Science · answer • reason • check

Exoplanet Transit

Given a star and a transit signal, estimate the planet's size, orbit, and temperature, then verify the result by regenerating the observables in the browser.

Key ideas:
transit depth ≈ (planet radius / star radius)²
orbital size from period via Kepler's third law
equilibrium temperature from stellar heating and inverse-square dilution

Answer

The inferred planet for the current transit setup

Preset scenario

Synthetic data

Star radius (R☉)

1.00

Star mass (M☉)

1.00

Star temperature (K)

5772

Transit depth (ppm)

Orbital period (days)

365.25

Bond albedo

0.30

Planet radius

—

Orbit size

—

Transit duration

—

central-transit approximation

Equilibrium temperature

—

planet class —orbit class —heating level —

The numbers above come directly from the slider inputs using the formulas in the Reason section.

Reason

How the page turns a transit signal into physical estimates

Depth → radius

If the planet blocks a fraction of the star's light, the simplest estimate treats the transit depth as the ratio of the blocked disk area to the stellar disk area.

δ ≈ (R_p / R_*)² → R_p ≈ R_* √δ

—

Period → orbit

For a planet whose mass is tiny compared with the star's, Kepler's third law links orbital period to semi-major axis.

a³ ≈ M_* P² (a in AU, P in years, M_* in solar masses)

—

Stellar heating → equilibrium temperature

A simple radiative-balance estimate combines the inverse-square falloff of stellar energy with blackbody re-radiation.

T_eq ≈ T_* (1−A)^1/4 √(R_* / 2a)

—

Synthetic light curve

The page generates a stylized transit using the inferred depth and central-transit duration, then optionally adds mild noise.

synthetic observationsmodel transit

Orbit sketch

The orbit panel is not to scale between different presets, but it uses the inferred star and orbit sizes consistently within the current scenario.

planet position and orbit

Check

Independent consistency tests designed to fail loudly when assumptions break

Depth identity

—

Kepler identity

—

Transit geometry

—

Recovered from synthetic data

—

Audit table

Quantity	Input / estimate	Independent recomputation

The check layer is intentionally independent in style: it recomputes identities, tests geometric sanity, and re-measures the synthetic light curve rather than simply trusting the display values.

NASA Exoplanet Watch glossary NASA/JPL Kepler lesson NASA habitable-zone tutorial