The only thought more terrifying than being alone in the universe? Not being alone. For many researchers and avid star watchers, however, the latter is gaining ground in the scientific community.

With the advent of high-powered telescopes and spectrographic technology, scientists are now able to observe planets that reside light years away from Earth’s solar system. Several of these planets, called exoplanets, orbit stars, making them viable candidates for potential habitation, similar to what is seen on Earth. Although by no means conclusive, research projects have identified well over 50 of these celestial bodies, bringing the goal of finding a planet similar to Earth all the more closer.

The identification of these exoplanets is difficult, deviating far from a simple pointing of the telescope. The two most common methods make use of sensitive measuring techniques, according to Bruce Fegley, a Professor of Earth and Planetary Sciences at Washington University in St. Louis. Most researchers utilize sensitive spectrographs to detect shadows on the surfaces of distant stars.

“The planet crosses in front of the star and partially blocks some of the starlight that we see from Earth,” Fegley said. “The decrease in starlight is very small, much less than one percent, but this is easily detectable by the specially designed telescopes on the spacecraft.”

Another, more reliable method is called the radial velocity method. This searches for minute wobbles in the speed of a star’s orbit, indicating the presence and effect of an orbiting exoplanet.

“A star with a planet will move in its own small orbit in response to the planet’s gravity,” Fegley said. “This leads to variations in the speed with which the star moves toward or away from Earth.”

These wobbles and shadows indicate the presence and relative mass of any exoplanets, but that’s it. Without further research into the composition of the planet, it remains impossible to accurately determine if planets are capable of sustaining life, according to Fegley’s information.

“[Composition could be detected] if one could measure the surface temperature, pressure, and atmospheric composition. This is possible only for planets in our solar system using spectroscopy from telescopes on Earth,” Fegley said.

Simply orbiting a star, however, is not enough to ensure that a planet will be able to support carbon-based life forms. Instead, planets must occupy a space in the so-called “Goldilocks” zone, a “not too cold, not too hot” orbit that allows the presence of liquid water on the planet’s surface.

“Earth is in the zone, but neither Mars nor Venus is in it,” Fegley said. “If they were, Mars would be warmer with a thicker atmosphere, and Venus would be cooler with a thinner atmosphere.”

Currently, the most viable Goldilocks candidate resides 36 light years from here within the Vela constellation. Given the easily-remembered moniker of HD 85512b, scientists believe that this exoplanet could be viable, provided that is has the proper cloud cover and a rocky surface. A friendly visit, however, is out of the question.

“It may be possible to launch a robotic probe,” Fegley said, “but the time required to get from here to there is so long that at least thousands of years would be required.”