Unveiling LISA - a constellation of three space satellites positioned 2.5 million kilometers apart, designed to identify gravitational waves in the universe.

In a groundbreaking development, the European Space Agency (ESA) has given the go-ahead for an international team of scientists to begin building the Laser Interferometer Space Antenna (LISA) in January 2024. This space-based constellation of three satellites will revolutionise our understanding of the Universe, as it sets out to study ripples in spacetime, known as gravitational waves.

LISA will be the largest gravitational wave detector ever built, and it will be in space. This is a significant step, as the first detection of gravitational waves, GW150914, was made in September 2015 by the twin detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO). However, LISA will delve into a low-frequency region unreachable by ground-based observatories, opening up a new window to the cosmos.

The Laser Interferometer Space Antenna (LISA) will consist of three identical satellites in a triangle formation, separated by 2.5 million km (1.5 million miles). These satellites will use lasers to measure the distance between each other and monitor changes in the light's arrival time for gravitational wave detection.

LISA will test the technology demonstrated by the LISA Pathfinder test mission, launched in 2015. It will also test Einstein's theory of gravity in the most extreme regime ever probed, comparing gravitational waves from merging massive black holes with high-precision predictions, providing the most stringent test of general relativity to date.

One of the key objectives of LISA is to study stellar-mass compact objects falling into massive black holes, known as extreme mass ratio inspirals. It will also observe the collision of massive black holes, from the current-day Universe back to when the Universe was 0.18 billion years old. LISA will yield a unique census of isolated and relatively unperturbed massive black holes.

Moreover, LISA will verify the no-hair theorem, stating that black holes can be completely described by their mass, charge, and angular momentum. This could provide valuable insights into the nature of black holes and the fundamental laws of physics.

The increased sensitivity of O4, the latest 18-month observing run of the LIGO-Virgo-KAGRA collaboration, entered in May 2023, has already made gravitational wave detection more frequent. With LISA, this frequency is expected to increase significantly. In fact, LISA is anticipated to result in a gravitational wave detection every two or three days, compared to every week as seen previously.

In essence, if we want to set our sights on grander targets and detect gravitational waves from the Universe's birth, we must venture to a new location - space. And with LISA, we are one step closer to that goal. Construction is set to begin in the 2030s, with the promise of unlocking new secrets about the Universe and expanding our horizons.

Unveiling LISA - a constellation of three space satellites positioned 2.5 million kilometers apart, designed to identify gravitational waves in the universe.