From the Leviathan to the Behemoth

by Nicholas Mee on September 19, 2017

The Leviathan

The Rosse Telescope c. 1880, photograph Robert French.

William Parsons, the 3rd Earl of Rosse, built a monster telescope with a six-foot or 1.8 metre mirror weighing almost three tons at his home in Birr Castle in county Offaly, Ireland. Construction was completed in 1845. The Leviathan of Parsonstown, as it is known, remained in use until the end of the 19th century. When the 4th Earl died in 1908 the telescope fell into disrepair and was partially dismantled, but it was not until 1917 that a bigger telescope was built anywhere in the world.  In the late 1990s the Leviathan was renovated and a new mirror was installed.

Lord Rosse saw the heavens as they had never been seen before. He sketched these amazing sights and his drawings were widely circulated.

Left: Sketch of the Whirlpool galaxy made by Lord Rosse in 1845.  Right: Photograph by Nik Szymanek.

Camille Flammarion was a French astronomer and prolific author who wrote numerous books in the 19th century that brought science and astronomy to a wide readership. Flammarion’s book L’Astronomie populaire published in 1879 was very successful and influential and a huge best-seller, over 100,000 copies were printed. The book includes Lord Rosse’s sketch of the Whirlpool galaxy and it certainly is a stunning sight through a telescope. In Lord Rosse’s day it was thought to be a gaseous nebula within our own galaxy. We now know that it is a beautiful spiral galaxy that is being perturbed by the gravitational influence of a smaller galaxy in its vicinity.

In June 1889 Van Gogh painted The Starry Night. It represents the scene from the window of the Saint-Paul asylum in St. Rémy, Provence, in the south of France, where Van Gogh had admitted himself to seek refuge from his inner turmoil. But the striking feature of this wonderful painting is the sky. The cosmologist John Barrow makes a compelling case that the swirling patterns were inspired by Lord Rosse’s sketch of the Whirlpool galaxy which Van Gogh may have seen in Flammarion’s book or in contemporary newspapers following the great success of the book.

The Starry Night by Vincent Van Gogh (1889).

Fast Forward to Today

We are living through a golden age of astronomy. The advances in equipment in recent decades have been incredible. Telescopes have come a long way since the days of Lord Rosse. The European Southern Observatory (ESO), funded by 14 European nations, has constructed the most advanced optical observatory in the world, shown in the photograph below. The Very Large Telescope complex (VLT) sits at an altitude of 2,400 metres on a mountain top at Paranal in northern Chile. This site in the Atacama desert is in one of the driest regions on Earth. The incredibly low humidity and high altitude dramatically reduces the blurring effects of turbulence in the atmosphere and gives the observatory a view of the night sky with unparalleled clarity. The VLT consists of four main telescopes, each with an 8.2 metre diameter mirror, along with four 1.8 metre auxiliary telescopes.

The Very Large Telescope complex in the Chilean Andes. Credit: ESO.

In 1998, a competition was held to find appropriate names for the telescopes. The winner was a 17 year old school girl Jorssy Albanez Castilla from Chuquicamata near the city of Calama, close to Paranal, who proposed in her winning essay that the telescopes should be named after celestial objects in the local Mapuche language. Following her suggestion, the four main telescopes are Antu, Kueyen, Yepun and Melipal. In Mapuche, Antu means Sun, Kueyen means Moon, Yepun means Venus and Melipal means Southern Cross.

Adaptive Optics

Star-forming region in the Large Magellanic Cloud. Credit: ESO.

Even in the ideal setting of an Andean mountain top there is some atmospheric turbulence. To compensate for the atmospheric distortion of the starlight gathered by the huge telescope mirrors, the VLT uses adaptive optics. A laser is fired into the night sky and reflects from the upper atmosphere to produce an artificial point of light or guide star. This is continuously monitored through the telescope and a computer controlled feedback mechanism deforms the telescope mirrors to keep its image point-like. This mechanism compensates for fluctuations in the atmosphere and enables the telescopes to produce much sharper images than would otherwise be possible, rivaling a vastly more expensive space-based telescope. In addition the four main telescopes and the four auxiliary telescopes can be operated as an interferometer in which the light from the telescopes is channeled through underground tunnels and combined to form an ultra-sharp image of incredibly high resolution.

The results are spectacular, as can be seen from the image above which shows a star-forming region in the dwarf galaxy companion of the Milky Way known as the Large Magellanic Cloud. The nebulae in the image have been produced by intense stellar winds from extremely hot new-born stars.

The Behemoth

The European Southern Observatory has just started construction of what will be far and away the world’s largest telescope. This new behemoth is the Extremely Large Telescope (ELT). It is situated atop a mountain known as Cerro Armazones, twenty kilometres from the VLT complex, at an altitude of just over 3,000 metres. The composite mirror of the telescope will be constructed from 798 hexagonal segments, each 1.4 metres wide, making the full mirror a gargantuan 39 metres in diameter. This will enable the telescope to collect about 15 times as much light as any existing telescope and 470 times that of the Leviathan of Parsonstown. The telescope will incorporate an advanced adaptive optics system using several lasers and actuators that can distort the shape of the mirrors a thousand times each second.

An artistic impression of the ELT when complete. Credit: ESO.

Construction of the Extremely Large Telescope began in early 2017. The first observations are scheduled for 2024. Every advance in optical equipment has brought sensational discoveries about our place in the universe and the same will surely be true of the ELT. It will give astronomers the ability to search for the first generation of stars in the very early universe, it will enhance the search for Earth-like planets around distant stars and it will enable astronomers to probe the supermassive black hole at the centre of our galaxy, but, like its predecessors, it will also encounter the unknown.

Further Information

There is more information about ESO’s Extremely Large Telescope here:

You can see more of Nik Szymanek’s spectacular photographs here:

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