The European Space Agency Will Launch Laser-Bots to Study Ripples in Spacetime

A trio of laser-shooting satellites built to directly detect gravitational waves in deep space has been officially greenlit by the European Space Agency (ESA), according to a Tuesday announcement.

Called the Laser Interferometer Space Antenna (LISA), the constellation is projected to launch around 2034, which puts it on track to become the first space-based gravitational wave observatory in history.

Gravitational waves are ripples in spacetime created by certain kinds of disruptions, like the collision of black holes or the explosions of massive stars. They have been described as a means to figuratively "hear" the universe, just as light allows us to see cosmic phenomenon.

Much like the Earth-based Laser Interferometer Gravitational-Wave Observatory (LIGO), which announced the first direct detection of a gravitational wave in history in 2016, LISA will create an optical tripwire over vast distances in order to capture the subtle distortion of passing waves. The constellation will trail behind Earth as it orbits the Sun, at a mean distance of 31 million miles (50 million kilometers).

Image: Nico 0692/ESA

But where LIGO's arms are 2.5 miles (four kilometers) long, the three LISA spacecraft will be separated by a whopping 2.5 million kilometers (1.6 million miles) in a triangular formation, making it thousands of times more sensitive than LIGO.

This colossal scale is the great advantage of space-based gravitational wave observatories, which is why scientists have been pursuing these missions for decades. LISA was first proposed by ESA in the early 1990s, with NASA becoming an official partner in 1997, only to withdraw over a decade later, in 2011, citing budget limitations. The mission is now officially led by ESA, with NASA still hashing out its role and future contributions to the mission, which will depend on the American agency's own priorities.

The LISA Pathfinder mission, launched by ESA in December 2015, has already successfully road-tested some of the technologies that LISA will rely on for its detection. Now that LISA has been officially selected as a priority for the European space community, this space triangle of cosmic-ripple-detecting laser bots is that much closer to reality.

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