LISA is a go. After decades of development and delays, the European Space Agency has given the Laser Interferometer Space Antenna mission, designed to study gravitational waves in space, the official green light. The triplet spacecraft are now slated for launch in 2034.
“I think there’s a mixture of super-excitement and ‘at last’,” says Mark McCaughrean, ESA’s senior advisor for science & exploration. “We’re finally over the starting line – it’s great.”
LISA will be made up of three identical satellites orbiting the sun in a triangle formation, each 2.5 million kilometres from the next. The sides of the triangle will be powerful lasers bounced to and fro between the spacecraft.
As large objects like black holes move through space they cause gravitational waves, ripples which stretch and squeeze space-time. The LISA satellites will detect how these waves warp space via tiny changes in the distance the laser beams travel.
In order to detect these miniscule changes, on scales less than a trillionth of a metre, LISA will have to shrug off cosmic rays and the particles and light from the sun. The LISA Pathfinder mission, a solo probe launched in December 2015, proved that this sensitivity was possible and galvanized researchers working to realise the full LISA mission.
With such high sensitivity, one challenge will be sifting through colossal amounts of data to find the signals with the most scientific promise.
“That’s the amazing thing – we can hear everything in the universe with gravitational waves,” says McCaughrean. The prime targets for LISA observation, he says, will be merging supermassive black holes up to millions of times bigger than the black holes mergers detected in recent years by LIGO, the premier Earth-based gravitational wave observatory.
Since supermassive black holes spiral towards each other and merge much more slowly than smaller ones, LISA will be able to provide prior warning of any upcoming mergers to astronomers, offering a chance to observe them with other telescopes as well
“We’ll be able to see signals for months, so we’ll have time to point all these other telescopes at that point in the sky to see if there’s any other signals coming from that area when the merger happens,” says McCaughrean. This could yield further insight into how black holes and their collisions work.
At the same committee meeting that gave LISA the go-ahead, ESA also moved ahead with a new exoplanet-finding observatory, PLATO. Construction will soon begin on the spacecraft, which will survey bright stars across a large area of the sky, looking for tell-tale dips in light as an orbiting planet passes in front of its star.