Sciency Words | Planet Pailly

Sciency Words: Macromolecule

July 13, 2018

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:

MACROMOLECULE

After all the years I’ve been writing Sciency Words, I’ve noticed something. A lot of times it might seem pretty obvious what a scientific term means, but then you dig a little deeper and find that the term is not so clearly or precisely defined as you’d expect.

Defining macromolecule should be easy. Macro means big, molecule means molecule; ergo, a macromolecule is a big molecule. But after I read this paper about the discovery of organic macromolecules on Mars, I had a question: just how big does a molecule need to be to get that macro- prefix?

German chemist Herman Staudinger is credited with coining the term macromolecule. It was a highly controversial concept at the time. Another German chemist, Nobel laureate Heinrich Wieland, wrote to Staudinger in the 1920’s saying: “My dear colleague, drop the idea of large molecules; organic molecules with a molecular weight higher than 5000 do not exist.” But Staudinger would later become a Nobel laureate himself for proving that they do.

I take that Wieland quote to mean that the word macromolecule was defined as any molecule with a molecular weight in excess of 5000, but I’ve seen other sources claiming it was defined as any molecule containing one thousand or more atoms, and still other sources saying it’s ten thousand or more atoms.

But those were the kinds of definitions being used in the early 20th Century. Modern usage gets far more complicated and confusing. As Wikipedia explains, the definition of macromolecule “varies among the disciplines.”

In biology, there are four kinds of macromolecule: lipids, proteins, nucleic acids, and carbohydrates. If it’s not one of those four things, it’s not a macromolecule, according to a biologist.
Polymer scientists go by a definition set by the International Union of Pure and Applied Chemistry (IUPAC), which states that a macromolecule is a “molecule of high relative mass, the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass.”
Wikipedia also mentions a definition that involves aggregates of molecules sticking securely together due to intermolecular forces rather than covalent or ionic bonds.

It’s not unusual for one word to be defined in different ways by different fields (see my post on metallicity). This is a big reason why some scientific terms end up being so difficult to define.

As for those organic macromolecules Curiosity found on Mars… in the context of that research, I think macromolecule simply means “very big molecule.” Like I said on Wednesday, we don’t really know what, specifically, Curiosity found, and maybe we never will. We just know that it must’ve had a lot of very big molecules in it.

2 Comments | Sciency Words, Space, Mars | Permalink
Posted by J.S. Pailly

Sciency Words: Aromatic

July 6, 2018

AROMATIC

At some point when I was a little kid, I discovered that gasoline doesn’t smell terrible. In fact, it has an almost sweet aroma to it. I got in a lot of trouble for this because, for obvious reasons, my parents didn’t want me sniffing gas fumes. But still, that subtly sweet smell is there, and it’s caused by a chemical known as benzene.

Apparently I’m not the only person to take note of benzene’s smell. German chemist Augustus Wilhelm Hofmann is credited with the first usage of the word “aromatic” to describe benzene, along with a whole host of other sweet-smelling chemicals.

Hofmann seems to have realized not only that these chemicals smelled similar but also that they had similar chemical compositions. “Of this series,” Hofmann wrote in 1855, “few members are at present known, but the group of aromatic acids is itself very imperfect and limited.” In other words, Hofmann predicted the existence of more “aromatic” chemicals that should fit the pattern.

And more chemicals of this series were later discovered, and we now know what they really have in common: a flattened, ring-like chemical structure, as pictured below:

As an adult, I know better than to sniff gasoline, and as an artist I know better than to sniff my art supplies. But the xylene used as a solvent in some pens and markers does have that same vaguely sweet aroma as benzene. However, not all of the chemicals we call “aromatic” smell so nice, or smell at all. It’s the flattened, ring-like structure that defines aromaticity today. The odor is no longer considered relevant.

You might be wondering then why we still call these chemicals aromatic, if their aromas aren’t important. This seems to be another case of scientists naming something before they really understood it. The same thing happened with the word organic. The term was used so often in scientific literature and became so deeply ingrained in the scientific lexicon that we’re now unable to change it.

The ring-like structures in aromatic chemicals are incredibly strong and unlikely to break apart during chemical reactions. That makes them really good structural components for the large, complex molecules that make life possible here on Earth—and may have once made life possible on Mars. But we’ll talk more about that next week!

2 Comments | Chemistry, Mars, Sciency Words, Space | Permalink
Posted by J.S. Pailly

Sciency Words: Coatlicue

June 8, 2018

COATLICUE

You may recall the famous words of Carl Sagan: “We’re made of star stuff.” Turns out we’re not made of just any old star stuff. No, a great deal of our stuff came from one star in particular, a giant star named Coatlicue that went supernova about 4.5 billion years ago.

I first saw this name in a recent article from Scientific American called “The New Biography of the Sun,” which in turn referenced a paper from the journal Astronomy & Astrophysics titled “Solar System Genealogy Revealed by Extinct Short-Lived Radionuclides in Meteorites.”

In short, certain radioactive isotopes found in our Solar System can be thought of as our Solar System’s D.N.A. The authors of that “Solar System Geneaology” paper used some of those isotopes (most notably aluminum-26) to try to reconstruct our Sun’s family tree and give us some idea about what the Sun’s “mother” must have been like.

Coatlicue would have been a giant star, approximately 30 times as massive as our Sun, ensconced within a giant molecular cloud along with other giant star siblings. This is sort of like what we see today with the stars of the Trapezium inside the Orion Nebula.

About 4.5 billion years ago, Coatlicue went supernova. The explosion accomplished two things: it seeded the surrounding molecular clouds with heavy elements (like aluminum-26) and, because of the force of the explosion, caused those molecular clouds to compress, triggering new star formation.

I have to confess that I feel like there’s a lot of guesswork and speculation going on here about how, specifically, Coatlicue died and how, specifically, the Sun and its planets were born. But the general idea that the death of one star triggers the formation of others is consistent with what we already know about star formation, so it makes sense to me that something like this must have happened for our own Solar System.

As for the name Coatlicue (which I believe is pronounced Kwat-LEE-kway), that comes from Aztec mythology. Coatlicue was the mother of the Sun. So that makes sense. In the myth, Coatlicue was also the mother of the stars, which actually sort of matches up with the science too. That supernova explosion 4.5 billion years ago would have triggered the formation of other stars—perhaps several hundred of them—in addition to our own Sun.

I didn’t see this in either Scientific American or that “Solar System Genealogy” paper, but I’d like to believe Coatlicue might not have been totally destroyed in that supernova. Perhaps some remnant is still out there, living on as a neutron star or a black hole or something. If so, I doubt we’ll ever find it, but if I know anything about mothers, I’m sure our Sun still hears from Coatlicue every now and then.

4 Comments | Sciency Words, Space, Stars, Sun | Permalink
Posted by J.S. Pailly

Sciency Words: Thiea

June 1, 2018

THEIA

When I wrote about the Nice model, I said it does a nice job (pun intended!) of explaining how the planets of the Outer Solar System started out, and how they ended up where they are today. But what about the Inner Solar System? Well, it turns out we may have started with a few more planets than we have today, and one of those hypothetical early planets has been named Theia.

Technically speaking, Theia wouldn’t have been a planet (not according to the I.A.U. definition), but it was definitely planet-sized, perhaps as large as modern day Mars. But Theia had to share its orbit with another planet that wasn’t technically a planet (yet): Earth.

Theia got stuck near one of Earth’s Lagrange points, about 60 degrees ahead of Earth in Earth’s almost circular orbital path. There’s some weird gravitational voodoo going on at these Lagrange points, and so this arrangement of Earth and Theia could theortically have remained stable long term.

Except Jupiter and/or Venus disrupted the gravitational balance, pulling Theia a little this way, a little that way, nudging Theia away Earth’s Lagrange point and closer to Earth itself, until one day….

I would call this the worst disaster in Earth’s history, except this collision was sort of the moment when Earth (as we know it) really began. I gather there’s still a lot of disagreement about the details, like whether this was a head-on collision or more of a glancing blow, but the two really important things to know are:

Theia knocked a large amount of Earth debris into space. That debris eventually coalesced to form our Moon.
Most of Theia is probably still here.Theia has become part of Earth, and the bulk of Theia may have would up becoming Earth’s core.

This idea that early Earth suffered a cataclysmic collision with another planetary body has been credited to a lot of different people, but it first appeared in the scientific literature in this paper from 1975. The name Theia wasn’t introduced until much later, in this paper from 2000.

In Greek mythology, Theia was the Titaness who gave birth to the Moon. That checks out. The name definitely seems appropriate. In the myth, Theia also gave birth to the Sun. That part doesn’t match up with the science so well.

But not to worry! In next week’s episode of Sciency Words, we’ll meet the Sun’s real mother.

4 Comments | Earth, Moon, Sciency Words, Space, Theia | Permalink
Posted by J.S. Pailly

Sciency Words: Degeneracies

May 25, 2018

DEGENERACIES

Okay, I have to be honest with you: I really don’t understand what this term means. It’s a statistics thing, and it gets really mathy. But since I came across this term in a paper about the TRAPPIST-1 planets, I felt I should try to get some sense of what a degeneracy is. What I learned, at least in relation to planets, was interesting enough that I thought it was worth sharing with you.

Imagine we’re playing a game of “Guess Who?” You know my person has red hair, but you still don’t know my person’s age or gender, you don’t know if my person is wearing glasses, or if my person has freckles. That one datapoint—my person has red hair—eliminates a lot of possibilities from the board, but there are still plenty of possibilities left over.

Those left over possibilities can be refered to as degeneracies (if I’m understanding the proper usage of this term). In that paper on the TRAPPIST-1 planets, it says: “The derivation of a planetary composition from only its mass and radius is a notoriously difficult exercise because of the many degeneracies that exist.”

In other words, if you’re playing “Guess Who?” with planets, knowing a planet’s mass and volume (and thus being able to calculate its density) still leaves you with a whole lot you don’t know about that planet.

This reminds me a lot of the Earth Similarity Index and the problems with using that system to identify Earth-like planets. Venus, for example, scores rather highly on the E.S.I. because its mass and volume are so similar to Earth’s, but Venus is not at all Earth-like in the sense that most people mean when they talk about Earth-like planets.

I’d say I plan to study this concept more, but I think I’m done for now. I tried to read this paper from 2010 which seems to have introduced the subject of degeneracies to planetary science and warned that they’d be a real problem in the study of exoplanets. But after attempting to slog my way through that paper, I think I’ve had enough mathy stuff for a while.

2 Comments | Sciency Words, Space, TRAPPIST-1 | Permalink
Posted by J.S. Pailly

Sciency Words: Nice Model

May 18, 2018

NICE MODEL

I recently assembled Lego’s Saturn V rocket set, and I have to say it’s a really nice model. It even has these little orange pieces to represent the floaty things for when the Apollo capsule returns to Earth and splashes down in the ocean. That, I thought, was a really nice touch!

But as nice as that Lego model is, that’s not the model we’re talking about today. Nope, today we’re talking about the Nice model, with a capital N.

In May of 2005, three papers were published in the journal Nature which did a nice job explaining some of the big mysteries of our Solar System.

First (in order of page number) was a paper on the anomalous orbital eccentricities and inclinations of the four gas giant planets.
Next came a paper on the Trojan asteroids which hang out around Jupiter’s Lagrange points, 60º ahead and 60º behind Jupiter in its orbital path.
And lastly, there was a paper on the Late Heavy Bombardment, a period of time when the Moon (and also the four inner planets) got pummeled with asteroids.

All three of these papers share a common idea: that the four gas giants of our Solar System must have started out much closer together, with a broad disk of rocky and icy debris beyond them, like a super-sized Kuiper belt. Then, approximately 700 million years after their initial formation, three of those gas giants (Saturn, Uranus, and Neptune) started drifting farther and farther away from the Sun and away from each other.

Jupiter seems to have drifted slightly closer to the Sun, but stopped short of entering and demolishing the inner Solar System thanks to a last minute gravitational interaction with Saturn (thanks, Saturn!).

As the gas giants spread out, they threw that super Kuiper belt into chaos. Some of that rocky and icy debris was hurled toward the inner planets, causing the Late Heavy Bombardment. Some of the debris got stuck around Jupiter’s Lagrange points, becoming the Trojan asteroids. And with so many complicated gravitational interactions happening at once, it’s no wonder the four gas giants ended up with some anomalies in their orbital paths.

This one idea—that the gas giants drifted apart after they formed—does a pretty nice job explaining three of the biggest mysteries about our Solar System. But sadly, that’s not why it’s called the Nice model. The name actually isn’t pronounced like the English word “nice” but rather like the French city of Nice (which rhymes with geese or fleece). That’s because the model was originally formulated at an observatory in Nice, France.

Unfortunately, I didn’t find that out until I’d already sprinkled a bunch of nice puns into this post, and I don’t feel like taking them out.

5 Comments | Jupiter, Neptune, Saturn, Sciency Words, Space, Uranus | Permalink
Posted by J.S. Pailly

Sciency Words: Voorwerp

May 11, 2018

VOORWERP

In 2007, Dutch schoolteacher and citizen scientist Hanny van Arkel was participating in the Galaxy Zoo project. She was sorting through photos of galaxies (there are so many galaxies out there, scientists need help sorting through them all) when she came upon the image of a weird, green, blob-like object.

This mysterious object came to be known as Hanny’s Voorwerp, because voorwerp is the Dutch word for object.

Image courtesy of Wikipedia.

It’s hypothesized that the spiral galaxy in the upper part of the image had a quasar flare up at some point. The resulting super accelerated jets of radiation must have hit a giant dust cloud, which we now see glowing green.

The quasar has since stopped, or at least calmed down for now, but that distinctive green glow can persist for tens of thousands of years. The color is almost certainly caused by ionized oxygen atoms.

Hanny’s Voorwerp is enormous, roughly the same size as our own Milky Way Galaxy. We now know of several other glowing green blobs hanging around other suspected former quasers. This paper identifies nineteen of them, and this collage from Wikipedia shows eight.

Image courtesy of Wikipedia.

These are commonly known as voorwerpjes. I have to admit I don’t know anything about Dutch (my linguistic education focused on Latin and Greek), but according to Wiktionary.org the j-part creates a diminutive form. So Hanny’s Voorwerp is the big “object” and the others are like cute, little “objectlings.” Well, little on the astronomical scale, at least.

Future research on Hanny’s Voorwerp and those voorwerpjes may tell us more about how quasar activity fluctuates over time. Also, it seems that getting zapped by a quasar may have triggered star formation inside Hanny’s Voorwerp. So we may be witnessing the very, very earliest beginnings of a brand new galaxy.

5 Comments | Hanny's Voorwerp, Sciency Words, Space | Permalink
Posted by J.S. Pailly

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