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2035
In development
Heliocentric
Astrophysics observatory
Gravitational waves stretch and squeeze spacetime, affecting all bodies in space including the Sun and spacecraft. They have been detected by ground-based observatories in recent years – thanks to the LIGO-Virgo-KAGRA Collaboration – but these facilities are limited in size and sensitivity, meaning that they are only able to detect gravitational waves in the frequency range from a few tens to several thousands of hertz, which corresponds to signals from stellar-mass compact objects such as black holes and neutron stars. To detect millihertz-frequency gravitational waves, an observatory must span millions of kilometres – something that can only be achieved in space. LISA will be able to scour the entire Universe in its hunt for these elusive waves, across a large range of frequencies corresponding to timescales from seconds to several hours. This will enable scientists to study compact stars in our galaxy and massive black holes millions of times more massive than our Sun.
One of the unique phenomena that LISA is expected to observe are extreme mass ratio inspirals. These events involve a small compact object, such as a black hole or neutron star, spiralling into a massive black hole at the centre of a galaxy.
Animation illustrating the inspiral of a 10 solar-mass black hole into a spinning supermassive black hole with a mass of one million solar masses. As the smaller black hole spirals inward, it generates gravitational waves, which LISA can detect. Credit: ESA/Lorenzo Speri; background image: ESA/Euclid/Euclid Consortium/NASA, image processing by J.-C. Cuillandre, E. Bertin, G. Anselmi
We want to uncover the secrets of the Universe by addressing key questions about gravitational waves:
Study compact binary star systems:
How do compact binary stars form and evolve, and what can they tell us about the structure of the Milky Way?
Investigate massive black hole formation:
How do massive black holes form, grow, and merge across cosmic time?
Analyse extreme mass-ratio inspirals:
What can extreme and intermediate mass-ratio inspirals reveal about the properties and environments of black holes at the centre of galaxies?
Explore fundamental physics with gravitational waves:
How can gravitational waves help us explore the nature of gravity, the expansion of the Universe, and unexpected astrophysical sources?
LISA will use laser interferometry to detect and measure gravitational waves in space. Three spacecraft, arranged in a triangular formation millions of kilometres apart, will host free floating cubes and will send laser beams between them to detect tiny ripples in spacetime caused by cosmic events like merging black holes. By measuring these distortions with extreme precision, LISA will explore the nature of gravity, black holes, and the early Universe.
Animation showing the stretching and squeezing effect of gravitational waves increased by several orders of magnitude on both the orbits and the LISA satellites. Credit: Stefan Strub (https://zenodo.org/records/6761175).
Illustration showing how LISA will measure gravitational waves. Credit: ESA/ATG Medialab
LISA builds on the LISA Pathfinder mission, constructed to prove that the technology needed to measure gravitational waves, something never done before, would function in space. The mission was a great success, surpassing the team's initial expectations, setting the stage for LISA.
There is an exciting and unique opportunity for LISA to collaborate with ESA's forthcoming X-ray observatory NewAthena. Coordinated observations will enable 'multi-messenger' astronomy, providing further breakthroughs in modern astrophysics.
LISA is an ESA-led mission with contributions from NASA who will provide key technologies including the telescope and laser systems, and will support the mission operations. The LISA Consortium, comprising European and US institutions, is responsible for instrument development and data analysis. Airbus is the prime contractor for building the spacecraft.
Sonification of a gravitational wave emitted by extreme mass ratio inspirals made from its time-frequency map. Credit: ESA/Lorenzo Speri.
Space-time is rippling, but we can’t hear it – until we tune into its hidden symphony. This sonification transforms a gravitational wave signal from an extreme mass ratio inspiral into sound. Originally far below the range of human hearing, the frequency of the wave has been shifted upwards to make it audible. The image shows a time-frequency map of the signal: each bright track reveals a different tone, carrying clues about the spiralling motion of a small object around a massive black hole. In listening, we begin to understand how gravity sings.
For many years, measuring gravitational waves in space felt like a distant dream. Pete Bender was the first to suggest the concept, sparking ideas and theories, without much progress in practice. Things moved closer to reality in 1993, when a mission proposal was submitted to ESA to detect gravitational waves from space. LISA Pathfinder was eventually launched in 2015 to test the necessary technology. Around the same time, the first gravitational waves were detected from the ground – an achievement that earned a Nobel Prize. With momentum building, and LISA Pathfinder proving the tech could work, an L-class mission proposal was submitted and LISA was adopted in 2024. After decades of ideas and preparation, LISA is being built. It is set to make Europe leaders in gravitational wave physics.
Explore a subset of the ESA Science Programme missions here. Additional mission pages are in progress.
The currently available mission pages are ESA's flagship missions launched from 2013 and to be launched (L-class), and the ones in development (M- and F-class).
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