LISA – measuring gravitational waves

ESA’s mission, LISA, will capture and study ripples in the fabric of spacetime. These ripples, which we call gravitational waves, are emitted during some of the most powerful events in the Universe. An example of a system creating gravitational waves is a pair of black holes orbiting each other and heading for a collision. The acceleration of their huge masses shakes the fabric of space-time and creates ripples.

The LISA mission has three spacecraft that will fly in formation. Together they form an equilateral triangle connected by laser beams, trailing the Earth during its orbit around the Sun. Inside each spacecraft sit two free-floating golden cubes, also called test-masses.

When a gravitational wave passes by, the distances between objects contract and expand. By measuring the distance travelled by the laser beams between the test-masses in the different spacecraft, LISA will be able to detect gravitational waves and tell where they came from.

In the infographic, the sequence of triangles demonstrates the effect gravitational waves will have on the distance travelled by LISA’s laser beams. The effect is exaggerated to showcase the possible directions in which a gravitational wave would contract and expand the separations of the test masses.

[Image description: Infographic providing information on gravitational waves and how the LISA mission will measure them using laser beams and free-floating cubes. The image shows the three LISA spacecraft in orbit with the Earth and Sun visible. A zoomed in circle focuses on one of the spacecraft and the two golden cubes it contains. In the background an illustration of two colliding black holes is creating ripples in spacetime. Another box shows a sequence of triangles to demonstrate the effect gravitational waves will have on the distance travelled by LISA’s laser beams.]