Chile earthquake and telescopes
The latest earthquake to hit Chile was located near Concepcion, just south of Santiago.
Sadly, early reports of fatalities are emerging. In addition to the unfortunate loss of lives and livelihoods, Chile has to worry about something that is of interest to the astronomical community: telescopes.
Given that Chile is one of the most seismically active in the world, it’s a wonder that the country hosts some of the most powerful telescopes on the planet. These include the European Southern Observatory’s Very Large Telescope (VLT) in Paranal, Chile. It’s high in the Chilean Andes, about 1600 kilometres from Santiago. Even the planned 42-metre European Extremely Large Telescope is most likely going to be built in Chile.
Eyewitness reports on the BBC say that the Concepcion quake was felt as far away as Pergamino, Argentina, 200 kilometres north of Buenos Aires and about 1800 kilometres from quake’s epicentre.
So, most likely, ESO’s facilities on Mount Paranal would have felt the quake.
The four 8.2-metre telescopes that make up the VLT are well equipped to deal with earthquakes. Here’s a paragraph from The Edge of Physics that describes how the primary mirrors of the VLT are protected when the Earth shakes:
- The primary mirror is 18 centimeters thick. Because of its weight, the mirror’s precise shape can warp when it is tilted, so 150 actuators, upon which the mirror rests, continually push and pull at least once a minute to ensure that the optimal curvature is maintained. More impressive than the actuators are the clamps around the edges of the mirror, which can, at a moment’s notice, lift the entire mirror, all 23 tons of it, off the actuators and secure it to the telescope’s support structure in case of an earthquake (moderate quakes, of less than 7.75 Richter, are not uncommon here, thanks to the ongoing collision of the Nazca and South American plates). The entire telescope is designed to swing during an earthquake, and securing the primary mirror prevents it from rattling against the metal tubes that surround it.
To see the 8.2-metre mirror and the actuators, click here for pictures (the mirror is the seventh in the slideshow).