Scientists discover Earth-like planet orbiting star closest to our sun in 'habitable zone'

Astronomers from the European Southern Observatory announced a breakthrough discovery in the search for Earth-like worlds outside our solar system on Wednesday as they revealed researchers have found a comparably sized exoplanet orbiting the star closest to ours.

The planet, dubbed Proxima b because it orbits Proxima Centauri, is believed to be a rocky planet that's slightly more massive than Earth. Researchers also discovered that it orbits its sun in what's known as the "Habitable zone" -- a term used to refer to an orbital distance that creates conditions believed to be required to foster life -- mostly notably, liquid water.

The discovery is especially impressive because Proxima Centauri is our closest neighbor in galactic terms. The star is a mere four lightyears away from our solar system, which means that an object traveling at the speed of light would take only four years to reach it.

Check out images of the planet and its star:

This makes the exoplanet the closest outside our solar system that could potentially sustain human life.

But that distance -- about 25 trillion miles -- is still pretty daunting using current flight technology. Even the most ambitious estimates suggest it would take a spacecraft nearly 18,000 years to reach the planet. Others suggest it could take as long as 165,000 years.

But that could be sped up significantly thanks to the efforts of Stephen Hawking, who launched a $100 million project earlier this year called Breakthrough Starshot, designed exclusively to help humans explore Proxima Centauri and other close solar systems using what he calls a nanocraft.

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"With light beams, light sails and the lightest spacecraft ever built, we can launch a mission to Alpha Centauri within a generation," Hawking said during the release in April. "Today, we commit to this next great leap into the cosmos. Because we are human, and our nature is to fly."

Neither the star nor exoplanet Proxima b are visible with the naked eye, but both are located in the constellation Centaurus, which is visible from the tropics and all of the Southern hemisphere.

Exoplanet detection is a relatively new field of study. The first planets outside of our solar system were discovered in the last three decades, but the field has exploded in recent years thanks in large to the Kepler space telescope. Kepler has discovered more than 3,000 exoplanets since 2009, including many that are roughly the size of Earth.

The first Earth-sized exoplanet discovery in the so-called "Habitable zone" came in 2014, with the announcement of Kepler-186f.