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Articles tagged with "paranal"
A half hour exposure reveals a string of stationary lights over Paranal, strung out roughly along the celestial equator. They are all geostationary satellites, orbiting at an altitude of 36,000 km where it takes exactly 24 hours to orbit the Earth.
The Next Generation Transit Survey is being commissioned at Paranal. It will consists of 12 small telescopes, all operating remotely to search for planets around other stars. I went over there to take some photos as they were preparing for their official first light.
It’s very dark at Paranal but there’s still background light that we can’t do anything about: the atmosphere itself glows at night. It can be surprisingly bright. Often it’s green, when oxygen atoms are glowing. It can be red, too, when nitrogen is responsible. And it can be orange, when sodium atoms are being excited. Tonight, it was extremely orange, looking a lot like streetlights on clouds, except there were no clouds, and there are definitely no streetlights near here. It got really strong while I was taking a time lapse and you can see huge waves in the upper atmosphere rippling.
The Milky Way is at the right, and the Milky Way’s two satellite galaxies, the Magellanic Clouds, are in the middle of this photograph. There was a lot of airglow to the south west, and just to the right of the Large Magellanic Cloud you can see the distant glow from the town of Taltal.
The beautiful southern Milky Way, shining brightly over the four telescopes of the VLT, and the VST in the distance.
The Milky Way crosses the sky over two of the Auxiliary Telescopes. The sky looked pretty dark to the naked eye but in the long exposure it turned out to be full of strong red airglow. Around sunset, there are usually lots of satellites visible crossing the sky, and a few can be seen in this photo.
In the late evening twilight just before the start of proper darkness, the centre of the galaxy rises behind UT4.
The centre of the galaxy passes right over Paranal. We take great care to avoid stray light that could affect our observations, but this photo contains damning evidence – someone left the lights on in the VLTI control room.
Paranal is very dark, but there are some sources of light pollution we can’t do anything about. 80 miles north is the city of Antofagasta, which showed up more clearly than usual in this photo because of low cloud reflecting the street lights. And a similar distance up is the upper atmosphere, which glows faintly at night. Further afield, dust particles in the solar system reflect sunlight and cause the faint white band that stretches up from the horizon. The handle of the Plough is visible just above Antofagasta – a far northern constellation that we can just about see from down here.
The centre of the Milky Way is rising next to UT4 in this photo, with Alpha and Beta Centauri and the Southern Cross high over the VLTI control room, inside which an insanely complicated system of mirrors and lenses can combine the light from four telescopes to study objects in incredible detail.
A view from out the back of the residencia, where you can see the southern stars trailing to the right, and the northern stars trailing to the left.
The Magellanic Clouds are satellite galaxies of the Milky Way. Mapuche mythology says that today there is a large one and a small one, but there used to be three large ones. One disappeared, one is on the way out, and the third one is still complete for now, but when it too runs out, the universe will end.
Just after sunset, you can usually see a dark band above the horizon with a red band of colour above it. This is the shadow of the Earth on the atmosphere, with the last of the daylight scattering off the dust in the air higher up. It’s sometimes called the Belt of Venus.
Spotting Hubble going over is always nice. It’s not so easy to see – you can’t miss the International Space Station when it goes over, but Hubble is much smaller and fainter. It also orbits a bit lower so it’s often crossing the sky in twilight. Tonight, though, it was already quite dark when I caught it going over UT3
Star trails over two of the four telescopes which make up the VLT. To make this image I stacked 750 individual photos, each one a 20s exposure at ISO 400, using a 24mm lens at f/1.4.
Everyone’s favourite southern constellation over two of the telescopes at Paranal, with the Coalsack Nebula, the Eta Carina nebula, and the two Magellanic Clouds also visible.
UT4 is equipped with a laser. It creates an artificial star from which the way the atmosphere is moving can be measured, and then corrected for in real time by distorting the telescope mirror. It’s incredible technology which allows amazingly sharp images to be taken, and it also looks extremely cool from out on the platform.
No sunspots to be seen on the sun’s surface today, but at least a turbulent atmosphere made it go crazy shapes at sunset.
Solar activity has been unusually low recently but today there were some nice sunspots visible at sunset. I didn’t use a filter for this photograph – my very slow 400mm f/5.6 lens plus the thickness of the atmosphere between me and the sun at sunset did the job well enough.
Normally when making star trail photographs, I take lots of short exposures and stack them together. Today I tried it the old fashioned way just for a change, and did a single exposure for two and a bit hours – the battery ran out before it got to the intended three hours. The benefit of doing it this way was that geostationary satellites show up in the long exposure as bright spots along the celestial equator.
My photography set up is not very good for moon shots – I use a very old and cheap Olympus 400/5.6 lens with Canon adapter, and the lens has awful contrast and sharpness. But with some luck and some post processing, the moon still comes out OK.
The fabled green flash happens sometimes when the atmosphere refracts the sun’s light in just the right way at sunset. I watch the sunset every single night that I’m at Paranal, unless there’s something I have to be doing at that moment, and usually the sun sets with no hint of green. People on the platform usually say something about how they see it much more often at La Silla, but I didn’t see it there either.
Tonight, I didn’t see the flash by eye, but I caught it on camera nevertheless. A strip of green floated above the rest of the orange disk, too faint for me to notice it but there without any doubt.
A view south with airglow of different colours – red from nitrogen gas, green from oxygen, all glowing faintly in the upper atmosphere.
Paranal does the majority of its work in service mode, where we, the observatory staff, carry out observations that have been requested and designed by other astronomers. This has the advantage that if they need certain weather conditions, then we simply wait until we have conditions as good or better than needed and take the observations then. But for the astronomers to come and carry out their own observations also has its advantages – they can see much better how the observatory works, and make sure the data is exactly as they want it. But though the weather is good here at least 90 per cent of the time, there’s still a chance that a visitor will get no data at all. That happened tonight, and it was sadder than usual because it was Christmas night. People had travelled thousands of miles to be away from friends and families, in the hope of better understanding some of the mysteries of the universe in compensation, but it was cloudy for most of the night and we couldn’t do any observing at all.
Long after sunset but still before the sky was properly dark, Orion was setting over the telescopes. The orange glow on the horizon comes from the Escondida copper mine 90 miles away.
Not a great night for astronomy with lots of thin cloud passing, but we could still observe. I went out and did some photography in the small hours of Christmas morning, and the Moon briefly shone through the shutters of UT4 as it set behind the cloud.
Novae are explosions that happen on certain types of stars. The star gets up to a million times brighter than it was, but they are quite rare and years can go by without a nova being visible to the naked eye. Nova Centauri 2013 exploded on 2 December 2013, and was easily visible to the naked eye at its brightest. It was quite strange to see Alpha and Beta Centauri joined by a third star that’s not normally there.
Clouds passing over made it a difficult night for observations. The airglow was unusually strong to the south – still almost invisible to the naked eye but strong enough to look like the aurora borealis on a long exposure photograph. This was a 30s exposure at ISO 6400.
Venus was very close to the galactic centre when I took this photo. A bit of green airglow can be seen low down, and stretching upwards from the Milky Way is the zodiacal light, sunlight scattered by dust particles in the solar system.
We finished our epic Chile journey with a visit to Paranal where I spend 80 nights a year working at the telescopes. We had some bad luck though. The skies are normally clear here at least 90 per cent of the time, but the last couple of years have seen quite a lot of bad weather, and today we managed to pick a cloudy day. We’d seen the cirrus over the desert as we headed out from Antofagasta, but there is quite often cloud nearer to Antofagasta while Paranal is clear. Today it was not so, and the clouds thickened during the afternoon.
By nightfall they’d decided not to open the telescopes. The opening is always impressive to see, so this was a pity, but the engineer who would have opened the dome treated us to a good display anyway, tilting and rotating the telescope so that we got great views of it inside the closed dome.
We went out onto the platform in the night, and through breaks in the clouds we could see stars, but nothing like the normal blazing skies. It was a pity, as I’d planned the trip for a time when there would be no moon and the centre of the Milky Way would be high in the sky at the start of the night. The night before, and the night after, there wasn’t a cloud in the sky.
But Paranal is not only about the night skies. We went for a walk in the desert the next day, and that’s always great. The terrain here is so harsh that just before we arrived, they’d been testing a Mars rover nearby.
From my native latitudes the centre of the galaxy is not visible. The first time I saw it, it blew me away, and it still does.
After my interrupted sleep I wasn’t looking forward to my first night unsupervised at the controls, but in the end it was postponed again. Early the next afternoon the decision was taken that the telescopes would not open at all that night, to avoid any possibility of water getting in. The “domes” have flat tops and any standing water could spell disaster for all the sensitive mechanics and electronics.
So we went up to the control room anyway but no astronomy would be done tonight. It was a pity, because the skies after the storm were stunningly clear. With the luxury of having no observatory work to do, I went out on the platform late in the night to appreciate the view.
I moved here in October, at which time the centre of the Milky Way is setting and can’t be seen very well. Now, for the first time, I got a good look at it. It’s stunningly bright and you can only see it well from the Southern Hemisphere. This is a real shame for the 90% of the world’s population who live in the Northern Hemisphere – their view of our home galaxy is completely inadequate in comparison. I hadn’t really seen it properly since I was in Zambia, 11 years ago. So I was really happy to see it again tonight, rising behind the telescopes in the small hours. It will be visible for the next few months, and I will be taking a lot more photographs of it.
After four nights of this shift, one had been completely lost and three partially lost to bad weather. The fifth was my first night as a trained night astronomer. Crunch time. Would I mess it up? Would I break the telescope? Fortunately it turned out I wouldn’t, because the night was also completely lost, with thick clouds and high humidity ruining any chance of doing any astronomy. I was slightly relieved.
I went out on to the telescope platform a few times. Lightning was flickering some way inland, but I assumed the storm would not come out our way. Since I moved to Chile in September 2011, I had hardly seen any rain at all. There was an evening of drizzle in October, and I felt a few spots, literally no more than 10 or so, in January. Otherwise, nothing, and my English soul was in need of watering. But up here in the Atacama, I didn’t think it was going to get any. So when I went out on to the platform again at 5am and actually felt spots of rain, I didn’t really believe it was rain. I just thought it was extreme humidity.
We gave up a couple of hours before dawn when it was obvious the weather wasn’t going to improve. I went to bed at about 7am. Then, at 9am, I was woken up by thunder. Blearily I got to my feet. Thunder? Surely not? And what was this sound, something like rain battering on the window. In disbelief I rolled up the blind and saw that it was true – an epic downpour was in progress. Still half asleep, I went out into the corridor of the residencia and found rain pouring through the roof. The building appears not to be even slightly waterproof.
I was just stunned. I hadn’t expected to see anything like this here in the driest desert on Earth. They tell me it does rain here, sometimes, but the last time had been only eight months ago. I’d thought, during the long dry summer, that when I did finally experience rain again, I might go out and stand in it and enjoy it. But after two hours sleep I was so tired that I just went back to bed, and slept through the rest of the storm once the thunder had stopped.
For a couple of days afterwards, water was still dripping through the ceiling.
I’m at Paranal right now, undergoing my final training before they let me fly solo at the controls of the world’s premier optical observatory. My training so far has been seriously affected by weather – of the 11 nights I’ve done, five have been completely lost and most of the rest have been partly lost. Last night the telescopes were closed a couple of hours early, and tonight we didn’t open at all. The telescopes have to be closed when the humidity goes above 60%, and tonight it was nearly 100% and there were clouds right on the peak.
Before the clouds came in, though, I went out to take a photo of the night sky. The moon was rising, and Orion was setting. When I took the photo, I couldn’t see the shadow the moon was casting, so I was pretty amazed when I looked at the camera screen to see the shadow of the telescopes, cast on to the clouds below.