instrument

nanograv

The North American Nanohertz Observatory for Gravitational Waves, a collaboration using pulsar timing to detect gravitational waves.
74 related articles

Description

NANOGrav is a collaboration of astronomers and physicists that uses an array of precisely timed pulsars—rapidly spinning neutron stars—as cosmic clocks to detect gravitational waves. By measuring tiny variations in the arrival times of radio pulses from many pulsars, the collaboration can sense the stretching and squeezing of space-time caused by passing gravitational waves. In 2023, NANOGrav announced evidence for a gravitational wave background, likely originating from supermassive black hole mergers.

History

NANOGrav was founded in 2007 as a collaboration of US institutions, building on earlier pulsar timing efforts. It uses the Green Bank Telescope, Arecibo Observatory (until its collapse), and the Very Large Array.

How it works

Gravitational waves passing through Earth cause slight changes in the distance between Earth and each pulsar, altering the pulse arrival times. By monitoring dozens of pulsars over many years, NANOGrav looks for a correlated pattern of timing residuals across the sky—a signature of gravitational waves. The technique is analogous to using a galaxy-sized detector, with each pulsar acting as a 'tick' of a clock.

In practice

NANOGrav's primary application is detecting and studying gravitational waves at nanohertz frequencies, which are invisible to ground-based detectors like LIGO. This opens a new window into supermassive black hole mergers and the early universe.

Fun fact

The pulsars used by NANOGrav are so stable that they rival atomic clocks, with some showing timing precision better than a microsecond over decades.

Concept graph →

Related articles · 74

How to Hear a Day-Long Neutron Star Merger
Imagine an interpreter distracted by every rustle in the hall, turning a one-hour meeting into two. That's roughly how gravitational wave detectors behaved when analyzing long signals: each turn of the Earth added noise to the calculations, and processing a day-long neutron star merger threatened to stretch into weeks.
Mountains on Neutron Stars: How Magnetic Fields and Accretion Shape the Terrain
A sculptor shapes mountains from magnetic fields and heat, but the stone resists. A neutron star, the ultra-dense remnant of a supernova explosion, in a binary system pulls matter from its companion star. This infalling matter heats the star's crust unevenly, while the magnetic field tugs from within.
Instrumentation2026-08-122 minarXiv:2608.11673express
Gravitational Hearing: How to Catch the Whisper of Merging Black Holes
Gravitational-wave detectors are like extremely sensitive ears: they pick up the trembling of space when black holes or neutron stars collide somewhere in the universe. But even the most sophisticated "ears" cannot hear everything. The new LIGO A# project is like replacing the eardrum with a thinner, more sensitive membrane.
High Energy2026-08-121 minarXiv:2608.11968express
Radio Beacons from the Dark: 27 New Lighthouses in the Galaxy
A lighthouse flashes for a fraction of a second and goes dark again. The MeerKAT telescope in South Africa catches such flashes in the radio band. During its observations, it picked up 27 new sources that no one had seen before. Neutron stars are the remnants of exploded stars, compressed to the size of a city.
Cosmology2026-08-103 minarXiv:2608.09929
A Lottery with No Winners: Why the Gravitational-Wave Background Map Is Usually Blank
Imagine a lottery where instead of money, you win black holes. Each ticket is a random spot on the sky, and the prize is a gravitational wave from the merger of two giants. The chance of hitting the jackpot is minuscule, but if you do, the wave is heard across the entire universe.
High Energy2026-08-072 minarXiv:2608.06944express
Gravitational Hunt for Whirling Black Holes
Somewhere in the depths of space, two supermassive black holes are circling each other. Their dance is not smooth — the orbit is stretched, like a rubber band that alternately tightens and relaxes. Each revolution sends ripples through the fabric of spacetime — gravitational waves.
General Relativity2026-08-072 minarXiv:2608.07095express
Gravitational Ripples Reveal a Map
Dozens of radio dishes scattered across Earth have spent years listening to the ticking of distant pulsars — dead stars that spin and emit pulses more steadily than atomic clocks. When a gravitational wave passes between the star and us, the ticking is slightly disrupted.
High Energy2026-08-031 minarXiv:2608.02747express
Star Explosions Sing on Two Frequencies
When a star many times heavier than the Sun dies, it collapses and explodes as a supernova. This is not just a flash of light — the entire process, from core collapse to the ejection of the outer layers, makes space itself tremble. These ripples are called gravitational waves.
HEP Phenomenology2026-07-311 minarXiv:2607.29388express
Magnetic Hearing at Kilohertz Frequencies
A bell rings not from the strike but from a fleeting shudder of space. A gravitational wave, like ripples on a pond, passes through a massive magnet, and it deforms ever so slightly. That deformation can be turned into an electrical signal.
General Relativity2026-07-312 minarXiv:2608.00281express
Two Signals in the Universe's Noise
A noisy café. You're trying to make out two quiet conversations: one from the table by the window (black hole mergers), the other a barely audible whisper from the far corner (echoes of the universe's birth). But the hiss of the espresso machine and street noise (detector jitter) drown everything out. New work teaches a computer to separate these sounds.
General Relativity2026-07-272 minarXiv:2607.25073express
How to Smooth Out Gravitational Waves from the Early Universe
In the first moments of its life, the universe resembled a boiling cauldron. Matter wasn't spread evenly — clumps and voids were brewing within it, and their violent motion gave rise to a trembling of space itself: gravitational waves.
General Relativity2026-07-212 minarXiv:2607.19293express
Gravity Passes Another Test: 168 Mergers Confirm Einstein
A huge bowl of water. Drop a stone into it — ripples spread across the surface. The fabric of spacetime works much the same way: when two massive stars merge, they create ripples — gravitational waves. These waves travel to Earth and are picked up by giant detectors like LIGO and Virgo.
General Relativity2026-07-202 minarXiv:2607.18219express
The Cosmic Top That Brakes Too Fast
A spinning top that makes a hundred turns per second suddenly starts losing speed dramatically — much faster than any known top. That's exactly what pulsar J0435+3233 is doing. It's a dead star, crushed to the size of a city, but whirling at a furious rate.
Quantum Physics2026-07-201 minarXiv:2607.18351express
Gravity on the Edge of Quantum
Two tiny weights, each about the mass of a grain of sand, hang in the dark at a temperature colder than deep space. They don't touch, but an invisible thread connects them — gravity. The experiment physicists are now building aims to catch the moment when that thread tugs one weight due to the motion of the other.
Eccentricity: a magnifying glass for gravitational waves
In May 2020, the LIGO and Virgo detectors picked up a gravitational-wave burst known as GW200105. Among the many similar gravitational waves recorded, this one stood out for an oddity: the orbit of the colliding neutron star and black hole was not a perfect circle, but a stretched ellipse.
Cosmology2026-07-172 minarXiv:2607.16162
Waltz Without a Right Turn: Gravitational Waves and the Birth of the Universe
13.8 billion years ago, the universe swirled in a waltz. The right turn was forbidden. Today, the echoes of that cosmic ball reach us as a barely perceptible ripple in spacetime — gravitational waves. Their existence was predicted by Albert Einstein.
General Relativity2026-07-102 minarXiv:2607.09111express
A Noise Filter for Gravitational Waves
Gravitational-wave detectors are like sensitive microphones, listening for the whispers of distant cataclysms. But every now and then, a sharp crack bursts in — a brief noise spike known as a glitch.
High Energy2026-07-081 minarXiv:2607.07120express
A Lens for Ghosts: How Gravity Reveals the Universe's Secrets
Two neutron stars spiral closer and collide. The result: a gravitational wave, a ripple in spacetime, a short gamma-ray burst, and a faint glow astronomers call a kilonova. But sometimes the signal passes by a massive galaxy.
High Energy2026-07-082 minarXiv:2607.07477express
Cosmic Clocks and the Whisper of Gravity
A low rumble coming from underground could be the noise of a distant construction site, or it could be the echo of an ancient earthquake. Astronomers faced a similar puzzle in 2023 when they detected ultra-low-frequency gravitational waves — the trembling of spacetime itself, rippling across the universe.
Galaxies2026-07-063 minarXiv:2607.05208
The Ocean of Spacetime: The Hum of Black Holes and the Precision of Simulations
In the ocean of space, every storm of birth or merger of supermassive black holes generates ripples — gravitational waves traveling at the speed of light. Over billions of years, these waves superimpose, merging into a low-frequency hum, like a distant surf.
Gravitational Tango: How a Neural Network with Physical Intuition Heard the Rhythm of Black Holes
Isolating the signal from a single pair of supermassive black holes is like hearing a dancer's footsteps amid the roar of a hurricane. Somewhere in space, these monsters spin in a slow gravitational tango, distorting spacetime itself.
High Energy2026-06-281 minarXiv:2606.29146express
Neutron Star Tango: Mass and Spin
Think of a merry-go-round: it's easier to spin a light one, harder to spin a heavy one. Neutron stars, the ultra-dense remnants of exploded stars, behave in a similar way. Astronomers looked at fifty binary systems where one neutron star orbits another and noticed: the heavier the star, the longer its spin period. The link isn't strict, but it's statistically noticeable.
Gravitational Choreography: Pulsars vs. LISA
A pair of neutron stars, locked in a gravitational embrace, traces invisible circles in the void. A century ago, Albert Einstein described this dance as waves of curved geometry, but for a long time we could only catch glimpses — through the feverish flicker of radio pulses.
The Collapsar's Gravitational Boomerang: Cracking the GW190814 Anomaly
LIGO and Virgo detectors catch ripples in spacetime, but some signals force us to rewrite the scripts of stellar death. GW190814 — the merger of a black hole of 23 solar masses with a compact object of 2.6 solar masses — is a discordant chord in the symphony of standard models.
High Energy2026-06-162 minarXiv:2606.18241express
Gravitational Waves Reveal Black Hole Pairs
A hum resonates across the universe. It is not sound, but a trembling of space itself — the gravitational wave background. It is produced by pairs of supermassive black holes circling each other at the centers of distant galaxies. Each pair is like a bass instrument in a vast orchestra.
General Relativity2026-06-132 minarXiv:2606.15295express
Gravitational Waves to Put New Theory to the Test
In 2015, detectors caught a gravitational wave for the first time — a ripple in space that traveled from merging black holes. Since then, such signals have become a new window into the universe for astrophysics. But gravitational waves can do more: they carry the imprint of the very theory of gravity.
Echoes of Black Holes: How Gravitational Sirens Reveal the Curvature of the Universe
It was Edwin Hubble who discovered that galaxies are rushing apart, and Georges Lemaître linked this to the expansion of space. Today, the ΛCDM model, relying on dark energy and dark matter, asserts that the Universe is flat as a perfectly stretched canvas.
General Relativity2026-05-301 minarXiv:2606.00577express
Gravitational Waves: Listening to Space without Templates
Astronomers listen to the cosmos like an old radio: they twist the knob not to find a particular station, but to catch any unusual noise. This approach breaks the mold: instead of hunting for gravitational waves using memorized patterns, they catch everything — without bias.
HEP Phenomenology2026-05-262 minarXiv:2605.27519express
Gravitational Waves Hunt for Traces of Neutrino Birth
The universe sometimes resembles a pot of boiling water. With enough heat, liquid turns to vapor: that's a phase transition. Something similar could have happened in the early universe: a field filling space suddenly changed its state, like water becoming gas.
Cosmology2026-05-211 minarXiv:2605.22944express
Strings of the Cosmos: How to Catch the Universe's Tremors
A fundamental string plucked at the moment of the Big Bang doesn't just hum a single note — waves run along it, and occasionally tiny loops peel off. These loops, like tuning forks, begin to ring at their own frequency, producing a very high-pitched sound.
General Relativity2026-05-201 minarXiv:2605.21640express
When Black Holes Just Wave Hello
Usually, black holes inch closer gradually, circling in a tightening spiral. This dance births a long ripple of gravitational waves — a tremor in the very fabric of spacetime. Detectors LIGO and Virgo routinely catch such mergers. But GW190521 is the exception.
General Relativity2026-05-182 minarXiv:2605.19153express
Gravitational-Wave Monitoring: How GstLAL Catches Bursts in 16 Seconds
Spacetime is not a passive void but a dynamic membrane capable of elastic deformation. When neutron stars (ultra-dense objects the size of a city, where matter is compressed to nuclear density or black holes) regions with gravity so strong that even light cannot escape their bounds collide, the membrane shudders, generating…
General Relativity2026-05-142 minarXiv:2605.14728express
The Unheard Hum of Neutron Stars
A spinning top whirls at great speed and, instead of a steady hum, emits a quiet buzz — because it is slightly dented. Neutron stars work much the same way: city-sized spheres compressed to such density that a teaspoon of their material weighs as much as a mountain.
High Energy2026-05-121 minarXiv:2605.11947express
How the elongated merger orbit points to where the pair was born
When a neutron star and a black hole merge, they send out gravitational waves — ripples in spacetime that reach Earth. These ripples carry the imprint of their final dance: the orbit before the collision is often elongated, like an ellipse.
The Funeral March of Negative Mass: Why LIGO Doesn't Hear Anti-Chirps
Imagine an orchestra tuning up: the violins rise in pitch: that's the familiar 'chirp' of black hole mergers in LIGO detectors. Now picture a funeral march: a sound that descends, like a fading siren. That's exactly the gravitational-wave signature a system with one negative mass should leave.
General Relativity2026-05-052 minarXiv:2605.03305express
A Neutron Star as a Musical Instrument
Strike a bell, and it hums at a single pitch. But if you place a second clapper inside, and they ring without touching each other, the sound becomes more complex. That's roughly how the neutron star from the new study is built. It's not just a hot sphere: inside, two immiscible fluids can flow — for instance, superfluid neutrons and ordinary plasma.
General Relativity2026-05-042 minarXiv:2605.02453express
How to Hear a Crack in the Fabric of the Universe
The symphony plays, but a barely perceptible wrong note has crept into the score. This is roughly how physicists search for deviations from general relativity in the 'sounds' of the universe — gravitational waves from merging black holes.
Instrumentation2026-05-011 minarXiv:2605.00391express