Field Guide: reading a light curve

A light curve is just a star's brightness plotted over time. A planet crossing in front of its star makes a tiny, repeating dip. Your whole job in the Data Lab Signal Lab AI Lab is telling real planets from the things that fake them. Here's the cheat sheet.

Real planet transit

Planet ✓

Shallow dips that are evenly spaced and flat-bottomed — the planet blocks the same sliver of starlight every orbit.

Look for: a steady rhythm · same depth each time · a flat or U-shaped bottom.

Eclipsing binary

Not a planet

Two stars orbiting each other, taking turns blocking. The #1 impostor. Dips are deep and often V-shaped, with a shallower second dip halfway between.

Tell: a secondary dip · alternating deep/shallow · V-shape · way too deep for a planet.

Glitch / systematic

Not a planet

A single sharp spike or step that doesn't repeat — a cosmic ray, a thruster fire, or an instrument hiccup.

Tell: one-off · sharp · never comes back on the same beat.

Just noise

Not a planet

The star's natural flicker and measurement scatter, with no repeating dip at all. Saying "no planet" here is a real, valuable answer.

Tell: fuzzy but flat · no pattern · nothing that repeats.

Single transit (the prize)

Planet ✓

Just one clean dip in the whole record — a planet on a long orbit that only crossed once while TESS watched. Automated software often throws these away.

Why it matters: humans catch these; computers miss them. Most citizen-science planet finds are single-transits like this.

Star spots / variability

Usually not

Smooth, rolling ups and downs as a spotty star rotates. It's wavy, not a sharp dip, and it doesn't have a flat transit floor.

Tell: gentle waves · no crisp dip · the curve drifts rather than drops.

30-second cheat sheet
Real planetSmall, repeating, evenly-spaced, flat-bottomed dips. Same depth every time.
Eclipsing binaryDeep + V-shaped + a secondary dip halfway between. Too deep to be a planet.
GlitchOne sharp spike that never repeats.
NoiseFuzzy and flat — no pattern.
Single transitOne lone clean dip — could be a real long-period planet. Flag it!
Try it in the Data Lab →