PSR B0531+21 — Crab Pulsar · Neutron Star

When a massive star (8–20× the Sun) runs out of fuel, it collapses in a Supernova explosion. The leftover core becomes a Neutron Star: 1.4 solar masses packed into ~11 km radius. Its rapid spin + extreme magnetic field launches twin jets, making it a Pulsar. Tap ● dots for details.

1.4 M☉

MASS

1.4× the Sun's mass packed into a city-sized ball. One teaspoon = ~100 million metric tons.

~11 km

RADIUS

Smaller than most cities! Earth's radius is 6,371 km — 580× larger — yet this object outmasses the Sun.

30 Hz

SPIN RATE

30 full rotations every second. Earth takes 24 hours for just one. Any ordinary object would fly apart instantly.

10¹² G

MAG. FIELD

2 trillion times stronger than Earth's magnetic field. Strong enough to strip electrons from atoms thousands of km away.

~10⁶ K

SURFACE TEMP

About 173× hotter than the Sun's surface. Glows in X-ray light, invisible to the naked eye.

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PULSAR JET

Charged particles race along magnetic poles at near light speed.

Beam sweeps space like a lighthouse — emits 100,000× Sun's energy.

ACCRETION DISK

Surrounding gas spirals inward, forming a glowing disk.

Friction heats the inner edge to ~10⁷ K — blazing in X-ray light.

MAGNETIC FIELD LINES

A dipole field at 10¹² Gauss — one trillion times Earth's field.

Tilted axis causes the pulsed beam and powers the Crab Nebula.

NEUTRON STAR SURFACE

Outer crust: crystalline iron lattice, 10 billion times stronger than steel.

Interior: pure neutron fluid at nuclear density.

Scale Comparison

Sun vs Neutron Star — to scale

● NEUTRON STAR
r = 11 km (dot) SUN ●
r = 696,000 km

Radius

● Neutron Star11 km

● Sun696,000 km

63,000× smaller than the Sun. If the Sun were a basketball, the neutron star would be a grain of sand.

Mass

● Neutron Star1.4 M☉

● Sun1.0 M☉

Despite being 63,000× smaller, the neutron star is actually heavier. Density equals that of an atomic nucleus.

Surface Gravity

● Neutron Star2×10¹¹ g

● Sun28 g

7 billion times stronger than the Sun's surface gravity.

Density

● Neutron Star~10¹⁷ kg/m³

● Sun1,410 kg/m³

100 trillion times denser than the Sun — same density as an atomic nucleus.