Haumea Has Rings

October 18, 2017

I have to begin this post by apologizing to Pluto. Pluto, I’m sorry. You’re really neat and interesting and I like you a lot; but the truth is Haumea is now my favorite dwarf planet.

Last week, a paper in the journal Nature announced that the dwarf planet Haumea has rings.

Haumea’s rings were discovered during an occultation, when Haumea (as viewed from Earth) passed directly in front of a distant star. The rings caused the star to flicker slightly just before and after the occultation occurred. This, by the way, is exactly the same way the rings of Uranus were discovered.

Haumea was already a pretty strange and interesting object even before we knew about the rings. All planets (and dwarf planets too) bulge a little at the equator; that’s just what happens when you’re constantly spinning on one axis. But Haumea is spinning considerable faster than normal, completing a full rotation every 3.9 hours.

As a result, Haumea doesn’t just bulge at the equator; it’s stretched and elongated into an oval shape. But this brings us to some bad news. According to that same paper from Nature, Haumea’s shape is “inconsistent with a homogeneous body in hydrostatic equilibrium.”

The math went a little over my head on this one, but being in a state of hydrostatic equilibrium means an object is spherical, or at least ellipsoidal, due to the pull of its own gravity. This is one of the requirements for being a dwarf planet, according to the I.A.U.’s current definition.

So Haumea—which I just declared to be my favorite dwarf planet—might not be a dwarf planet at all! This could be good news for Pluto. If the I.A.U. decides to officially demote Haumea from dwarf planet to… I don’t know what, I guess Pluto will become my favorite dwarf planet again by default.


Molecular Monday: Boron Isn’t Boring

October 2, 2017

Welcome back to another edition of Molecular Mondays, a special biweekly series here on Planet Pailly combining two of my least favorite things: chemistry and Mondays.

At some point long, long ago, I read a book about the periodic table of the elements. Chapter five was about boron, and what I remember learning was that boron is kind of useless. Certain boron-containing compounds are used in cleaning detergents, and while boron is not particularly toxic to humans, it’s deadly to insects, so it makes a good insecticide.

And that was basically it. Nothing more to know. Time to move on to chapter six: carbon.

So when the news came out that the Curiosity rover had detected boron on the surface of Mars, my initial reaction was “who cares?” But then I read more, and I soon realized that I’d been grossly under-informed about the fifth element from the periodic table.

First off, finding boron on Mars posed a real challenge. The Curiosity rover used an instrument called ChemCam, which basically zaps rock samples with a laser and performs a spectroscopic analysis on the resulting rock vapor.

According to this paper published in Geophysical Research Letters, scientists were looking for two spectral lines, both in the ultraviolet part of the spectrum, which are characteristic of boron: 249.75 nm and 249.84 nm. Annoyingly, iron also produces a spectral line at 249.96 nm, so ChemCam can only confirm boron’s presence in samples that have low iron content, which are hard to come by on Mars. Iron oxide is basically everywhere.

But despite this difficulty, boron was detected. Why should I or anyone else care? Because it was detected in veins of sedimentary rock, meaning that at some point long ago when Mars still had lakes and rivers and oceans of liquid water, boron must have been mixed into that water (likely in the form of borate, a compound of boron and oxygen).

Again, why should anyone care? Because some of the fragile molecules necessary for life decompose in open water, but borate can help stabilize those molecules, allowing them to combine to form RNA. Boron itself is not incorporated into our modern DNA, but its presence here on Earth may have helped life get started—and if boron was present on Mars, mixed into ancient Martian waters, it could have helped life get started there too.

Could have. We still don’t know for sure, but as I’ve hinted previously I am planning a little trip to Mars aboard my imaginary spaceship. Stay tuned. I’ll be sure to let you know if I find anything.


Sciency Words: Moon

September 29, 2017

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:

MOON

There are three things I want to cover with today’s post. Firstly, for anyone who may not already know, Earth’s moon is officially called the Moon (with a capital M). Unless you don’t speak English, in which case it’s called whatever it’s called in your language, provided that you treat the word as a proper noun. This according to the International Astronomy Union (I.A.U.), the one and only organization with the authority to name and classify astronomical objects.

Phases of the Moon.

Of course the Moon is not the only moon out there, so I also want to talk a little about the official I.A.U. sanctioned definition of the word moon. Unfortunately there isn’t one, which seems odd given how the I.A.U. are such stickers about their official definition of the word planet.

A common unofficial definition is that a moon is any naturally occurring object orbiting a planet, dwarf planet, or other kind of minor planet (such as an asteroid or comet). Except this definition creates some problems:

Saturn has like a bazillion moons!

Since there’s no lower limit on size or mass, you could consider each and every fleck of ice in Saturn’s rings to be a moon.

The Moon isn’t a moon!

In a very technical sense, the Moon does not orbit the Earth. The Earth and Moon both orbit their combined center of mass, a point called a barycenter. In the case of the Earth-Moon system, the barycenter happens to lie deep inside the Earth, so this distinction may not seem important, but…

Pluto is Charon’s moon, and Charon is Pluto’s!

The barycenter of the Pluto-Charon system is a point in empty space between the two objects. Pluto is the larger of the pair, so we generally consider Charon to be Pluto’s moon; however, you could argue that Pluto and Charon are moons of each other. You could even write a love song about their relationship.

Of course I’m not seriously arguing that Saturn has billions upon billions of moons, nor am I arguing that our own Moon is not really a moon. There does seem to be some ambiguity about Charon’s status (is Charon a moon, or are Pluto and Charon binary dwarf planets?), but I’m not sure if this ambiguity has caused any real confusion in scientific discourse.

Still, as we learn more about moons in our own Solar System and also moons in other star systems, I think the I.A.U. will eventually have to come up with an official definition. And that brings me to the third and final thing I wanted to cover today: exomoons.

An exomoon would be defined as a moon (whatever that is) orbiting a planet or other planetary body outside our Solar System. Finding exoplanets is hard enough, so as you can imagine, searching for exomoons really stretches the limits of current telescope technology. But astronomers are trying, and next month (October, 2017) the Hubble Space Telescope will be making special observations of a planet named Kepler-1625b in an attempt to confirm a possible exomoon detection.


Exoplanet Explorer: WASP 12b

September 28, 2017

Imagine you’re a poor, helpless planet orbiting a normal yellow dwarf star, a star not so dissimilar to our own Sun. But that star keeps drawing you closer and closer… and closer. You know this could end badly for you, but you cannot resist. Soon, it’s too late. Like the monster from Stephen King’s It, the star is going to eat you alive.

Such is the fate of WASP 12b, an exoplanet discovered in 2008 by the SuperWASP planetary transit survey. Wasp 12b is a carbon rich planet, with an atmosphere of mostly methane and carbon monoxide, and astronomers suspect the planet’s core might be made of graphite and diamond.

You could describe WASP 12b as a hot Jupiter, a gas giant that’s strayed perilously close to its parent star. WASP 12b is also sometimes referred to as a chthonian planet, though in my opinion that seems a bit premature. The planet appears to be in its final death throes, so to speak, but it’s not quite dead yet.

In 2010, observations by the Hubble Space Telescope revealed that the planet’s atmosphere is being stripped away, with streams of matter falling toward the star to be “consumed.” Eventually all that will remain of WASP 12b is its core. At that point, I think the term chthonian planet will be appropriate.

That is assuming, of course, that anything will remain at all. Given how violently WASP 12b is being destroyed, it’s possible even that diamond core will be ripped apart and devoured. According to current estimates, we’ll have to wait about 10 million years to find out—a surprisingly short period of time in the cosmic scheme of things.

P.S.: To my surprise, WASP 12b has started making headlines just in the last few days. Astronomers recently determined the planet is incredibly dark in color, almost pitch black. That seemed strange to me at first, but I guess if you’re going to have a planet with that much carbon, the dark coloration kind of makes sense.


Exoplanet Explorer: COROT 7b

September 26, 2017

In 2009, the French-built COROT space telescope made an astonishing discovery: a planet. A planet that was, at least at the time, the most Earth-like exoplanet ever discovered. Except as we’ve discussed previously, “Earth-like” exoplanets are not necessarily much like Earth. In this case, the term chthonian planet may be a better fit.

Exoplanets are often named after the telescope used to discover them; therefore, this planet has been officially designated COROT 7b (the T, by the way, is silent… it’s a French thing). A press release announcing COROT 7b’s discovery said it has a surface you can walk on. That’s true enough, but I don’t recommend going for a stroll there. The weather forecast sounds terrible.

It’s believed that COROT 7b started out as a gas giant, like Jupiter or Saturn, but it was drawn into an orbit way too close to its parent star. Due to the star’s intense heat and radiation, COROT 7b’s entire atmosphere would have boiled away, leaving only the shrunken, shriveled core of the planet behind.

That shrunken core, which is still orbiting way too close to its parent star, is predicted to be tidally locked, meaning one side of the planet is always facing the sun and the other side is always turned away. That creates an enormous temperature discrepancy similar to, but more extreme than, the temperature discrepancy on Mercury.

And according to this paper from the Royal Astronomy Society, the temperature on the daylight side is high enough to vaporize rock. Allow me to emphasize that point. It’s not just hot enough to melt rock; oh no, that would be too normal. It’s hot enough to vaporize rock. So while COROT 7b seems to have lost its original atmosphere, it may have developed a new atmosphere composed of gaseous sodium and silicon and iron, along with other things we’re not accustomed to thinking of as atmospheric gases.

Then on the night side, where the temperature is much colder, all that vaporized rock would condense to form “mineral clouds,” and pebbles would fall like rain. Or perhaps hail is a more apt analogy. Anyway, if you’re going to go for a walk on COROT 7b, you’ll need more than an umbrella to deal with the weather.


Sciency Words: Chthonian Planet

September 22, 2017

Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us expand our scientific vocabularies together. Today’s term is:

CHTHONIAN PLANET

In ancient Greece, there were two ways to pray: with your arms raised up to the gods of Olympus or with your arms lowered in deference to the gods of the underworld, also known as the chthonic or chthonian deities.

Regarding spelling and pronunciation, the “chth” thing makes more sense if you’re familiar with how the Greek alphabet works. Much like the “p” in psychology or the “h” in rhinoceros, the “ch” in chthonian becomes silent in English.

English often retains these silent letters as a way to remind us of a word’s origin and history. Also, we have to do something to keep our spelling bees interesting.

Chthonian became an astronomy term in 2003 thanks to this paper: “Evaporation rate of hot Jupiters and formation of Chthonian planets.” The paper describes a scenario in which a hot Jupiter—a gas giant orbiting waaaaay to close to its parent star—has its entire atmosphere stripped away by solar radiation. Only the planet’s rocky and/or metallic core remains. It would probably look something like this:

This is actually a pretty clever play on the original meaning of chthonian, which could refer to the underworld and all things death-related OR could just mean the earth and everything beneath its surface.

In one sense, chthonian planets are dead. Very, very dead. Also, because a chthonian planet is still located dangerously near to its parent star, conditions there would be truly hellish. But in another sense, these chthonian planets would look like any other Earth-like exoplanets, meaning they are rocky, terrestrial worlds, as opposed to Jupiter or Saturn-like gas giants.

For the time being, the idea of chthonian planets is still more or less theoretical. We have not yet proven definitively that such worlds exist. However, several candidate chthonian planets have been identified. I’ll introduce you to two of them next week.


In Memory of Cassini

September 20, 2017

Last week, NASA’s Cassini Mission came to an end when the spacecraft crashed into the planet Saturn. This was, of course, a planned event: a way for the mission to end in a blaze of glory, collect a little extra data about Saturn’s atmosphere, and also protect Saturn’s potentially habitable moons (Titan, Enceladus, and possibly also Dione) from microorganisms that may have hitched a ride from Earth aboard the spacecraft.

Cassini’s last few days were an oddly emotional time, at least for me. Somehow knowing that the end was coming, that everything was proceeding according to schedule, made it a little harder to bear. When the words “data downlink ended” started appearing in my Twitter feed, I got a little misty eyes and had to walk away from the computer for a while.

This despite the fact that I never got to know Cassini all that well. I never really followed the Cassini Mission closely (especially compared the way I follow Juno). Looking back through my old posts, it seems Cassini only ever appeared on this blog twice. Once for that time it spotted sunlight glinting off the surface of Titan’s methane lakes…

… and once more for the time it used precise measurements of Enceladus’s librations to determine that Enceladus does indeed have an ocean of water beneath its crust.

So today I thought I’d turn the floor over to several of the moons of Saturn and also Saturn herself. They’re the ones who got to know Cassini well. Not me. It’s right that they get the chance to give Cassini’s eulogy.