 This is the ESOcast, cutting-edge science and life behind the scenes of ESO, the European Southern Observatory. Exploring the ultimate frontier with our host Dr. J, a.k.a. Dr. Joe Liske. Hello and welcome to this special episode of the ESOcast. Leading up to ESO's 50th anniversary in October 2012, we will showcase eight special features, portraying ESO's first 50 years of exploring the southern sky. Have you ever wondered about life in the universe? Inhabited planets orbiting distant stars? Well, astronomers have for centuries. After all, with so many galaxies and each with so many stars, how could the Earth be unique? In 1995, Swiss astronomers Michel Mayor and Didier Kélo were the first to discover an exoplanet orbiting a normal star. Since then, planet hunters have found many hundreds of alien worlds, large and small, hot and cold, and in a wide variety of orbits. Now we are on the brink of discovering Earth's twin sisters, and in the future, a planet with life. The holy grail of astrobiologists. The European Southern Observatory plays an important role in the search for exoplanets. Michel Mayor's team found hundreds of them from Cerro Le Silla, ESO's first Chilean foothold. Here's the corally spectrograph mounted on the Swiss-Leonard Euler telescope. It measures the tiny wobbles of stars caused by the gravity of orbiting planets. ESO's venerable 3.6-meter telescope is also hunting for exoplanets. The Harp spectrograph is the most accurate in the world. So far, it's discovered more than 150 planets. It's biggest trophy, a rich system containing at least five and maybe as many as seven alien worlds. But there are other ways to find exoplanets. In 2006, the 1.5-meter Danish telescope helped to discover a distant planet that is just five times more massive than the Earth. The trick? Gravitational microlensing. The planet and its parent star passed in front of a brighter star in the background, magnifying its image. And in some cases, you can even capture exoplanets on camera. In 2004, NACO, the adaptive optics camera on the very large telescope, took the first image ever of an exoplanet. The red dot in this image is a giant planet orbiting a brown dwarf star. In 2010, NACO went one step further. This star is 130 light-years away from Earth. It is younger and brighter than the Sun, and four planets circle around it in wide orbits. NACO's eagle-eyed vision made it possible to measure the light of planet C, a gas giant ten times more massive than Jupiter. Despite the glare of the parent star, the feeble light of the planet could be stretched out into a spectrum revealing details about the atmosphere. Today, many exoplanets are discovered when they transit across their parent stars. If we happen to see the planet's orbit edge on, it will pass in front of its star every cycle. Thus, tiny, regular brightness dips in the light of a star betray the existence of an orbiting planet. The Charlie's Telescope at La Silla will help search for these elusive transits. Meanwhile, the very large telescope has studied a transiting planet in exquisite detail. Meet GJ-1214B, a super-Earth 2.6 times larger than our home planet. During transits, the planet's atmosphere partly absorbs the light of the parent star. ESO's sensitive 4-spectrograph revealed that GJ-1214B might well be a hot and steamy sauna world. Gas giants and sauna worlds are inhospitable to life, but the hunt is not over yet. Soon, the new Sphere instrument will be installed at the VLT. Sphere will be able to spot faint planets in the glare of their host stars. In 2016, the espresso spectrograph will arrive at the VLT and greatly surpass the current Harps instrument. And ESO's extremely large telescope, once completed, may well find evidence for alien biospheres. On Earth, life is abundant. Northern Chile offers its share of condors, vicuñas, viscachas and giant cacti. Even the arid soil of the Atacama Desert teems with hardly microbes. We've found the building blocks of life in interstellar space. We've learned that planets are abundant. Billions of years ago, comets brought water and organic molecules to Earth. Wouldn't we expect the same thing to happen elsewhere? It's the biggest question ever. And the answer is almost within reach.