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.