Exoplanet discovery
Exoplanet Hunter
Most known exoplanets were found by the tiny dip in starlight as they pass in front of their star. Recreate the method, judge habitability, and explore the real catalogue.
Transit photometry
Transit simulator
Watch a planet cross its star and build the light curve a telescope like Kepler or TESS would record. Add noise and see whether the signal survives.
Transit depth (model)
10,520 ppm
Rₚ/R★
0.1026
Impact parameter b
0.169
a / R★
9.701
Measured depth
12,560 ppm
Recovered Rₚ/R★
0.1121
Signal-to-noise
117
Period estimate
3.50 d (time between transits)
Model: circular orbit, linear limb darkening (u = 0.6) in the small-planet approximation of Mandel & Agol (2002), Gaussian noise. Measured values come from averaging the noisy in-transit and out-of-transit points.
Habitability
Habitable-zone explorer
Find where liquid water could exist on a rocky planet's surface around different kinds of stars.
Dark band: conservative habitable zone (runaway → maximum greenhouse). Light band: optimistic zone (recent Venus → early Mars). Kopparapu et al. 2014, 1 Earth mass.
Conservative zone
0.951–1.68 AU
Optimistic zone
0.751–1.77 AU
Equilibrium temperature
254.6 K (-18.6 °C)
Location
Conservative HZ
Lying inside a habitable zone does not make a planet habitable. Its atmosphere, mass, water inventory, magnetic field, tidal locking and the star's flare activity all matter — and none of these can be inferred from distance alone. Equilibrium temperature ignores any greenhouse effect (Earth's is 255 K; its real average is about 288 K).
Real data
Exoplanet database
Search confirmed exoplanets live from the NASA Exoplanet Archive and load any transiting planet into the simulator.
Data: NASA Exoplanet Archive, Planetary Systems Composite Parameters (pscomppars), operated by Caltech/IPAC under contract with NASA. This research tool uses the archive's public TAP service; values combine multiple published solutions and may differ from individual papers.
The physics of a transit
When a planet crosses its star, it blocks a fraction of the light equal to the ratio of the two disks' areas: depth ≈ (Rₚ/R★)². A Jupiter-size planet dims a Sun-like star by about 1%; an Earth-size planet by only 84 parts per million. The duration depends on how fast the planet moves and how much of the stellar disk it crosses, which ties it to the star's mass and radius through Kepler's third law.
Stars are darker towards their edges (limb darkening), which rounds the bottom of the transit. Repeated transits give the orbital period, and with the period and the star's mass the orbit's size follows. Try the transit depth calculator and the habitable zone estimator for the underlying equations.