"We have detected gravitational waves, we did it," David Reitze, the executive director of the Laser Interferometer Gravitational Wave Observatory (LIGO) announced on Thursday.

In a highly-anticipated news conference in Washington, he confirmed that his team had detected the waves from two colliding black holes on September 14th, 2015.

"It took us months of careful checking, rechecking, looking at every available piece of data ... to make sure that what we saw ... was a gravitational wave," he added.

Reitze added that it was "exactly" what physicist Albert Einstein's theory predicted about the waves for two colliding black holes a century ago.

"The two black holes are indeed about 30 solar masses. They are about 1.3 billion light years away," he added.

Playing an audio clip of the short wave that the team was able to measure, LIGO researcher Gabriela González said the signal took a billion years to reach earth.

"The signal came from the Southern sky, in the rough direction of the Magellanic clouds (the satellite galaxies of the Milky Way)," adding that they couldn't tell with existing technology, exactly where the black holes merged.

"We will not only be able to see the universe but we will be listening to it too."

Historic announcement

Scientists who have been working on the project for decades attended the announcement. They included representatives from the California Institute of Technology (Caltech), the Massachusetts Institute of Technology (MIT) and the LIGO.

The LIGO team used a system of two identical detectors located in the US states of Louisiana and Washington to detect tiny vibrations from passing gravitational waves.

The detection of gravitational waves opens a new window on the universe and its most violent phenomena and offer exciting new avenues in astronomy, allowing measurements of faraway stars, galaxies and black holes.

Analysts said the discovery offers a way to study what the universe was like in its infancy, from shortly after the Big Bang.

Century-old theory

Einstein posited the existence of gravitational waves a century ago in his Theory of Relativity. He described how waves are produced by disturbances in the fabric of space and time when a massive object - such as a black hole or a neutron star - moves through space-time.

Einstein theorized that gravitational waves would appear like ripples in a pond that form when a stone is thrown in the water.

But until now, scientists have been able to find only indirect evidence of their existence because the waves are extremely hard to measure.

Tiny vibrations

Ripples emitted by a pair of orbiting black holes, for example, would stretch a one-million-kilometer (621,000-mile) ruler on Earth by less than the size of an atom.

Thursday's announcement confirmed rumors that have been circulating in the scientific community for months that the LIGO team may have indeed directly detected the illusive waves for the first time.

The confirmation has also been widely discussed on social media over the past few days.

Honors for best minds

The project's lead researchers are widely expected to win the Nobel Prize in Physics for their discovery.

Several other groups have attempted to observe gravitational waves but have only offered ambiguous clues or had their research later invalidated.

But in 1993, two Princeton scientists won the Nobel Prize in Physics in 1993 for discovering a new type of pulsar that offered indirect proof of the existence of gravitational waves.

mm/jil (AP, AFP, dpa, Reuters)