I’m always comparing astronomy to art, and sometimes that’s literally true, like when artist David Fuhrer creates amazing near-3D images of the planets:

That’s very cool, and even niftier, they’re to scale! The colors aren’t real — the image of Venus (next to Earth) he used is from radar mapping of the planet from the Magellan spacecraft, and Mercury (second from left) is actually a relatively uniform grey — but this really gives you a sense of the innermost terrestrial planets (and one bonus Moon — ours, all the way on the left in that image).

I also really like his depiction of Saturn. It makes me wish this were a real objet d’art; I’d love one for my living room.

You should also check out this family portrait of all the planets together — man, Jupiter and Saturn are way bigger even than Uranus and Neptune!

These images were created for a TV documentary, and I’ve filed David’s name away if I ever need it for something like this. He has other cool images, too. Digital imagery is really amazing, and I wonder how many people have been introduced to art — both the creation and appreciation of it — due to its advent?

Images used by permission of David Fuhrer. Tip o’ the electron to srahhh on Twitter.

Alex Parker is an astronomy PhD student at the University of Victoria, and had a neat idea: create music based on 241 supernovae found in a three-year-long survey of the sky. The data were from the Canada-France-Hawaii-Telescope, and he made a video of the effort:

Each note represents one of the supernovae. The volume is based on the star’s distance, and the pitch based on how long it took the supernova to rise to maximum brightness and fade away — that’s tied to the exploding star’s total energy released, and was the key factor used to discover dark energy — together, they are combined into this "Supernova Sonata". Clever, and cool.

Speaking of which, I also got an email from Mike Lemmon of Neue Music. For a website called Experience the Planets, he created music I’d characterize as "atmospheric" — more tonal and ethereal than most synth music. I happen to like this kind of stuff, and I find myself listening to his "Planets" as I’m working. It’s not for everybody, I know, but if you like that kind of thing as I do you should give it a shot.

It’s available on iTunes, or you can go to the link above and listen while thumbing through some incredibly beautiful artwork of the planets.

[UPDATE: The article discussed below is now online at Discover Magazine's website, so you can read it there.]

Every now and again I delve back into the ancient art of writing for an actual magazine that has words printed in ink on paper which gets sent to you via the postal service.

Quaint, I know.

But I wrote just such an article for Discover Magazine which is in the December 2010 issue. The article, called "Why Size Matters" is about why defining the word planet is proving to be so difficult.

Funny how writing works sometimes. I got the idea for the article while researching a blog post on a moon in the outer solar system. Curious about its size, I started poking around the web looking for other moon diameters, and then started wondering how big an object you need before gravity crushes it into a ball. I thought I could write the article about just that, but the words apparently had a mind of their own and went in a different direction. I wound up talking about what we think of as planets, and then in the middle of all this I read an advance copy of Mike Brown’s wonderful book How I Killed Pluto and Why It Had It Coming (full review coming soon). Mike spends quite a bit of time on this very topic, as you might imagine (he discovered the Kuiper Belt object Eris, which kick-started the demotion of Pluto). I found his thinking to be very similar to mine, and his writing actually gelled a lot of disorganized thoughts I had about all this.

Anyway, the article was fun to write, and I think anyone who likes my blog will like it. I got the issue in the mail the other day, and it’s on newsstands and at bookstores now. I hope you’ll check it out.

A science joke:

A woman is out walking and sees a kid on his hands and knees looking at the sidewalk. She asks the boy what he’s doing, and he says, "Looking for a quarter I lost." She asks him where he lost it, and he points across the street. Quizzically, she asks, "Then why are you looking here?" He replies, "The light’s better over here."

What’s this got to do with astronomy? I’m glad I asked.

Astronomers took a sample of 500 stars, 70 of which are known to have planets orbiting them, while the rest have no planets detected. They examined the spectra of the stars, looking specifically to see how much lithium was present. What they found, with good statistical significance, is that stars with planets had far less lithium than stars that did not have planets.

Somehow, having planets means a star loses its lithium. How the heck does that happen?

A brief digression. Lithium is a weird element. It’s the third lightest after hydrogen and helium, and unlike every other element after it on the periodic table, we don’t think it’s made inside stars. It’s too fragile; the nuclei get smashed up easily, and so it doesn’t last long in the cores of stars. That means that as far as we can tell, all the lithium in the Universe was created in the Big Bang.

Just because it gets wrecked in the cores of stars does not mean they have no lithium at all. Lithium created in the Big Bang would have been in clouds where stars formed, and if a lithium nucleus can avoid the core of the star by staying nearer the surface, it can survive. The Sun has lithium in it, for example, but at far less abundance (<1%) than what you see out in gas clouds. That means the Sun has destroyed a lot - but not all - of its lithium supply.

When astronomers look at other stars like the Sun, the amount of lithium they possess varies wildly. But now it appears that the amount of lithium in a Sun-like star depends on whether it has planets or not. Stars without planets have, on average, 10 times the lithium as stars with planets in the sample.

Weird.

It's possible to think of simple ways that a planet could affect the lithium abundance of a star. Maybe the gravitational tugging of the planet helps mix up the star's interior, letting the lithium get close enough to the core to get destroyed. Shortly after the star and planets form, the planets can migrate slowly toward the star over long periods of time, which might affect how rapidly the star rotates. That in turn will affect how deeply the star's outer convection layer can penetrate the interior (bringing lithium down with it, destroying the element; in fact, this is one scenario proposed by the team that made this discovery.

Or maybe it’s something else. Or maybe there is a third thing we haven’t thought of yet, something that both destroys lithium and allows the star to make planets. The presence of planets and depletion of lithium might be related, but not directly.

It’s a mystery, but astronomers love mysteries. More observations will no doubt uncover more clues, give us more data we can analyze to uncover yet more correlations.

And that brings me back to my joke at the start. The press release for this news story makes an interesting statement:

This finding does not only shed light on the lack of lithium in our star, but also provides astronomers with a very efficient way of finding stars with planetary systems.

I disagree with the philosophy of this conclusion. Sure, if you want to find stars with planets, it might make sense to concentrate on stars with depleted lithium abundance. But I think that’s not a great idea: you’re only looking where the light’s good. When planets were first discovered around sun-like stars, we were all surprised to find them very close to their parent stars, orbiting in days, not years. The reason they’d been missed for so long is that no one had thought to look for them in orbits that small! We’d been looking where the light was good (literally) and not where the planets really were.

I’m not saying it’s wrong to only look to lithium-poor stars when seeking planets, but I am saying that if you’re a planet hunter, you might want to open your criteria a bit. This lithium finding is very interesting, and may well play out to be a hard-and-fast law, but I think it’s still a little early to rule anything out just yet.

As always, the Universe knows what it’s doing. It’s our task to figure out just what that is.

Image credit: ESO/L. Calçada