☄️ Meteor Entry & Ablation

A meteoroid enters the atmosphere: drag, ablation, and luminous efficiency govern the light curve. The ablation equation dm/dt = −(σ/2)·ρ_atm·v³·m determines mass loss.

SpaceInteractive
Left: atmospheric entry visualization · Right: luminosity light curve vs altitude · R = reset

How it Works

The simulation integrates three coupled ODEs: (1) altitude z decreasing at rate v·sin(θ); (2) velocity decreasing due to aerodynamic drag; (3) mass decreasing due to ablation heating. The atmospheric density follows an exponential profile ρ_atm = ρ₀·exp(-z/H) with scale height H ≈ 8 km.

The luminosity L = -(τ/2)·v²·(dm/dt) where τ is the luminous efficiency. Larger, faster, and more ablation-prone (cometary) bodies produce brighter meteors. The simulation stops when the meteoroid either disintegrates (m → 0) or reaches the ground.

Ablation: dm/dt = -(σ/2)·ρ_atm·v³·m Drag: dv/dt = -(C_D·A·ρ_atm·v²)/(2m) Altitude: dz/dt = -v·sin(θ) Luminosity: L = -(τ/2)·v²·dm/dt Atmosphere: ρ_atm = 1.225·exp(-z/8500) kg/m³

Frequently Asked Questions

What is meteor ablation?

Ablation is the process by which a meteoroid loses mass as it enters the atmosphere. The intense frictional heating vaporizes the surface material, creating a glowing plasma trail. The ablation coefficient σ measures how efficiently kinetic energy converts to mass loss.

What is the ablation equation?

The ablation equation dm/dt = -(σ/2)·ρ_atm·v³·m describes the rate of mass loss, where σ is the ablation coefficient (~0.005-0.05 s²/km²), ρ_atm is atmospheric density, v is velocity, and m is the current mass.

What causes a meteor to glow?

A meteor glows because the meteoroid ablates at high speed, heating the surrounding air to incandescence. The luminosity L = -(τ/2)·v²·dm/dt where τ is the luminous efficiency (typically 0.1-10% depending on velocity and composition).

What is the difference between a meteor and a meteoroid?

A meteoroid is the solid object in space. A meteor is the visible streak of light produced when the meteoroid enters the atmosphere. If part of it survives to reach the ground, it becomes a meteorite.

What is the drag equation for atmospheric entry?

The drag deceleration is dv/dt = -(C_D·A·ρ_atm·v²)/(2m) where C_D is the drag coefficient (~0.5-1.0), A is the cross-sectional area, and m is the instantaneous mass of the meteoroid.

What is the meteor light curve?

The meteor light curve plots luminosity versus time or altitude. It typically shows rapid brightening as the meteoroid enters denser atmosphere, a peak, then fading as it decelerates and disintegrates. Complex shapes indicate fragmentation.

At what altitudes do meteors ablate?

Most visible meteors ablate between 80–120 km altitude. Small dust particles burn up at higher altitudes (~120 km) while larger bodies can penetrate deeper. The altitude depends on entry angle, velocity, composition, and size.

What is a fireball and a bolide?

A fireball is a meteor brighter than magnitude -4 (brighter than Venus). A bolide is an exceptionally bright fireball that typically explodes in the atmosphere. The 2013 Chelyabinsk event was a famous superbolide releasing 30× more energy than the Hiroshima bomb.

How does entry angle affect ablation?

Shallow entry angles spread ablation over a longer path through the upper atmosphere, producing long-duration events. Steep angles concentrate heating, causing more rapid ablation. The optimal survival angle for large objects is approximately 15–30°.

What is the Poynting-Robertson effect?

The Poynting-Robertson effect causes small meteoroid particles to spiral inward toward the Sun due to radiation pressure asymmetry. This is why meteor streams gradually disperse over thousands of years unless replenished by cometary activity.

About this simulation

This simulator integrates three coupled equations for an incoming meteoroid: drag deceleration, ablative mass loss, and altitude. As the body falls into exponentially denser air (ρ_atm = ρ₀·exp(-z/H)), friction heats its surface, and the ablation term dm/dt = -(σ/2)·ρ_atm·v³·m starts stripping away mass. The freed kinetic energy converts into light through the luminous efficiency τ, producing the light curve you see traced on the right-hand panel as altitude drops.

🔬 What it shows

A side-by-side view: on the left, the meteoroid's descent through labelled altitude bands (0-120 km) with a glowing trail whose brightness tracks instantaneous luminosity; on the right, the full light curve (luminosity vs. altitude) with the traversed portion highlighted in real time.

🎮 How to use

Adjust the sliders for initial mass, entry velocity, entry angle, and ablation coefficient σ, or switch composition between stony, iron, and cometary bodies (each with a different density used to compute cross-sectional area). Press "Reset" or the R key to re-run the integration with new parameters.

💡 Did you know?

Because ablation scales with v³ while drag only scales with v², faster meteoroids lose mass far more aggressively — this is why very fast meteor showers like the Leonids often burn up completely, leaving no meteorites.

Frequently asked questions

Why does the simulation use exponential atmospheric density?

Earth's atmosphere isn't uniform — its density falls off roughly exponentially with height, ρ_atm = 1.225·exp(-z/8500) kg/m³ in this model, with a scale height of about 8.5 km. This is why meteors are invisible above ~120 km (too little air to cause drag or ablation) and why the light curve rises so sharply once the body drops below about 100 km.

What does the ablation coefficient σ actually control?

σ (set here between 0.001 and 0.1 s²/km²) scales how efficiently kinetic energy converts into mass loss, dm/dt = -(σ/2)·ρ_atm·v³·m. A higher σ means the meteoroid ablates faster for the same speed and density — typical stony bodies sit in the middle of this range, while more fragile cometary material ablates faster.

Why does composition change the result if mass stays the same?

The three preset densities (stone 3000, iron 7900, cometary 400 kg/m³) feed into the radius formula r = (3m/4πρ)^(1/3), which sets the cross-sectional area A used in the drag term. A denser iron body of the same mass is smaller and more compact, so it experiences less drag and can punch deeper into the atmosphere before disintegrating.

What determines when the simulation stops?

The integration loop halts when altitude reaches the ground (z ≤ 0), the remaining mass drops below 0.01% of the starting mass (full disintegration), 200 seconds of simulated time elapse, or velocity falls under 100 m/s — whichever comes first, matching what real observational light curves capture.

How does entry angle affect the outcome?

The angle slider (10-90°) sets sin(θ) in both the altitude-loss rate dz/dt = -v·sin(θ) and the gravity term in the drag equation. Shallow angles stretch the descent over a longer atmospheric path (longer, dimmer light curves), while steep angles concentrate heating over a short path — the reason the optimal survival angle for large meteoroids is often cited as roughly 15-30°.