A small rock in the Atlantic

Stargazing

The island's association of amateur astronomers will be holding a star party on Saturday, from 8pm, behind the trees in the plaza beside the tourist office in El Paso. There will be lots of amateur telescopes there, so you can get a good look at, say, Saturn or Jupiter, and they plan to be there until midnight. I gather they speak some English.

La Palma has amazing skies. This is a great opportunity, especially if you live in a big city where the street lights drown out the stars.

For information phone Toño Gonzalez on 607592175.

Labels: astronomy, El Paso, La Palma, La Plama, telescopes

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The William Herschel Telescope

The William Herschel Telescope at sunset.

The William Herschel Telescope is currently the biggest and best optical telescope in Europe (until GranTeCan opens this autumn.) The main mirror is 4.2 m across (165", or 13' 9") which astronomers call "a good light bucket". It's rather old as world-class telescopes go, since it opened in 1987, but it still produced excellent science. In fact data from the WHT has been used for about 1,500 scientific papers. It helps that it's been fitted with adaptive optics.

This is when you use some starlight to measure the air turbulence, and then deform a special, flexible mirror to compensate for that turbulence. It's rather like using glasses to correct for the shape of your eyeball, but these glasses change shape 100 times a second.

This only works if you have a bright star handy, in order to measure the turbulence in the first place. Some parts of the sky have far more stars than others, so the WHT has a laser, which can be used to create an artificial star. To the best of my knowledge, it's the only one working in Europe (although GranTeCan will have one too.)

The telescope's named after Frederick William Herschel, who was born in Germany but emigrated to England. He started life as a musician, but music lead to mathematics and then to astronomy. He's best known for discovering the planet Uranus, but he also measured the height of the mountains on the moon, discovered double stars, catalogued loads of nebulas, found two of Saturn's moons and two of Uranus's moons, and was the first to realise that the solar system is moving around the galaxy. Oh, and he discovered infra-red radiation.

Pretty impressive for someone who didn't really get started on astronomy until his mid-forties. (Obviously there's hope for me yet.)

If you want to visit the WHT, you have to sign up in advance for an open day. Details at: http://lapalmaisland.sheilacrosby.com/articles/visit_obs.php

Inside the William Herschel Telescope, beside the secondary mirror.

Labels: astronomy, La Palma, La Plama, observatory, Roque de los Muchachos, telescopes, William Herschel Telescope

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Observatory Open Days for 2008

Traditionally, the observatory has been open to visitors about 4 days per year, with perhaps 6 groups for each day. This year, they're going to have 20 open days, but most of them will only have one group. Each visit starts at 9:45 with a visit to the MAGIC gamma-ray telescope, followed by one other telescope, and finishes before 12.00.

DATE	Day	2nd telescope
8th July	Tues	WHT or INT
10th July	Thursday	Galileo
12th July	Saturday	GranTeCan
15th July	Tues	Mecator and Liverpool
17th July	Thursday	Galileo
19th July	Saturday	GranTeCan
22nd July	Tues	WHT or INT
24th July	Thursday	Mecator and Liverpool
26th July	Saturday	GranTeCan
29th July	Tues	WHT or INT
31st July	Thursday	Galileo
7th August	Thursday	Galileo
12th August	Tuesday	WHT or INT
14th August	Thursday	Galileo
15th August	Friday	GranTeCan
19th August	Tuesday	WHT or INT
21st August	Thursday	GranTeCan
22nd August	Friday	Garafía residents only
26th August	Tuesday	Mecator and Liverpool
28th August	Thursday	Mecator and Liverpool
30th August	Saturday	WHT and Galileo

Friday 15th of August and Saturday 30th August will have several groups.

Visits must be booked in advance, by calling the receptionist at the Institute of Astronomy on (00 34) 922 425703 And yes, the receptionist speaks English. Book early -- most of the places for July have gone already.

Labels: La Palma, La Plama, observatory, open days, Roque de los Muchachos, telescopes

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The MAGIC telescope

This is the MAGIC telescope (Major Atmospheric Gamma-ray Imaging Cherenkov Telescope). It's perhaps the most exotic telescope at the observatory at the Roque de los Muchachos.

It's not an optical telescope. Instead of observing visible light, it's looking for gamma rays. Visible light is made up of different wavelengths, which give the different colours from red to violet. Wavelengths which are just a bit too short to see form ultra-violet (the stuff that gives you sunburn). Even shorter lengths are X-rays, and the shortest of all are gamma rays. The snag is that gamma rays don't get through the earth's atmosphere. But as they break up, they create a cascade of particles in the upper atmosphere, and the telescope is looking for these. By looking at the cone of atomic debris, the scientists can work backwards and find out which direction the gamma ray was coming from.

The nearer "basket" won't be operational until next year, but the father "basket" is already going strong. Instead of one big mirror, it has over 1,000 mirrors, each 50cm square, to form a compound mirror 17m (56 ft) across. That's the biggest telescope mirror in the world.

So where do gamma rays come from?

Some come from active galactic nuclei. These are the centres of distant galaxies, which are strangely bright. Astronomers believe this is because there's a super-massive black hole gobbling up the nearby stars. But they don't really understand the details, which is why they're keen to study them.

Supernova remnants are another source of gamma rays. When a large star runs out of its atomic fuel, it creates a massive explosion. Supernova remnants are the smoking gun, and the best available clue to understand supernovas. (Our own star is too small to explode in this way. Eventually it'll just fizzle out, but we have about four billion years before that happens.)

And the final source is gamma ray bursts. These are mysterious bursts of energy, which last anything from twenty seconds to two minutes. There's an orbiting satellite which watches out for them, and alerts the much larger, earth-based telescopes when it sees one. When that happens, MAGIC immediately turns to look at it. It's amazingly nimble for such a huge telescope. The whole basket weighs about 60 tons, but it can slew to point at any part of the sky within twenty seconds.

Arthur C. Clark once said that any sufficiently advanced technology was indistinguishable from magic. So you could say that MAGIC is magic.

Labels: astronomy, Canaries, Canary islands, La Palma, telescopes

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The Observatory

Twinkling stars are pretty, but astronomers would much rather they didn't. The twinkle is caused by movement in the air above you (the same as a mirage on very hot days) and it stops the astronomers getting a clear view. The Hubble Telescope gets such wonderfully clear images because it's out of the atmosphere altogether. But there's only one Hyubble, and it cost a fortune.

So they build ground-based telescopes wherever the airflow is really smooth, which means that the stars twinkle less. Of course, they also need to be away from city lights and clouds. The three best places in the world are La Silla in Chile, Mauna Kea in Hawaii, and the Roque de los Muchachos on La Palma. They each have observatories.

The La Palma observatory has twelve operational telescopes. From the largest aperture to the smallest, they are:

• MAGIC (17 m) a gamma-ray imaging Cherenkov telescope, which has the biggest telescope mirror in the world.
• William Herschel Telescope: (4.2 m) reflecting telescope
• Telescopio Nazionale Galileo: (3.5 m) reflecting telescope
• Nordic Optical Telescope: (2.56 m) reflecting telescope
• Isaac Newton Telescope: (2.5 m) reflecting telescope
• Liverpool Telescope: (2.0 m) robotic telescope (also reflecting)
• Mercator Telescope: (1.2 m) reflecting telescope
• Swedish Solar Telescope: (1.0 m) refracting vacuum solar telescope (the best in the world)
• Jacobus Kapteyn Telescope: (1.0 m) reflecting telescope
• Dutch Open Telescope: (0.45 m) reflecting solar telescope
• Carlsberg Meridian Telescope: (0.18 m) refracting telescope, used for measuring star positions.
• SuperWASP: (8 wide angle cameras with 0.11 m diameter lenses) surveying for extra-solar planets.

Plus GranTeCan (pictured), which is under construction and which has a huge 10.4 m mirror.

Labels: astronomy, Canaries, Canary islands, La Palma, telescopes

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Snow

So here we are in this lovely sub-tropical island, land of eternal spring. And the top of the mountain is covered with snow.

Last night's rain turned into a storm, with far too much thunder and lightning to sleep through. It went on for hours.

And this morning, I could see snow on the mountain. Not just the peak (the Roque de los Muchachos at 2426 m or 7,959 ft), which was covered in cloud, but much lower down, too.

Of course, we only ever get snow at high altitude, and these days, we don't get snow every winter. But when it snows, it can dump several feet in one night.

The Roque is one of the three best sites in the world for astronomy, so there's a major international observatory up there. Of course, they expect occasional snow, so they're geared up for it. They have 4x4 vehicles, and in winter they carry snow chains and shovels, just in case. Unless it's cloudy, they carry right on observing.

This is the Isaac Newton Telescope, looking Christmassy.

Labels: astronomy, Canaries, Canary islands, La Palma, telescopes