Meet the telescope behind the Pac-Man photos

According to the memes circling around this weekend, Mecha Pac-Man has a fondness for lunar cheese and starlight, gaping wide to gobble them both. In reality, the telescope behind the Pac-Man photograph is Auxiliary Telescope 2, an essential component of the most productive ground-based telescope on the planet.

Auxiliary Telescope 2 has been making the rounds on social media due to its resemblance to the classic arcade hero Pac-Man with the perfectly-placed silver bauble. The accompanying comments threads spawned dystopian fiction and evoked fears of the Shai-Hulud relocating from Dune to Earth. But it's a real telescope run by the European Southern Observatory (ESO) at the Paranal Observatory in the Atacama Desert in Chile. The creatively-named Very Large Telescope is an array of four 8.2 meter main telescopes, and four 1.8 meter auxiliary telescopes.

Meet the telescope behind the Pac-Man photos

You've seen the surroundings before: remember James Bond's repressed emotional angst before bursting out in vengeance during Quantum of Solace? That took place at the observatory's hotel, where visiting researchers stay. Something about subterranean architecture, skylights, and views of the distant ocean elicits high-octane explosion-riddled climaxes.

Getting back to astronomy, the four main telescopes are named after astronomical objects in a local native dialect: Antu, Kueyen, Melipal, and Yepun. The four auxiliary telescopes, including the newly-beloved Mecha Pac-Man, are only numbered. That's okay, VLT Auxiliary Telescope 2, we still love you. The telescopes work together to form a giant interferometer. The light from each telescope is combined to form an image that is 25 times more detailed than what could be produced by any of the telescopes working in isolation.

Meet the telescope behind the Pac-Man photos

In order to combine the beams, a complex system of mirrors bounces the light through underground tunnels. The path each beam takes must exactly match the distance travelled by the other beams. Path lengths may be up to several hundred meters travelled with less than a micron of variation between beams! Or more poetically, that's bouncing beams of light several times the length of a football field, and having them all travel the same distance plus or minus the width of a bacteria.

Continuing our theme of adorable animals hanging around observatories, of course VTL has a resident fox.

The end result of scooting telescopes and juggling light beams is a telescope array with combined angular resolution of 1 milliarc second. The poetic analogy listed on every VLC factsheet is that that kind of resolution is enough to distinguish between each headlight on a moonbuggy. But stop and think about that: this telescope can spot the difference between light sources two meters apart, from 385,000 kilometres away. That is seriously impressive.

The main telescopes are housed in thermally-controlled buildings at fixed locations. As the telescopes rotate to track celestial objects, the building rotate with them to minimize interference from observing conditions. After all, you can't let a fancy telescope like this get mucked up by air turbulence in the telescope tube, wind, or a change in temperature!

Atmospheric jiggling is downright irritating when working with telescopes. As light passes through the atmosphere, it gets knocked, bent, and otherwise distracted by air. If only we knew exactly what happened to the light, sighed astronomers one day, we could process the data to exactly reverse it and get our perfect light back... Just like that, adaptive optics were born! Okay, fine, not really, but we really did start shooting powerful lasers out of telescopes to create Laser Guide Stars.

Meet the telescope behind the Pac-Man photos

Deathstar laser guide-star compensating for atmospheric instability.

The familiar orange glow of the Laser Guide Star is the same colour as sodium street lamps for good reason: it energizes sodium atoms in the upper atmosphere. How did sodium get into the upper atmosphere? It's probably leftover from meteorites burning up entering the atmosphere when one of those space-rocks I keep talking about get a little too close. The laser excites the sodium to create a bright artificial star about 90 kilometres up. That known light source is used to adjust deformable mirrors in real time, correcting for constant erratic motion of atmospheric gases. The correction is so good that it removes almost all atmospheric effects, allowing ground-based telescopes to compete with the clarity of images produced by space-telescopes like Hubble.

The auxiliary telescopes, including AT2 (aka "Pac-Man"), are in self-contained buildings that slide along rails to any of 30 observing locations. By shuffling the auxiliaries' locations, the array size can be adjusted to trade between field of view and angular resolution. The boxy base is the transporter section containing all the electronics cabinets, liquid cooling systems, air-conditioning units, power supplies, and everything else necessary to keep the telescopes happy. This entire section is mechanically isolated from the telescope during observations to prevent any stray vibrations from compromising data collection.

Meet the telescope behind the Pac-Man photos

Auxiliary Telescope 3 is ready to slide along the tracks in preparation for a new observing project.

The segmented domed sections that give the units their distinctive appearance hide the telescope. The pair of triple-segments enclosures snap shut to protect the delicate instrument from desert dust during the day, and slide open to allow unhindered observing at night.

Meet the telescope behind the Pac-Man photos

The auxiliary telescope is spread open for observations during this 15-second exposure. The skies above the Atacama Desert are so clear that even on a moonless night, the glow of the Milky Way is strong enough to cast shadows!

The VLT is a powerhouse of an observatory, producing on average a peer-reviewed research paper every single day. The observatory took the first photograph of an exoplanet, tracked stars moving around or galaxy's black hole, and caught the aftermath of the farthest-ever gamma-ray burst.

Top photograph by Eric Lagadec, who immediately recognized the classic shape. VTL resident-fox by Vivien Bonvin. All other photographs credit to the European Southern Observatory. Their galleries have excellent photographs, including this one of Mecha Pac-Man's greatest nemesis, stompy-child.