A green laser beam pierces through the night sky and moves across until it reaches Crux, often called the Southern Cross. This part of the world doesn’t have a fixed point in space like Polaris, the North Star. Crux one of the best ways to navigate, using the unique position of its brightest four stars. It’s not an obvious constellation. It has a subtle elegance like a diamond-shaped kite in the sky.

A pair of guides from San Pedro de Atacama is giving a small group of sightseers a tour of the stars. There are several astronomy tours in town and they all promise an unforgettable stargazing experience. The Atacama Desert in Chile is acclaimed as one of the darkest places in the world.

It’s dark, but it’s not pitch black.

San Pedro de Atacama is about three miles north of where we’re standing, and the glow of the town lights obscures the skyline behind it. The eastern skyline is dark enough that a lightning storm behind the Andes Mountains is visible. The streetlights in town are dim, amber and diffused by a frosted casting, but a lowly lit town like this can still cast sky glow.

Even in the darkest desert on Earth, you can’t escape the illumination that comes with humankind. The guides point out constellations and stars like Orion, Sirius and Alpha Centauri, but there’s no sign of the Milky Way. The hour-long tour ends at about 10 p.m., and it feels lackluster.

“How can they have a tour that ends at 10 p.m.?” photographer Nicholas Buer says the next night. “The best part doesn’t even start until now.” We’ve commissioned him to take photos of the night sky in Atacama. It’s about 1 a.m., which is around the time he says the Milky Way is high enough in the sky to see clearly. It’s summer in the southern hemisphere, and it’s impossible to see the nucleus of our galaxy, but Buer says there will plenty to see that isn’t visible in the northern hemisphere like the Magellanic Clouds. We’re also in for a spectacular light show. It’s December and the Geminid meteor shower is peaking.

In the outskirts of Laguna Tebinquinche, Buer wants to capture a reflection of the stars in a small pond. It’s about a 20-mile drive from San Pedro de Atacama. There are small dots of light in the distance from copper and lithium mines. The camera has been snapping photos for about an hour when Buer notices his tripod sinking into the crusty, dried mud surrounding the marsh, about a centimeter so far.

“We’ve got about eight seconds,” he says. It’ll have to do.

We pack up and drive out to the other locations on our list. It’s pitch black without another car in sight. The route is paved, but we’re not on the main road. Our shoot is timed around the new moon, so we’re guided only by our truck’s high beams. Going on ­­our memory of the road at dusk, we find a lone Algarrobo tree in the dark. It takes a minute for our eyes to adjust to the dark after the headlights go off.

We look up and there it is: the Milky Way high in the sky, drifting in a bright web of stars that begin at the horizon. To the right of the southern arm of our galaxy, the Magellanic Clouds linger like two puffs of white smoke. The satellite galaxies will circle in the sky all night.

The Atacama Desert’s size is tough to measure, but it’s estimated to be between 600 to 700 miles from north to south. Cold, dry air equates to clear conditions, making it ideal for stargazing, with the naked eye or with telescopes. Because the average rainfall is less than half an inch a year, weather considerations revolve more around the extreme temperature swings than possible rainstorms.

The desert’s red, rocky landscape has been compared to Mars. NASA and the European Space Agency have tested rovers on the terrain because of its similarities to the Red Planet.

At Valle de la Luna, rocky canyons and sand dunes flank the main road, which are surrounded by salt deposits of a dry lakebed that line the floor of the valley. Walking through it feels like a trek through its namesake, the moon. Only a 10-minute drive from San Pedro de Atacama, the nature sanctuary is famous for its sunset tours.

Researchers are drawn to the desert because it’s arid and isolated. The Atacama Large Millimeter/submillimeter Array (ALMA) is about 30 miles from San Pedro de Atacama. The observatory is home to 66 radio telescopes that study the sky in search for a clue about our origin. There’s a saying that the sun never sets on ALMA. Scientists from all over the world visit the facility to conduct research. Sunscreen and water are available throughout the ALMA Operations Support Facility. The elevation is about 9,500 feet, thus higher levels of radiation and risk of dehydration.

Dr. Rein Warmel, an astronomer with the European Southern Observatory’s (ESO), hopes to uncover the origins of the universe.

“What you’re trying to understand is how galaxies are formed, how stars are formed in these galaxies,“ he says. Warmel has access to the best tools on earth. He adds, “ALMA is particular in this millimeter, submillimeter area. There are loads of atoms and molecules emitting in the universe. We’re mapping this. We’re making pictures of those.”

The researchers at ALMA need clear skies for a different reason. Warmel says that radio telescopes are starting to pick up signals from modern devices like smartphones. “That’s the reason you try to build these things in protected areas. There’s not a lot of interference from mankind,” he says.

San Pedro de Atacama has a population of about 2,500 people. Although it’s a tourist town, it’s not an easy place to reach. It’s a 90-minute drive away from the nearest airport in Calama. Beyond the tarmac at El Loa airport, there’s only rust-colored earth, dark mountain ranges and puffs of dust kicked up by trucks. This alien quality hangs over everything in Atacama, a desolate gateway to the most famous night sky on earth. Absolute darkness isn’t easy to find, but there’s a better chance you’ll find it here than just about anywhere else.