if that’s true, we might (might!) find the waters of Europa’s subsurface ocean seeping up to the moon’s surface.  Maybe there’s fresh organic material seeping up onto the surface too.  Maybe.


Could be worth checking out, though.  Don’t you think?

My Favorite Moon: Io

Some of you may remember a post I did awhile back declaring Europa to be my favorite moon.  It’s a beautiful and mysterious world, a world that may have an incredible secret hidden beneath its icy crust.  Europa frequently tops the list of most likely places where we might find alien life.

But as I’ve learned more about the Solar System, I’ve developed a deeper affection for another moon, one of Europa’s neighbors, a world that is neither beautiful nor likely to support life.  I’m talking about Io.

Io is the innermost of Jupiter’s four big moons (Io, Europa, Ganymede, and Callisto).  As such, it gets pushed and pulled around pretty hard. Between Jupiter’s enormous gravity and the combined gravitational forces of the other three Galilean moons, it’s enough pushing and pulling to make anyone queasy.  And Io is a notoriously queasy planetoid.

Due to tidal forces, Io’s sulfur-rich interior is constantly boiling and churning.  And Io keeps literally spewing out its guts, making it the most volcanically active object in the whole Solar System.

Like Venus, my favorite planet, Io is a great chemistry professor, especially when it comes to sulfur chemistry.  Io’s also a pretty decent physics professor.  While most of the sulfur from Io’s volcanic eruptions settles back onto the moon’s surface, plenty of it escapes into space. The result: crazy dangerous games of particle physics in the vicinity of Jupiter.

Io’s ionized sulfur has a lot to do with controlling the intense radio emissions coming from Jupiter.  It’s also a major factor contributing to Jupiter’s insanely dangerous (to both humans and our technology) radiation environment. We recently learned that Jupiter has a third magnetic pole, located near the planet’s equator; while I haven’t read anything yet to back me up on this, I have a feeling Io is somehow responsible for that.

And lastly, Io’s ionized sulfur is partially (mainly?) responsible for the magnificent auroras that have been observed on Jupiter. And that’s my favorite bit about my favorite moon.  I love the idea that Io—the ugliest ugly duckling in the Solar System—plays such a crucial role in creating something beautiful.

But of course picking a favorite anything is a purely subjective thing.  Do you have a favorite moon?  If so, what is it?  Please share in the comments below!

Which Planet Has the Weirdest Magnetic Field?

When I did my yearlong Mission to the Solar System series back in 2015, the planet Neptune stood out as having the weirdest and wackiest magnetic field.  Here’s a totally legit photograph from 1989 taken by the Voyager 2 space probe.  As you can see, Neptune is really confused about how magnetic fields are supposed to work.

But since 2015, science has learned more about the other three gas giants in our Solar System.  Neptune’s magnetic field is still really weird, but it’s no longer clear that it is the definitive weirdest.

  • Jupiter: Based on data from the Juno mission, it looks like Jupiter has three poles instead of two.  There’s a north pole, right about where you’d expect it to be.  Then the magnetic field lines emanating from the north pole connect to two separate south poles.  The first south pole is about where you’d expect a south pole to be. The other one is near the equator. Click here for more about Jupiter’s “non-dipolar” magnetic field.
  • Saturn: As Sherlock Holmes says in one of his many adventures, “Depend upon it, there is nothing so unnatural as the commonplace.” According to data collected during the Cassini mission’s Grand Finale, Saturn’s magnetic field is almost perfectly aligned with its rotation.  At first blush, that might seem quite normal.  Commonplace, even. Except no other planet’s magnetic field is so perfectly aligned.  Not even close.  Apparently planetary scientists didn’t think such a thing was even possible.  Click here for more about the “negligible tilt” of Saturn’s magnetic field.
  • Uranus: The planet Uranus is tipped over sideways, and its magnetic field is tipped over further still.  According to recent computer simulations, these two factors combine to cause Uranus’s magnetic field to tumble over itself “like a child cartwheeling down a hill,” as one researcher put it. This leads to a “periodic open-close-open-close scenario” where the solar wind can flow in toward the planet then suddenly be blocked, then suddenly flow in again, and then suddenly be blocked.  If these simulations are correct, the Uranian aurora may flick on and off like a light switch. Click here for more about the “topsy-turvy motion” of Uranus’s magnetic field.
  • Neptune: In 1989, Voyager 2 discovered that Neptune’s magnetic field is lopsided. The magnetic field doesn’t run through the planet’s core. Instead it runs through a seemingly random point about halfway between the core and the “surface” (by which I mean the topmost layer of the atmosphere).  Also, only one of the poles ends up being near the planet’s “surface.”  The other pole is buried somewhere deep in the planet’s interior.  For more about Neptune’s “badly behaved” magnetic field, click here.

If I had to choose, I’d probably still give Neptune the award for weirdest magnetic field.  But the competition is a lot tighter than it used to be.  Maybe the real lesson here is that gas giants in general have wild and crazy magnetic fields.

So if you had to pick, based on all this new info, which planet do you think deserves the award for the weirdest magnetic field?

P.S.: Also, the Cassini mission discovered there’s an electric current flowing between Saturn and its innermost ring.