A small rock in the Atlantic

All about the island of La Palma, in the Canaries.

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Saturday, 5 April 2008

SuperWASP, the Planet-Hunter

Most of the telescopes at the observatory here look spectacular even from the outside. SuperWASP looks like a big garden shed. It's the white thing at bottom left.

Even when it opens up, it still doesn't look like a professional telescope. To me, it looks more like a small missile launcher.

The equipment isn't that spectacular either. As modern telescopes go, it was built for peanuts. It has eight cameras, each with a Canon 200mm f/1.8 lens and a 2048 x 2048 pixel CCD. Most professional telescopes have the digital camera cooled by liquid nitrogen, to keep them down to about -170ºC. The colder they are, the less grainy the picture is. SuperWASP has peltier cooled cameras working at -50ºC, like a really dedicated amateur.

The spectacular bit it the results. WASP stands for "Wide Angle Search for Planets". It's found ten new planets in the last six months. These aren't in our Solar System. They're orbiting other stars. The three they netted last year made Time magazine's the "Top Ten Science Discoveries of 2007".

It's quite a trick to find an extra-solar planet, because they don't shine themselves. True, they reflect light, just as Mars and Jupiter do, but that's only about 1/1,000,000th of the light of the parent star. It's like trying to spot a candle flame beside a tactical nuke. The first extra-solar planets were found by looking for stars wobbling as a large planet orbited close in.

Image: Wikipedia

But this only works for unusually large planets, unusually close in.

SuperWASP uses the transit method. It tries to spot a star getting 1% dimmer as a plant passes in front of it, blocking some of the light. This is a bit like trying to catch a spotlight getting dimmer as an ant crawls across it. And of course it only works if the planet's orbit is edge-on to us. But the great advantage of superWASP is that looks at 100,000 stars per camera per photo. Eventually they have to strike oil.

Lightcurve animation of a transit in HD209458, from Queen's University, Belfast, UK.

The catch is that you can't possibly look at 50Gb of data per night by hand. Computers take care of the routine part automatically, and produce a list of stars with fluctuating brightness. Then someone at either the Nordic Optical Telescope on La Palma, the Swiss Euler Telescope in Chile or the Observatoire de Haute Provence in southern France tries to catch the star wobbling. It it's wobbling and dimming in snych -- bingo!

I still can't believe this works so well. And the really cool bit is that I used to know the team's leader, Dr Don Pollaco.

If you want to know more, see

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Thursday, 3 April 2008

Prehistoric Rock Carvings

The people who lived here before the Spanish invasion in 1493 were called Benauaritas. Since they didn't have writing, not all that much is known about them, and what there is comes from the invaders. Not exactly an unbiased source!

Their technology was pretty basic, maybe because the climate in La Palma is kind enough not to encourage things like weaving. They wore skins, lived mostly in caves, herded goats and grew barley. They also collected things like shellfish and wild dates. There were fourteen tribes on La Palma, and each tribe had its own territory. The modern municipalities roughly correspond to the old kingdoms. Much of their history and culture has been lost.

But they did leave behind rock carvings. These are inside the Caldera de Taburiente, but there are far more spectacular ones at La Zarza (in Garafía) and Belamaco (in Mazo). Archaeologists believe that they poured a libation of goats' milk onto the stone, which would flow down the channel, making its shape stand out clearly.

I have a very strange mind. It looks to me as though the stone is imprisoned, presumably because it's dangerous.

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Tuesday, 1 April 2008

Artesanía Christina

I love Christina's shop. She started off in the local flea market, selling fancy knitting yarn in the most wonderful colours. I always wanted to buy the lot and spend the next year knitting. Now she has a shop on the Calle Real, still selling the yarn, but also finished knitware and costume jewelry which she makes herself out of local lava and coral, with silver or gold-plated silver mountings.

Knitters: the yarn is best knitted on 10 mm needles (also on sale) so you finish quickly. And she has free pattern booklets.

She opens mornings from Monday to Saturday from 10 am to 2 pm, and Monday to Friday afternoons from 5pm to 8 pm. She speaks good English.

Everybody calls the main street in Santa Cruz de la Palma, "the Calle Real", but nowhere along it's length is there a street sign with that name! I used to suspect that the whole thing was invented to confuse visitors, but now I know better. It's called the Calle Real (Royal Road) because it's the one the Kings come along to visit baby Jesus each January 5th.

The southern end of the Calle Real (from the post office to Avenida El Puente) is called Calle O'Daly, and the northern end (Avenida El Puente to Plaza Alemeda) is Perez de Brito. Christina's shop is at Perez de Brito, 28, just south of the Placeta.

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