Neutron Star Density Calculator
Explore the most extreme matter in the universe—where a teaspoon weighs billions of tons
Matter Crushed Beyond Imagination
When massive stars die in supernova explosions, their cores collapse to densities beyond anything else in the observable universe (except black holes). Neutron stars pack the mass of the Sun into a sphere just 20 kilometers across—about the size of a city. A teaspoon of neutron star material would weigh about 6 billion tons on Earth.
Our Neutron Star Density Calculator lets you explore these extreme objects. Calculate densities, compare to familiar materials, understand the exotic matter states within, and discover why neutron stars represent the ultimate laboratory for extreme physics.
Born from Stellar Death
Neutron stars form when stars between 8 and 25 solar masses exhaust their nuclear fuel and explode. The core collapses so violently that electrons are crushed into protons, forming neutrons. The Princeton astrophysics resources explain this process in detail. Our Star Life Expectancy Calculator shows which stars end this way.
Neutron Star Density Calculator
Explore the extreme densities of neutron stars:
⭐ Neutron Star Density Calculator
Compress anything to the density of a neutron star!
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Or enter custom mass (kg):
Calculate density comparisons, gravitational effects, and exotic matter states for different neutron star masses.
Understanding Neutron Star Numbers
Density Comparisons
- Air: 1.2 kg/m³
- Water: 1,000 kg/m³
- Iron: 7,900 kg/m³
- Gold: 19,300 kg/m³
- Earth’s core: ~13,000 kg/m³
- Sun’s core: ~160,000 kg/m³
- White dwarf: ~10⁹ kg/m³
- Neutron star: ~10¹⁷ kg/m³ (100 trillion times denser than lead!)
At neutron star density, all of humanity—every person who ever lived—would fit in a volume smaller than a sugar cube. Explore gravitational effects with our Gravity Simulator.
Surface Gravity
Neutron star surface gravity is about 2 × 10¹¹ times Earth’s gravity. If you could stand on one (you can’t—you’d be instantly vaporized), you’d be crushed thinner than a sheet of atoms. A marshmallow dropped from 1 meter would hit the surface with the energy of a small nuclear bomb.
The Internal Structure
Neutron stars have layered structures with exotic matter phases:
The Crust
The outer ~1 km consists of a crystalline lattice of neutron-rich atomic nuclei in a sea of electrons. This solid crust is incredibly strong—about 10 billion times stronger than steel. “Starquakes” in this crust can produce measurable gamma-ray bursts.
Nuclear Pasta
Below the crust, matter takes on bizarre configurations called “nuclear pasta” by physicists. As density increases, nuclei deform into sheets (lasagna), tubes (spaghetti), and interconnected networks. The Physical Review Letters has published research on this exotic matter state.
The Core
The inner core remains mysterious. At densities several times nuclear density, matter might include:
- Superfluid neutrons (flow without friction)
- Superconducting protons
- Strange quark matter (quarks deconfined from neutrons)
- Hypothetical particles like kaon or pion condensates
Explore quantum effects in matter with our Quantum Probability Visualizer.
Pulsars: Cosmic Lighthouses
Many neutron stars are observed as pulsars—rapidly spinning objects that emit beams of radiation from their magnetic poles. As they rotate, these beams sweep across Earth like lighthouse beams, creating regular pulses.
- Rotation rates: Some pulsars spin hundreds of times per second. The fastest known (PSR J1748-2446ad) rotates 716 times per second—its equator moves at nearly 25% light speed
- Magnetic fields: Up to 10¹⁵ Gauss—a trillion times stronger than Earth’s field. Magnetars have even stronger fields
- Precision timing: Pulsar timing is so precise it was used to first detect gravitational waves indirectly, earning the 1993 Nobel Prize
The ATNF Pulsar Catalogue lists over 3,000 known pulsars. Explore gravitational wave detection with our Gravitational Wave Detector.
Neutron Star Mergers
When two neutron stars spiral together and merge, they produce extraordinary events:
Gravitational waves: The 2017 detection GW170817 was humanity’s first observation of a neutron star merger in gravitational waves. The signal lasted about 100 seconds as the stars spiraled together.
Kilonova: The collision produces a brilliant explosion visible across the electromagnetic spectrum. The NASA announcement described the historic multi-messenger observation.
Heavy element factory: Neutron star mergers create most of the universe’s heavy elements—gold, platinum, uranium. The gold in your jewelry was likely forged in a neutron star collision billions of years ago. Calculate stellar element production with our Fusion Energy Calculator.
Frequently Asked Questions
What happens if you add mass to a neutron star?
If a neutron star exceeds the Tolman-Oppenheimer-Volkoff limit (about 2-3 solar masses), neutron degeneracy pressure can no longer support it against gravity. It collapses into a black hole. Our Black Hole Survival Timer explores what happens next.
Could we extract material from a neutron star?
No practical way exists. The gravitational binding energy is enormous—removing material requires more energy than nuclear weapons could provide. Also, neutron star matter is unstable at normal densities; removed material would explosively decompress into normal matter (mostly neutrons decaying into protons, electrons, and neutrinos).
How close is the nearest neutron star?
The nearest known neutron star is about 400 light-years away (RX J1856.5-3754). Many unknown neutron stars likely exist closer since they’re small and often dim. The Milky Way probably contains about a billion neutron stars. Explore cosmic distances with our Cosmic Distance Ladder.
Do neutron stars cool down?
Yes, but slowly. Newly formed neutron stars have surface temperatures around 1 million Kelvin. They cool primarily through neutrino emission initially, then photon emission. After millions of years, they become too cool to detect in visible or X-ray light, but they persist indefinitely as cold, dark remnants.
Explore More Extreme Physics
Neutron stars are laboratories for physics at its most extreme. Continue exploring:
- Hawking Radiation Timer – Black hole physics and evaporation
- Time Dilation Calculator – Relativistic effects near extreme masses
- Dark Matter Calculator – The invisible mass of the universe
- Antimatter Calculator – Matter-antimatter annihilation energy
- Heat Death Countdown – The ultimate fate of the universe
Neutron stars represent matter pushed to its absolute limits—dense enough to warp spacetime, strong enough to crush atomic nuclei, and magnetic enough to manipulate matter across light-years. These cosmic extremes reveal the universe’s most exotic physics.