Scholars with a variety of astronomical instruments, from Peter Apian’s Instrument Buch, 1533. Apian published a number of books in the early 16th century on scientific topics ranging from geography to cosmography.
An astrolabe is an elaborate inclinometer, historically used by astronomers, navigators, and astrologers. Its many uses include locating and predicting the positions of the Sun, Moon, planets, and stars, determining local time given local latitude and vice-versa, surveying, triangulation, and to cast horoscopes. It was used in classical antiquity, the Islamic Golden Age, the European Middle Ages and Renaissance for all these purposes. In the Islamic world, it was also used to calculate the Qibla and to find the times for Salat, prayers.
The history of the astrolabe begins more than two thousand years ago. The principles of the astrolabe projection were known before 150 B.C., and true astrolabes were made before A.D. 400. The astrolabe was highly developed in the Islamic world by 800 and was introduced to Europe from Islamic Spain (al-Andalus) in the early 12th century. It was the most popular astronomical instrument until about 1650, when it was replaced by more specialized and accurate instruments. Astrolabes are still appreciated for their unique capabilities and their value for astronomy education.
Click on the images to see the dates when these astrolabes were made, and the places where they were found.
The Jantar Mantar is a collection of astronomical instruments, built by king Sawai Jai Singh in Jaipur, India between 1727-1734.
“The observatory consists of fourteen major geometric devices for measuring time, predicting eclipses, tracking stars’ location as the earth orbits around the sun, ascertaining the declinations of planets, and determining the celestial altitudes and related ephemerides. Each is a fixed and ‘focused’ tool. The Samrat Yantra, the largest instrument, is 90 feet (27 m) high, its shadow carefully plotted to tell the time of day. Its face is angled at 27 degrees, the latitude of Jaipur. The Hindu chhatri (small cupola) on top is used as a platform for announcing eclipses and the arrival of monsoons.” Wikipedia
The telescope big enough to spot signs of alien life on other planets
Engineers are about to blast away the top of a Chilean mountain to create a site for the European Extremely Large Telescope. It will allow us, for the first time, to directly observe planets outside the solar system.
An artist’s impression of the European Extremely Large Telescope (E-ELT).
Cerro Armazones is a crumbling dome of rock that dominates the parched peaks of the Chilean Coast Range north of Santiago. A couple of old concrete platforms and some rusty pipes, parts of the mountain’s old weather station, are the only hints that humans have ever taken an interest in this forbidding, arid place. Even the views look alien, with the surrounding boulder-strewn desert bearing a remarkable resemblance to the landscape of Mars.
Dramatic change is coming to Cerro Armazones, however – for in a few weeks, the 10,000ft mountain is going to have its top knocked off. “We are going to blast it with dynamite and then carry off the rubble,” says engineer Gird Hudepohl. “We will take about 80ft off the top of the mountain to create a plateau – and when we have done that, we will build the world’s biggest telescope there.”
Given the peak’s remote, inhospitable location that might sound an improbable claim – except for the fact that Hudepohl has done this sort of thing before. He is one of the European Southern Observatory’s most experienced engineers and was involved in the decapitation of another nearby mountain, Cerro Paranal, on which his team then erected one of the planet’s most sophisticated observatories.
The Paranal complex has been in operation for more than a decade and includes four giant instruments with eight-metre-wide mirrors – known as the Very Large Telescopes or VLTs – as well as control rooms and a labyrinth of underground tunnels linking its instruments. More than 100 astronomers, engineers and support staff work and live there. A few dozen metres below the telescopes, they have a sports complex with a squash court, an indoor football pitch, and a luxurious 110-room residence that has a central swimming pool and a restaurant serving meals and drinks around the clock. Built overlooking one of the world’s driest deserts, the place is an amazing oasis. (See box.)
Now the European Southern Observatory, of which Britain is a key member state, wants Hudepohl and his team to repeat this remarkable trick and take the top off Cerro Armazones, which is 20km distant. Though this time they will construct an instrument so huge it will dwarf all the telescopes on Paranal put together, and any other telescope on the planet. When completed, the European Extremely Large Telescope (E-ELT) and its 39-metre mirror will allow astronomers to peer further intospace and look further back into the history of the universe than any other astronomical device in existence. Its construction will push telescope-making to its limit, however. Its primary mirror will be made of almost 800 segments – each 1.4 metres in diameter but only a few centimetres thick – which will have to be aligned with microscopic precision.
It is a remarkable juxtaposition: in the midst of utter desolation, scientists have built giant machines engineered to operate with smooth perfection and are now planning to top this achievement by building an even more vast device. The question is: for what purpose? Why go to a remote wilderness in northern Chile and chop down peaks to make homes for some of the planet’s most complex scientific hardware?
The answer is straightforward, says Cambridge University astronomer Professor Gerry Gilmore. It is all about water. “The atmosphere here is as dry as you can get and that is critically important. Water molecules obscure the view from telescopes on the ground. It is like trying to peer through mist – for mist is essentially a suspension of water molecules in the air, after all, and they obscure your vision. For a telescope based at sea level that is a major drawback.
"However, if you build your telescope where the atmosphere above you is completely dry, you will get the best possible views of the stars – and there is nowhere on Earth that has air drier than this place. For good measure, the high-altitude winds blow in a smooth, laminar manner above Paranal – like slabs of glass – so images of stars remain remarkably steady as well.”
The view of the heavens here is close to perfect, in other words – as an evening stroll around the viewing platform on Paranal demonstrates vividly. During my visit, the Milky Way hung over the observatory like a single white sheet. I could see the four main stars of the Southern Cross; Alpha Centauri, whose unseen companion Proxima Centauri is the closest star to our solar system; the two Magellanic Clouds, satellite galaxies of our own Milky Way; and the Coalsack, an interstellar dust cloud that forms a striking silhouette against the starry Milky Way. None are visible in northern skies and none appear with such brilliance anywhere else on the planet.
Hence the decision to build this extraordinary complex of VLTs. At sunset, each one’s housing is opened and the four great telescopes are brought slowly into operation. Each machine is made to rotate and swivel, like football players stretching muscles before a match. Each housing is the size of a block of flats. Yet they move in complete silence, so precise is their engineering.
Building the four VLTs, which have been named Antu (Sun), Kueyen (Moon), Melipal (Southern Cross) and Yepun (Venus) in the language of Mapuche people of Chile, was a formidable challenge, needless to say. Each has a giant mirror that is 8.2 metres in diameter but only 17cm thick: any thicker, and the mirror would be too heavy to move and point. Such thinness leaves the mirrors liable to deform as temperatures and air pressure fluctuate, however, and so each has 150 actuators fitted to its unpolished side. These push the mirrors to keep them within a few billionths of a centimetre of their proper shape. In addition, ESO astronomers use a laser-based system known as adaptive optics to measure turbulence in the upper atmosphere and to change each telescope’s internal mirror configuration to compensate for any disturbance they can measure.
The result is a cluster of astronomical devices of incredible power and flexibility, one that has been involved in an astonishing number of critically important discoveries and observations over the past decade, as ESO astronomer Olivier Hainaut explains. “Perhaps the VLT’s most spectacular achievement was its tracking of stars at the centre of the Milky Way. Astronomers followed them as they revolved around… nothing. Eventually they were able to show that something incredibly small and dark and massive lay at the centre of this interstellar waltz. This was the first time, we now know, that scientists had directly observed the effect of the supermassive black hole that lies at the heart of our galaxy.”
The Milky Way seen from the Paranal Observatory in Chile. Photograph: National Geographic Image Collec/Alamy
The VLTs also played a key role in providing observations which showed, from the behaviour of distant supernovae, that the expansion of the universe was actually accelerating thanks to the action of a force now known as dark energy. This discovery later won Saul Perlmutter, Brian Schmidt and Adam Riess the 2011 Nobel prize for physics. And in 2004 the telescopes were used to make a direct observation of an exoplanet – a planet that orbits around a star other than our Sun. It was another astronomical first. Until then scientists had only been able to infer the existence of exoplanets from the way they affected the movement of their parent star or its light output. “This was history-book material, a discovery of the same quality as Galileo’s drawings of the mountains on the moon or the satellites of Jupiter,” says Hainaut.
These discoveries have only whetted astronomers’ appetites for more, however. Hence the decision to build the £800m E-ELT – whose British funding will come through a £88m investment from the UK Science & Technology Facilities Council. Engineers have now completed a road to the mountain from Paranal and on 16 June are set to begin blasting to remove the top from Cerro Armazones. Then they will start to build the E-ELT using 798 hexagonal pieces of mirror to create a mammoth device that will be able to collect a hundred million times more light than the human eye. When completed in around 2025, the 2,700-tonne telescope will be housed in a 74 metre high dome and operated by astronomers working 20kms away in Paranal. It will be the world’s biggest eye on the sky.
An indication of the E-ELT’s potential is provided by ESO astronomer Linda Schmidtobreick. “There are fundamental issues that only a telescope the size of the E-ELT can resolve,” she says. “Its mirror will have a surface area 10 times bigger than any other telescope, which means it will take a 10th of the time to collect the same amount of light – ie the same number of photons – from an object compared with these other instruments.”
The astronomers’ residence: ‘As accommodation goes, it’s as exotic as you can get.
For Schmidtobreick, this ability to collect light quickly is crucial to her research. She studies stars known as cataclysmic variables: pairs of stars in which one is pulling vast amounts of gas, mainly hydrogen, from its companion, a process that can trigger gigantic thermonuclear eruptions, sometimes within 30 seconds or so. “With current instruments, it can take minutes or hours to collect light from these objects, which is too long to resolve what is happening,” says Schmidtobreick. “But with the E-ELT, we will be able to study many, many more cataclysmic variables because we will be able to collect significant amounts of light from them in seconds rather than minutes or hours and so will be to resolve their behaviour.”
Simone Zaggia, of the Inaf Observatory of Padua, is another frequent visitor to Paranal and has a very different reason for backing the E-ELT. He believes it will play a vital role in the hunt for exoplanets – in particular, exoplanets that are Earth-like and which could support life. “At present, our biggest telescopes can only spot really big exoplanets, giants that are as big as Jupiter and Saturn,” he says.
“But we really want to know about the smaller worlds that make up the solar systems in our galaxy. In other words, we want to find out if there are many Earth-like planets in our part of the universe. More importantly we want to find out if their atmospheres contain levels of oxygen or carbon dioxide or methane or other substances that suggest there is life there. To do that, we need a giant telescope like the E-ELT.”
This point is backed by Gilmore. “We can see exoplanets but we cannot study them in detail because – from our distant perspective – they appear so close to their parent stars. However, the magnification which the E-ELT will provide will mean we will be able to look at them directly and clearly. In 15 years, we should have a picture of a planet around another star and that picture could show its surface changing colour just as Earth does as the seasons change – indicating that vegetation exists on that world. We will then have found alien life.”
Astronomers’ amazing home
A walk down the alleyway that leads from Paranal observatory’s entrance gate into its astronomers’ residence produces one of the most striking changes in surroundings you can experience in a few footsteps. Outside the air is parched and the ground bleached by sunlight from a sky that is hardly ever troubled by clouds. Push through the double swing doors and you enter a rainforest – and a path that leads down through towering ferns and tropical plants until you reach a swimming pool in the residence’s lowest level. As accommodation goes, it’s as exotic as you can get - though hedonism was far from the minds of the architects when they designed it.
To battle the arid conditions of the air at 8,600ft-high Paranal, they wanted a way to keep it moist and fresh for the scientists staying there. The answer was a swimming pool and an indoor tropical garden that is constantly watered with supplies imported by trucks from the coast every day. Moist air from the pool and garden then circulates around the rest of the residence. The result is a building that is remarkably airy and light – until 7pm when, every night, all openings and windows, including the vast glass dome over the pool, are closed and shuttered automatically to prevent any chink of light from affecting observations made on the mountain top.
The scale and style of Paranal and its residence is extraordinary and movie producers have fallen over themselves in their attempts to film it. Most have been turned down – with the exception of the 2008 Bond film,Quantum of Solace, whose final scenes were filmed here. (In contrast the last X-Men film was turned down flat because its producers wanted to fly helicopters near the observatory’s precious telescope complex.) Given the vast cost of building and running Paranal, filming was not allowed to disturb its tight observing schedule. “I was woken up by the sound of someone repeatedly jumping on to the balcony in the room next to mine,” one astronomer recalls. “It turned out to be the actress Olga Kurylenko - who plays the film’s heroine Camille. It was quite a shock. I mean you don’t get that sort thing happening at other observatories.”
Wolf-Lundmark-Melotte : Named for the three astronomers instrumental in its discovery and identification, Wolf - Lundmark - Melotte is a lonely dwarf galaxy. Seen toward the mostly southern constellation Cetus, about 3 million light-years from the Milky Way, it is one of the most remote members of our local galaxy group. In fact, it may never have interacted with any other local group galaxy. Still, telltale pinkish star forming regions and hot, young, bluish stars speckle the isolated island universe. Older, cool yellowish stars fade into the small galaxys halo, extending about 8,000 light-years across. This sharp portrait of WLM was captured by the 268-megapixel OmegaCAM widefield imager and survey telescope at ESOs Paranal Observatory. via NASA
A part of the Jantar Mantar observatory, Jaipur, Rajasthan
From Wikipedia: “The Jantar Mantar monument of Jaipur, Rajasthan is a collection
of nineteen architectural astronomical instruments, built by the Rajput
king Sawai Jai Singh, and completed in 1738 CE. It features the world’s largest stone sundial, and is a UNESCO World Heritage site.”
Straight out of the camera. Posted for No Edit Friday.
OUT -OF -THIS -WORLD FIRST -LIGHT IMAGES EMERGE FROM GEMINI PLANET IMAGER
After nearly a decade of development, construction and testing, the world’s most advanced instrument for directly imaging and analyzing planets orbiting around other stars is pointing skyward and collecting light from distant worlds.
“Even these early first-light images are almost a factor of 10 better than the previous generation of instruments. In one minute, we were seeing planets that used to take us an hour to detect,” says Bruce Macintosh of Lawrence Livermore National Laboratory, who led the team who built the instrument.
For the past decade, Lawrence Livermore has been leading a multi-institutional team in the design, engineering, building and optimization of the instrument, called the Gemini Planet Imager (GPI), which will be used for high-contrast imaging to better study faint planets or dusty disks next to bright stars. Astronomers – including a team at LLNL – have made direct images of a handful of extrasolar planets by adapting astronomical cameras built for other purposes. GPI is the first fully optimized planet imager, designed from the ground up for exoplanet imaging deployed on one of the world’s biggest telescopes, the 8-meter Gemini South telescope in Chile.
Probing the environments of distant stars in a search for planets has required the development of next-generation, high-contrast adaptive optics (AO) systems, in which Livermore is a leader. These systems are sometimes referred to as extreme AO.
Macintosh said direct imaging of planets is challenging because planets such as Jupiter are a billion times fainter than their parent stars. “Detection of the youngest and brightest planets is barely within reach of today’s AO systems,” he said. “To see other solar systems, we need new tools.”
And those new tools are installed in the Gemini Planet Imager with the most advanced AO system in the world. In addition to leading the whole project, LLNL also was responsible for the AO system. Designed to be the world’s “most sophisticated” astronomical system for compensating turbulence in the Earth’s atmosphere – an ongoing problem for ground-based telescopes – the system senses atmospheric turbulence and corrects it with a 2-centimeter-square deformable mirror with 4,000 actuators. This deformable mirror is made of etched silicon, similar to microchips, rather than the large reflective glass mirrors used on other AO systems. This allows GPI to be compact and stable. The new mirror corrects for atmospheric distortions by adjusting its shape 1,000 times per second with accuracy better than 1 nanometer. Together with the other parts of GPI, astronomers can directly image extra-solar planets that are 1 million to 10 million times fainter than their host stars.
GPI carried out its first observations in November 2013 – during an extremely smooth debut for an extraordinarily complex astronomical instrument the size of a small car. “The GPI team’s huge amount of high quality work has begun to pay off and now holds the promise of many years of important science to come,” said LLNL Project Manager David Palmer.
For GPI’s first observations, it targeted previously known planetary systems – the 4-planet HR8799 system (co-discovered by an LLNL-led team at the Gemini and Keck Observatory in 2008) and the Beta Pictoris system, among others. GPI has obtained the first-ever spectrum of the very young planet Beta Pictoris b.
The first-light team also used the instrument’s unique polarization mode – tuned to look at starlight scattered by tiny particles – in order to study a ring of dust orbiting the very young star HR4796. With previous instruments, only the edges of this dust ring (which may be the debris remaining from planet formation) could be seen. GPI can follow the entire circumference of the ring. The images were released today at the 223rd meeting of the American Astronomical Society in Washington D.C. Jan. 5-9.
“GPI’s performance requirements are extremely challenging,” explained LLNL engineer Lisa Poyneer, who developed the algorithms used to correct for atmospheric turbulence, and led the testing of the adaptive optics system in the laboratory and at the telescope. “As a result, the AO system features several original technologies that were designed specifically for exoplanet science. After years of development and testing, it is very rewarding to see the AO system operating so well and enabling these remarkable images.”
Imaging exoplanets is highly complementary to other exoplanet success stories like NASA’s Kepler mission. Kepler is extremely sensitive to small planets close to their parent star and focuses on mature stars – GPI detects infrared radiation from young Jupiter-like objects in wide orbits, the equivalent of the giant planets in our solar system not long after their formation.
“GPI represents a critical step in the road toward understanding how planetary systems form and develop,” said Dmitry Savransky, an LLNL postdoc who worked on the integration and testing of GPI before moving to a position at Cornell. “While broad survey missions, such as Kepler, have revealed the variety of planets that exist in our galaxy, GPI will allow us to study a few dozen planets in exquisite detail.”