Recently, I was performing the mundane task of taking out the trash.

I went from room to room, collecting the detritus of the week. I then spent a few minutes scooping out and changing the cat litter, and, sighing, finally tied up the bag and hauled it out to the bins around the side of the house.

As I lugged the hefty bin out to the curb in the darkness, I did what I do, what I always do, when I go outside: I looked up.

I was greeted instantly with an astonishing sight: the reddish, glowing dot of Mars bumped right up against Regulus, the brightest star in Leo. The two were paired less than a degree between each other, low over the western horizon.

It was beautiful. Mars was the slightly brighter of the pair, and even in the mildly light-polluted and sparsely clouded night sky of Boulder I could see the color difference between the planet, some 240 million kilometers away, and the star, 3 million times farther distant yet.

I let my gaze drift a bit over and saw Saturn looming near Leo’s other end. Venus, I knew, was already behind the mountains, but I could see the Big Dipper standing on its bowl to the northwest. Following the arc of the dipper’s handle, I was led to mighty Arcturus, an orange giant nearing the end of its life, and a harbinger of things to come for our own star. Turning, was that Vega I saw dancing in between my neighbor’s tree branches? Why yes, yes it was. Summer’s coming, Vega is telling me.

My trash-hauling chore was forgotten. I suddenly had a flashback, visceral and total, of being a teenager. Standing at the end of my family’s driveway, I watched the sky. Every clear night you’d find me out there. I spent hundreds of hours, thousands, either gazing with my eye to the telescope or simply with my chin tipped up, the Universe unfolded above me. I would always have to pause when a car drove by, and while my absorption with the task didn’t allow it to occur to me then, I now wonder how many of those people saw me and thought to themselves that I was wasting my time.

But as I stand outside my house as an adult, gaping up at the sky, I am familiar there. The stars are my friends… no, that’s hopelessly anthropomorphic and somewhat twee. But they are like slipping your feet into well-worn slippers, like the first bite of a recipe you’ve perfected by countless trial-and-error meals, like holding a book whose spine has been softened through years of reading and re-reading.

I’m comfortable with the sky. I’m at home there. When I stand in my yard and look up, my heart sings and my mind reaches out. My weekly chore was interrupted, delayed, but it didn’t matter.

I don’t know what your own passion is. But I will say this, and you hear me well: no time is wasted spent under the stars. And no time is wasted spent doing what you love.

Picture credit: Il conte di Luna’s Flickr photostream, used under the Creative Commons license.

What does it look like to stare into infinity? Like this:

Oh yes, you need to click that to see it in its glory. Because there’s a lesson here…
(more…)

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