Sciency Words: Metallicity (An A to Z Challenge Post)

April 15, 2017

Today’s post is a special A to Z Challenge edition of Sciency Words, an ongoing series here on Planet Pailly where we take a look at some interesting science or science related term so we can all expand our scientific vocabularies together. In today’s post, M is for:


Astronomers. All the other scientists had a meeting, and they all agree: there’s something wrong with those astronomers. For some reason, astronomers do not understand what is or is not a metal.

According to astronomers, the only elements that aren’t metals are hydrogen and helium.

Now it does make sense for hydrogen and helium to be special in astronomers’ eyes. By mass, something like 75% of the observable universe is hydrogen. Helium makes up almost all of the remaining 25%. And the hundred-plus other elements on the periodic table? All combined, all that other stuff constitutes less than 1% of the observable universe.

So for astronomers, it’s convenient to have a word that lumps all this “other stuff” together. But why does that word have to be metal? I’ve never found a wholly satisfactory answer for this, but I do have a personal theory.

Turns out that in technical shorthand, the amount of “other stuff” in a star is represented as [Fe/H]. That’s the chemical symbols for iron (Fe) and hydrogen (H). In other words, the amount of “other stuff” is quantified as a ratio (sort of) of iron to hydrogen (the math is a little more complicated than a simple ratio, but I won’t to get into that here).

I’m guessing that out of all the non-hydrogen, non-helium atoms you might expect to find in a star, iron must be the easiest—or at least one of the easiest—to identify with a spectroscope, and thus iron serves as a convenient proxy for everything else.

The quantity represented by [Fe/H] is called metallicity. Everyone would agree that iron is a metal, so that makes sense. But since metallicity actually tells us more than just the iron content of a star—since it also gives us a sense of how much carbon and silicon and argon etc is in that star—suddenly the word metallicity is covering metals and non-metals alike, in a way that comes across as very odd to everyone who isn’t an astronomer.

Next time on Sciency Words: A to Z, an electron by any other name would still be negatively charged.

Sciency Words: Magnetar

March 17, 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:


Space has a lot of cool ways to kill you. This one’s especially nifty! Magnetars are neutron stars with intensely powerful magnetic fields. Like, absurdly powerful magnetic fields.

Fly your spaceship near a magentar, and that overpowered magnetic field will start pulling the electrons off your atoms. This will kill you. It’ll destroy your spaceship too. Without those electrons, chemical bonds don’t work. Your molecules will unravel, and you and your ship will just disintegrate.

Even from a distance, magnetars are a menace. In 2004, a strong burst of gamma radiation washed over Earth, compressing our planet’s magnetic field and partially ionizing our atmosphere. That gamma radiation came from a magnetar on the other side of the galaxy.

If a magnetar could do that to us from so far away, just think what it must have done to any alien civilizations that happened to live closer. I can’t help but imagine there’s a vast dead zone on the other side of the galaxy, with magnetar SGR 1806-20 right in the middle.

The good news is that magnetars don’t last long. Their magnetic fields decay rapidly, so these raging monsters turn into regular neutron stars within a few thousand years. Also, while their outbursts of gamma rays and X-rays can affect our planet, there aren’t any magnetars close enough to Earth to really threaten us.

Oh wait. Yes there are. Sort of.

Sciency Words: Frost Line

December 23, 2016

Welcome to a very special holiday edition of Sciency Words! Today’s science or science-related term is:


When a new star is forming, it’s typically surrounded by a swirling cloud of dust and gas called an accretion disk. Heat radiating from the baby star plus heat trapped in the disk itself vaporizes water and other volatile chemicals, which are then swept off into space by the solar wind.

But as you move farther away from the star, the temperature of the accretion disk tends to drop. Eventually, you reach a point where it’s cold enough for water to remain in its solid ice form. This is known as the frost line (or snow line, or ice line, or frost boundary).

Of course not all volatiles freeze or vaporize at the same temperature. When necessary, science writers will specify which frost line (or lines) they’re talking about. For example, a distinction might be made between the water frost line versus the nitrogen frost line versus the methane frost line, etc. But in general, if you see the term frost line by itself without any specifiers, I think you can safely assume it’s the water frost line.

Even though our Sun’s accretion disk is long gone, the frost line still loosely marks the boundary between the warmth of the inner Solar System and the coldness of the outer Solar System. The line is smack-dab in the middle of the asteroid belt, and it’s been observed that main belt asteroids tend to be rockier or icier depending on which side of the line they’re on.

It was easier for giant planets like Jupiter and Saturn to form beyond the frost line, since they had so much more solid matter to work with. And icy objects like Europa, Titan, and Pluto—places so cold that water is basically a kind of rock—only exist as they do because they formed beyond the frost line. This has led to the old saying:


Okay, maybe that’s not an old saying, but I really wanted this to be a holiday-themed post.

Sciency Words: Flare Star

August 26, 2016

Sciency Words BIO copy

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 all expand our scientific vocabularies together. Today’s term is:


Good Star Trek fans will remember the Battle of Wolf 359, when the Borg came to assimilate us all. Thirty-nine Federation starships were lost. Nearly 11,000 people were killed. #NeverForget

Good Trekkies may also be aware of the fact that Wolf 359 is a real place. It’s a red dwarf star in the constellation Leo, located within a mere eight light-years from Earth.

Also, Wolf 359 is a UV Ceti variable star, or what is more commonly called a flare star. Flare stars experience dramatic, unpredictable increases in brightness across the EM spectrum, including increases in highly destructive X-ray and gamma ray emissions.

And when a flare star starts to flare up, it can happen quickly. In 1952, the star UV Ceti (for which the UV Ceti variable star category is named) became about 75 times brighter in a period of only twenty seconds.

It’s believed that the flare activity of flare stars is similar to the kind of solar flares we’ve observed on our own Sun. Except the Sun’s solar flares are usually not so intense. And when it comes those X-rays and gamma rays, our Sun doesn’t even come close to what spews out of flare stars.

So perhaps parking thirty-nine starships next to a flare star wasn’t the smartest thing Starfleet could have done. Maybe… just maybe… what happened at Wolf 359 wasn’t the Borg Collective’s fault.

Ag26 Battle of Wolf 359

P.S.: Another flare star has been in the news a lot lately: Proxima Centauri. We now know, thanks to the European Southern Observatory, that Proxima does have an Earth-like planet in orbit. So the next question is just how thoroughly that planet has been cooked by Proxima’s violent flare-ups.