APOD: ELT and the Milky Way (2024 Mar 16)

[APOD Robot]

ELT and the Milky Way

Explanation: The southern winter Milky Way sprawls across this night skyscape. Looking due south, the webcam view was recorded near local midnight on March 11 in dry, dark skies over the central Chilean Atacama desert. Seen below the graceful arc of diffuse starlight are satellite galaxies of the mighty Milky Way, also known as the Large and Small Magellanic clouds. In the foreground is the site of the European Southern Observatory's 40-metre-class Extremely Large Telescope (ELT). Under construction at the 3000 metre summit of Cerro Armazones, the ELT is on track to become planet Earth's biggest Eye on the Sky.

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[rstevenson]

“The southern winter Milky Way…”? On March 11 it was still late winter here in Nova Scotia, so I suspect it was still late summer in Chile.

Rob

[johnnydeep]

The ELT (Extremely Large Telescope) has its "first light" planned for 2028. I hope it can remain on track! A 39 meter primary mirror is quite remarkable. How will it compare to Hubble?

(And wasn't there going to be a new "ludicrously large telescope" on one of the Hawaiian islands, whose construction was delayed - if not permanently prevented - by local peoples' sacred site desecration concerns?)

M1, the ELT’s primary mirror, is the centrepiece of the revolutionary astronomy machine currently under construction in Chile's Atacama Desert. It is the surface that will gather light from cosmic objects, opening up new discovery spaces — from exoplanets close to their stars, to black holes, to the building blocks of galaxies — both in the local Universe and billions of light years away.

The M1 is, without a doubt, one of the most impressive and challenging aspects of the entire ELT project. Too large to be made from a single piece of glass, the 39-metre-diameter mirror will consist of 798 segments, each about 5 centimetres thick, measuring close to 1.5 metres across and weighing 250 kg, including its support. Since the segments have to work together as a single mirror, they require specific infrastructure and control schemes. This is extremely challenging, as the full structure will be moving constantly during an observation and will be affected by wind and thermal changes. To achieve the required scientific performance, the mirror needs to be maintained in position and in shape to an accuracy of tens of nanometres — 10000 times thinner than a human hair — across its entire 39-metre diameter!