Sciency Words: Spectroscopy

September 2, 2017

Welcome to a special Saturday edition of Sciency Words, because sometimes life gets in the way of regular blogging schedules. Each week (normally on Fridays) we take a closer look at some science or science-related term so we can all expand our scientific vocabularies together! Today’s term is:

SPECTROSCOPY

What color is it? It sounds almost like a childish question, but as we look out into space, trying to study the Sun and other stars and distant planets, we can learn a great deal just by figuring out what color things are.

The science of spectroscopy has a long history, beginning with Isaac Newton. In the late 1600’s, Newton demonstrated that pure white light can be split apart into a rainbow of color using a prism. Newton called this a spectrum, from the Latin verb specto, meaning “I observe” or “I see.” (According to my trusty Latin-English dictionary, the noun spectrum also meant “apparition” or “ghost.”)

Over the decades and centuries to come (click here for a detailed timeline), scientists used increasingly sophisticated combinations of lenses, mirrors, and prisms to study Newton’s spectrum in greater detail. They also experimented on a wide variety of light sources: sunlight, starlight, firelight, and even electrical sparks.

An especially noteworthy experiment in 1752 showed that burning a mixture of alcohol and sea salt produced an unusually bright yellow band in the middle of the spectrum (we now know this to be a emission line for sodium). And in 1802, another experiment on sunlight revealed multiple dark bands in the Sun’s spectrum (which we now know are absorption lines for hydrogen, helium, and other elements in the Sun’s photosphere and corona).

All the colors of the rainbow, except a few are missing. This is an absorption spectrum.

It wouldn’t be until the early 20th Century, with the development of quantum theory and, specifically, Niels Bohr’s model of the atom, that anyone could explain what caused all these spectral lines.

No rainbow, just a few specific colors. This is an emission spectrum.

In Bohr’s atom, the electrons orbiting an atomic nucleus can only occupy very specific energy levels. When electrons jump from one energy level to another (the true meaning of a quantum leap), they either emit or absorb very specific frequencies of light. The light frequencies are so specific that they act as a sort of atomic fingerprint.

And so today, as we look out into the universe, seeing the glow of stars and the absorption patterns of planetary atmospheres, it’s possible for us to identify the specific chemical elements we’re seeing, even across the vast distances of space, simply by asking what color is it?


One Last Thing About the Eclipse

August 30, 2017

This hasn’t been much of a research week for me. I’m more focused on the fiction side of my writing at the moment, rather than the science stuff.

So today I’m just sharing some artwork, something I didn’t quite get done in time for the eclipse.

You know, we are kind of lucky that we have these total solar eclipses. By some amazing coincidence, our large Sun and small Moon appear to be the same size in Earth’s sky, allowing the Moon to perfectly cover up the Sun.

That doesn’t happen anywhere else in the Solar System. That perfect planet-moon-star alignment is likely rare, perhaps even unique in our galaxy. So whenever we make first contact with aliens, and they start bragging about their luminous forests or crystal waterfalls or whatever, we Earthlings will have a unique and beautiful thing to brag about to: we have total solar eclipses.


Eclipse Day 2017 and Hermione Granger

August 23, 2017

One of my favorite fictional characters—one of the characters I most strongly identify with—is Hermione Granger from the Harry Potter series. She’s depicted as extremely bookish, and at one point we’re told she’s nervous about flying because it’s “something you couldn’t learn by heart out of a book.”

Yup, that sounds like me. I’ve spent an enormous amount of time studying science, but almost everything I know comes out of books rather than from hands on experience.

And so as the Great American Eclipse of 2017 approached, I felt increasingly nervous, just like Hermione going out for her first flying lesson. I’d read a lot about the eclipse, done pretty thorough research about the kinds of glasses I’d need to buy, and yet… I still felt horribly unprepared.

To make matters worse, the eclipse glasses I’d ordered online seem to have gotten lost in the mail. On the day of the eclipse, they still hadn’t arrived. I had a backup plan, but I wasn’t sure if it was going to work. I’d read online that you can use a pair of binoculars to project an image of the Sun onto a piece of paper. Again, I’d read about this, but I’d never tried to do it, and I wasn’t 100% convinced this was going to work for me. Some of the instructions I’d read sounded kind of complicated.

And yet to me extraordinary delight, it worked! My hands were a bit shaky, but I was able to project the Sun onto a page of my sketchbook and watch as the Moon slowly moved across the image.

My hastily improvised eclipse observatory.

Watching the eclipse turned out to be a highly emotional experience for me. I’ve been going through some things in my personal life, and this was a powerful reminder that no matter what happens, the universe keeps turning. Also, I realized at one point that the binoculars I was using originally belonged to my Dad, so in a sense it was like I got to share the experience with him.

And lastly, for a Hermione Granger-type person like me, this was one of those rare moments when something I read about became real to me. Maybe it wasn’t as exhilarating as learning to fly on a broomstick, but still… Eclipse Day 2017 was a magical experience for me.


Sciency Words: Coronal Heating Problem

June 9, 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:

CORONAL HEATING PROBLEM

This is the Sun. He’s kind of a big deal, and he knows it.

The interior of the Sun is several million degrees Celsius. By comparison, the surface of the Sun is quite chilly. It’s only a few thousand degrees. Still, if you were standing on the surface of the Sun, you wouldn’t last long.

But before you launch yourself into space to escape the heat, there’s something you should know: as you fly away from the Sun, passing through the corona, the temperature starts getting hotter again. It’s not quite as hot as the interior, but still… we’re back into million-plus degree heat.

If that doesn’t make sense to you, that’s okay. It doesn’t make sense to me either, or anyone else. Astro-scientists have been baffled by this for decades now. They call it the coronal heating problem.

I first heard about the coronal heating problem back in 2014, when I was starting my research for what became the 2015 Mission to the Solar System. To be honest, it’s not something I’ve spent a lot of time thinking about since then. Every once in a while, it comes up again and I think, “Oh right… so they still haven’t figured that out yet?”

But as you may heave heard last week, NASA’s on the case. Their newly named Parker Solar Probe is going to skim very close to the Sun and try to figure out what the heck’s going on.

Parker is scheduled for a launch window in July/August of 2018. Its mission is expected to last until 2025. So hopefully a decade from now, whenever I’m reminded of the coronal heating problem, it won’t be a problem anymore, and I’ll be able to think, “Oh right… they finally figured that out!”


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:

FROST LINE

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:

dc23-outer-solar-system-christmas-party

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


Sciency Words: Apollos and Atens

November 25, 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 expand our scientific vocabularies together. Today we’ve got two terms:

APOLLOS and ATENS

Asteroid are classified into different “groups” based on their orbital properties. The Apollo asteroids and Aten asteroids are two such groups, and these groups are of particular interest to anyone who doesn’t want a repeat of the K-T Event (which wiped out the dinosaurs) or the Tunguska Event (which flattened a forest and could have done the same to a whole city).

Technical Definitions

  • Apollo asteroids have a semimajor axis greater than 1.0 AU and a perihelion less than Earth’s aphelion of 1.017 AU. The first known Apollo was 1862 Apollo, for which the group is named.
  • Aten asteroids have a semimajor axis less than 1.0 AU and an aphelion greater than Earth’s perihelion of 0.983 AU. The first known Aten was 2062 Aten, for which the group is named.

Less Technical Definition

  • Apollo asteroids spend most of their time beyond Earth’s orbit, but cross inside at some point.
  • Aten asteroids spend most of their time inside Earth’s orbit, but cross outside at some point.

nv25-apollo-and-aten-orbit-diagrams

The important thing to know is that both Apollos and Atens cross Earth’s orbit at some point. Keep in mind that space is three-dimensional, so their paths don’t necessarily intersect with Earth’s. They might pass “above” or “below” Earth, so to speak.

But the orbits of enough Apollos and Atens do intersect with Earth’s orbital path that they might one day hit us. Atens are particularly worrisome. They spend so much time inside Earth’s orbit, in relatively close proximity to the Sun, that it’s hard for astronomers to find them.

So if a giant asteroid ever does sneak up on us and wipe out human civilization, my guess is it’ll be an asteroid from the Aten group. Those are the asteroids that frighten me the most.

nv25-aten-asteroid


Sciency Words: Solar Wind

January 8, 2016

Sciency Words MATH

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 word is:

SOLAR WIND

The Sun produces more than just sunlight. In addition to boring, electrically neutral photons of various wavelengths, the Sun also unleashes a near constant onslaught of electrically charged particles that wreak havoc upon the Solar System.

These charged particles are collectively known as the solar wind, and they come in two groups: slow and fast. The slow solar wind originates mainly from the Sun’s equator and travels at a leisurely 400 kilometers per second. The fast solar wind moves at almost twice that speed. It comes from coronal holes (low density regions of the corona) which tend to form near the Sun’s poles.

Both types of solar wind exert a slight pressure on everything they touch, from planets and moons to comets and asteroids. This is a slight pressure, but over long stretches of time it’s enough to nudge asteroids off course, clear dust and debris from the inner Solar System, and strip away entire planetary atmospheres.

Luckily for us, Earth can protect itself. Remember: the solar wind is composed of electrically charged particles, and Earth has a global magnetic field. As a result, the solar wind cannot blast Earth directly. For the most part, the magnetic field either repels solar wind particles away or directs them toward Earth’s poles (where the particles trigger auroras).

That’s good news for us humans, but don’t relax yet. The solar wind varies in intensity, turning from a gentle breeze into explosive solar storms.

Ja03 Ejecta

Earth’s magnetic field still protects our planet during these storms, but not our technology. We learned this the hard way in 1859 when a huge coronal mass ejection struck Earth head on. It was too much, and Earth’s magnetic field sort of freaked out, overloading the global network of telegraph wires. If this happened again today, with our fancy Internet and power grids and satellites, it would… actually, no one really knows what would happen.

Also, the solar wind is a form of radiation, composed primarily of broken pieces of hydrogen and helium atoms. The crew of the International Space Station are still protected (somewhat) by Earth’s magnetic field, and the Apollo Missions to the Moon were brief enough to keep total radiation exposure for astronauts fairly low.

But the future of human space exploration, both in reality and in science fiction, very much depends on this question: how do we protect ourselves from the solar wind?