It has been twenty years since the first confirmed discovery of an exoplanet - a planet orbiting a major star. But in 2014 alone, astronomers discovered an incredible 800 alien planets. Today scientists are focusing less on new exoplanet discoveries, opting instead to focus on what they are made of.
Earth is called a rocky planet, as opposed to planets that are made up of ice or gas. Scientists already know there are many exoplanets that are Earth-like, but what they don't know is if they contain the same chemical compositions and locations to support life. However, in new investigations researchers are using a HARPS-North, an instrument that can measure the masses of Earth-sized planets, to better estimate the chemical composition of exoplanets much akin to Earth.
But what scientists have discovered is that not all planets that are close to the size of Earth are very Earth-like at all. Some have very low densities compared to the Earth, but researchers have also found that if an exoplanet has the right density for rockiness, they also seem to have the same chemical composition as the Earth.
For scientists, finding the exoplanets that are rocky with similar densities to Earth could be their best bet for finding complex life on other planets, as well.
Another study suggests that the oldest super-Earths may be the most likely candidates to contain life. Laura Schaefer, of the Harvard-Smithsonian Center for Astrophysics, used computer simulations to estimate how water would form and behave on a plant 1.5 times larger than the Earth. She estimates that it might take 5.5 billion years to create complex life -- about a billion years longer than it took on Earth.
Debra Fischer, a Yale professor commenting on the findings reminded everyone that twenty years ago astronomers worried there might not be life outside our solar system.
"Here's the universe twinkling with the lights of other stars, and we had to think that maybe there weren't other planets orbiting around them." Fischer says. "But now we know that almost every star has its own planetary system - a remarkable shift for just two decades of work."
"And now we're talking about a planet when we can barely see the star and yet we're able to talk about the mass of the planet, we can do a diagram slicing through to see the core of the planet, we can have a serious scientific dialogue. This is incredibly moving."
The next question scientists must answer is where the habitable planets are, if they do indeed contain life. Then, according to Fischer, we must figure out how to get there. Though the answer seems a far off future, Fischer is hopeful and says that with the progression of research, that could be in as little as 50 years.
