Construction of the European Extremely Large Telescope in Chile was approved on Thursday, December 4. When it's completed in 2024, the $1.3 billion project will be the world's largest telescope. The instrument will help astronomers find planets in other solar systems — and perhaps even signatures of extraterrestrial life.

Why scientists are building a giant telescope

On Wednesday, the European Southern Observatory (ESO) announced approval of the European Extremely Large Telescope — a truly enormous telescope that will be constructed in Chile's Atacama Desert and completed by 2024.

The ESO — an astronomy organization made up of 15 nations in Europe and South America — first proposed the telescope in 2006. In 2012, the organization approved the $1.3 billion project under the condition that 90 percent of the funding be committed by the countries involved, and during a meeting Wednesday, the ESO Council announced the goal had been met, and authorized construction to begin.

Once it's finished, the telescope will be the world's largest, with a 128-foot wide composite mirror that's about four times wider than any existing telescope. These mirrors, which concentrate light into the lens, will be able to collect roughly 100 million times more light than the human eye. And the telescope's location atop a mountain in the Chilean desert means that it'll be able to look through relatively thin, dry air, providing better images of the sky.

The telescope's primary goal will be to search for planets in other solar systems — especially smaller, Earth-sized planets that could be home to life. So far, scientists have found more than a thousand exoplanets, but the vast majority are larger gas giants that are easier to spot, but less likely to contain life.

"We need big telescopes like this because Earth-like planets are smaller, and have relatively thin atmospheres — so we need to take in a lot of light to analyze them and search for potential signatures of life," says Lisa Kaltenegger, Director of Cornell's new Institute for Pale Blue Dots, which aims to look for life on other planets.

Scientists will also use the telescope to study the formation of distant star systems — providing clues to how our solar system may have formed 4.6 billion years ago — as well as even more distant galaxies, observing how they evolve over time.

To get an idea of just how enormous this telescope will be, take a look a this scaled diagram of existing telescopes and other ones that will be constructed in the future: