Cosmic Explorer

a next generation gravitational wave detector


Cosmic Explorer is a next-generation observatory designed to greatly deepen and clarify humanity’s gravitational-wave view of the cosmos. It is the planned U.S. contribution to the global third-generation ground-based gravitational-wave detector network. The design concept for Cosmic Explorer features two sites, one 40 km in length and a second 20 km in length, each with an L-shaped observatory.

Cosmic Explorer together with other future detectors, including LISA and the Einstein Telescope, will be able to determine the nature of the densest matter in the universe; reveal the universe’s binary black hole and neutron star populations throughout cosmic time; provide an independent probe of the history of the expanding universe; explore warped spacetime with unprecedented fidelity; and expand our knowledge of how massive stars live, die, and create the matter we see today.

With its spectacular sensitivity, Cosmic Explorer will see gravitational-wave sources across the history of the universe. Sources that are barely detectable by Advanced LIGO, Advanced Virgo, and Kagra will be resolved with incredible precision. The explosion in the number of detected sources — up to millions per year — and the fidelity of observations will have wide-ranging impact in physics and astronomy. By peering deep into the gravitational-wave sky, Cosmic Explorer will present a unique opportunity for new and unexpected discoveries.

See the Horizon Study for more information on Cosmic Explorer science, design and technology.


Like the current generation of observatories, Cosmic Explorer features an L-shaped geometry and houses a single interferometer. Each Cosmic Explorer facility will have two 40 km (20 km for the second site) ultrahigh-vacuum beam tubes, roughly 1 m in diameter, built in an L-shape on the surface of flat and seismically quiet land in the United States. This conventional design leverages decades of experience with current gravitational-wave detectors to ensure project success.


Cosmic Explorer’s 40 km arms (20 km for the second site), 10 (5) times longer than Advanced LIGO’s, will increase the amplitude of the observed signals with effectively no increase in the noise. Although there are areas of detector technology where improvements would lead to incremental increases in the sensitivity and bandwidth of the instruments, the dominant improvement will come from significantly increasing the arm length.


Cosmic Explorer will be built with the technology developed for the A+ upgrade to Advanced LIGO, scaled up to a 40 km and 20km observatories with correspondingly better sensitivity. Planned upgrades to Cosmic Explorer will allow it to realize a full order of magnitude sensitivity improvement beyond Advanced LIGO.


Seeing Black Holes Merge throughout Cosmic Time

Advanced LIGO's observations of black holes merging in 2015, GW150914, gave humanity a glimpse of a previously unknown side of the Universe. Cosmic Explorer can detect merging stellar-mass black holes at redshifts of up to z ∼ 20. This immense reach will reveal for the first time the complete population of stellar-mass black holes, starting from an epoch when the universe was still assembling its first stars. Cosmic Explorer will detect hundreds of thousands of black-hole mergers each year, measuring their masses and spins. These observations will reveal the black-hole merger rate, the underlying star formation rate, how both have changed throughout cosmic time, and how both are correlated with galaxy evolution.

Investigating the Densest Matter in the Universe

Neutron stars are made of the densest stable matter in the universe. Six decades after their discovery, we still do not understand how matter behaves at the pressures and densities found in neutron-star interiors. The first neutron star merger, GW170817, was found in gravitational waves and observed across the electromagnetic spectrum. Observations of the mergers and remnants of neutron stars with gravitational waves and light illuminate unknown physics in the state of matter at ultra-high densities. Cosmic Explorer will capture these mergers with the precision needed to understand dense neutron-rich matter.

Exploring the Gravitational Wave Frontier

Cosmic Explorer might see other spectacular sources, the detection of any one of which would be revolutionary. Examples include the core collapse of a massive star in the Milky Way or Magellanic Clouds, emissions from mountains or quakes in pulsars, and glitches in magnetars in our galaxy. Cosmic Explorer might also see gravitational waves from forms of dark and exotic matter around black holes or in the cores of neutron stars, the mergers of primordial black holes formed in the early universe, or gravitational-wave emission from cosmic (super)strings.