The Sky at Night: The Very Large Telescope (BBC Four Monday 11 September 2023)

The Sky at Night: The Very Large Telescope airs Monday 11 September 2023 on BBC Four.

What is this episode about

Some of the most important discoveries in the history of astronomy, including some that led to Nobel Prizes and fundamental shifts in our understanding of the cosmos, were made possible by the VLT. The Sky at Night crew visits one of the most cutting-edge ground-based optical astronomy facilities in the world in the heart of Chile’s Atacama Desert.

The Paranal Observatory, where the Very Large Telescope (VLT) is housed, is situated in the Atacama Desert, the driest place on Earth (aside from the North and South Poles), and thus an ideal location for an observatory due to the low humidity levels there.

The VLT consists of four main telescopes that can be used separately or in tandem to maximise the observing power. The enormous 8.2 metre mirrors at the heart of each telescope are optimised to collect as much light as possible, allowing for observations on Earth that are nearly as sharp as those made in space.

Maggie gets to know some of the researchers, engineers, and astronomers at this remarkable facility. The first person she encounters on her journey is Maxime Boccas, the company’s head of maintenance, support, and engineering. He is in charge of the biannual mirror cleaning that nobody else does but him. Maxime elucidates the extraordinary processes involved in the care and upkeep of such massive yet fragile mirrors, including the vaporisation of aluminium particles to produce flawlessly reflective surfaces.

Dr. Joe Anderson, an astronomer, is one of the people putting the incredible telescopes to use in their research. Joe is one of many researchers who use the VLT’s array of specialised instruments to analyse light from space and gain new insights into the cosmos. Joe explains that the VLT is the most advanced visible-light astronomical observatory in the world because of its enormous mirrors and variety of instruments, which allow astronomers to get readings across a broad spectrum, leading to many new discoveries about exoplanets, black holes, and gamma-ray bursts.

Maggie then meets Vanessa Peidro, the head of logistics, who oversees the upkeep of the VLT’s buildings, vehicles, and the food, water, and other facilities that serve the 150-160 people who are usually present at the site at any given time.

Francoise Delplancke-Stroebele, a physicist, and Frederic Gonte, a colleague of hers, are the next people Maggie meets. By combining light waves in a technique called interferometry, they explain how the four massive telescopes at the VLT work together as a whole, and they are leading the VLT’s next upgrade, Gravity+. Dr. Abigail Frost, an astronomer, uses interferometry to shed light on the discovery of a rare ‘vampire star’ in the sky.

The VLT is still a top-tier facility for groundbreaking research, but it will soon be upgraded to a much more potent facility. Construction has begun on the Extremely Large Telescope, or ELT. Maggie visits the site of what, when finished in five years, will be the largest optical telescope ever built. The ELT, which sits atop a mountain and is as large as a cathedral, is undoubtedly an impressive architectural achievement.

When can we see the episode

The Sky at Night: The Very Large Telescope airs Monday 11 September 2023 at 9:30pm on BBC Four

Featured Image Credit: BBC Four