Blogs / Bad Astronomy

Wildfires are sweeping through the country right now. A mixture of high temperatures, low humidity, and low rainfall has created terrible conditions; I’m surprised none has started where I live (though it did rain a bit last week).

In southern California, specifically LA, a huge fire tore through Griffith Park, a lovely area in the heart of LA. Sitting atop a hill there is the venerable Griffith Park Observatory. Built in 1935, it just underwent a $90+ million expansion and renovation.

It was in serious danger from the fire, but it appears to be OK (you can see dramatic images of it on Flickr, like the incredible image above). I’ve been keeping an eye on this… in November of 2004 I was in Australia on a speaking tour, invited by the National Skeptics for their annual conference. I had an amazing, tremendous, bonzer time. I love the area, the people, the coffee, just everything there.

But there was one somber moment. With some friends I toured four world-class observatories down there, including Mt. Stromlo, which is near Canberra, the Ozzie capital city. In January 2003, a fire of apocalyptic proportions burned in the Canberra hills, and in this case there was no happy ending: the observatory was almost totally destroyed.

When I toured the area, it was still completely ravaged. There were burned trees everywhere, live oaks and eucalyptus, the same kind we have in northern California (the whole area was strikingly similar to Sonoma County, in fact, which was very disconcerting — I’d just be thinking how much it looks like home, when a pack of wallabies would hop across the road). And the observatory… oh, the observatory.

The domes were destroyed. Some had collapsed, some had been taken away. In one, the mount structure for the telescope was still inside, and they wouldn’t let anyone in. There were many tons of unstable steel in there.

I could see paint peeled away from the metal domes due to the intense heat of the fire.

And then we went to the 50 inch.

I knew this telescope. I had never used it, but I have friends who had, and I’d seen pictures of it in happier days. How many papers on the MACHO project had I read, observations done on this grand old lady? But not any more. The telescope, like many big instruments, was an open truss structure. Steel pipes had held the mirror in place, but the fire had softened them, and the whole thing had swung down. Bizarrely, the mirror hadn’t melted: the glass had shattered in place. We walked right up to it, and we could still see that it held a parabolic shape, but instead of one piece of glass, it was now several thousand, like someone had taken a hammer to it.

One piece near me stuck up a bit, and without thinking I reached over and pulled it out. It was maybe three inches long, and one end came to a wicked point. I just stared at it, and our guide told me I could keep it. I remember just staring at it… I still have it. It’s packed away, ready to move to Colorado, or else I’d put up a picture of it. I keep it around to remind me that sometimes, solidity is an illusion.

Still, you can’t keep Australians down. I wouldn’t even hope to try! They’re rebuilding the observatory, of course. I just can’t say enough good things about Australians, including them having their heads screwed on straight — well, most of ‘em do. But that crazy upside-down place is enough to turn anyone into a drongo.

So. I’m glad that Griffith Observatory is out of danger. I’m not sure I can take the destruction of another wonderful place where people get a chance to touch the stars.

Artist’s conception of the planet HD189733b.

Wow, more cool extrasolar planet news.

Using the Spitzer Space Telescope, astronomers have been able to make, for the very first time, a (very crude) map of the super-Jupiter orbiting the star HD 189733, about 60 light years away. The planet was discovered in 2005 (note this is not the new "Earthlike" planet found recently, this is a big gas giant like Jupiter) and is one of a handful that passes directly in front of its star as seen by us on Earth. In other words, it transits the star, making a little eclipse once per orbit.

Transiting planets are very useful: by measuring how much the starlight drops, we can measure the size of the planet! The bigger the planet, the more the light from the star dims. This gives us a direct measurement of the planet’s radius.

But it also allows a cool technique to measure features on the planet, too. Imagine there is a really bright spot smack dab in the middle of the planet. As it orbits the star, the planet gets blocked by the star. We see the total system brightness drop (because the planet contributes a little bit of light). But when the bright spot gets blocked, the brightness would make a sudden dip. And if instead of a bright spot, we had a dark spot, when it got covered by the star, the brightness would not drop as quickly.

So by very carefully measuring the way the brightness changes as the planet goes behind the star, we can actually make crude maps of planetary features, even though the planet itself is far too small to resolve into a disk. This technique has been used to make maps of Pluto and its moon Charon, in fact.

But doing it for an extrasolar planet is a bit tougher! They are incredibly dim, and the stars very bright. But it’s possible, and so Heather Knutson, a graduate student (!!) at the Center for Astrophysics and her team did just that using Spitzer! Voila:

Like I said, the map is crude (yet it represents 33 hours of observations and a quarter million data points!), but it does show one obvious feature. Spitzer measures infrared light, so brighter objects in this case are warmer. That bright spot is a hot spot they found, which is roughly twice the size of Jupiter’s Great Red Spot (which itself is several times bigger than Earth!). As it happens, the planet spins once for every time it goes around the star, so it always shows the same face to its star (the same way the Moon always shows the same face to Earth). So you might expect the hottest part of the planet to be right under the star, where the star is always directly overhead. But that’s not the case; the hot spot is actually about 30 degrees away from the "substellar point". Knutson speculates that this is due to winds on the planet; a sort of alien jet stream. That sounds plausible to me.

At the moment this is the best map that can be made. But over time, as they make more observations, it is possible to improve on this map. Are there other warm spots? Are there cool spots? Can we learn more about the big spot? After all, all we know is its rough size and where it is, but not its shape. That might be possible to determine, though I can’t imagine how difficult the observations would be!

This is a fantastic step forward, and it makes me even more excited to think about what we might learn in the next few years. It takes advanced technology, but it also takes clever people to figure out how to use it to its best advantage. As it happens, we have both.