A light curve is a record of measured brightness as a function of time. For a transit, the key pattern is a small decrease relative to the star’s usual brightness, followed by a return toward that baseline.
Flux is the observable¶
In this course, flux means the light power received per unit collecting area. A detector estimates that received light at a sequence of times. The value can depend on the instrument, observing conditions, and chosen units, so we often compare each measurement with an out-of-transit baseline .
Normalized flux is dimensionless. A value near 1 represents the chosen baseline; a value below 1 represents a dimmer measurement. It does not mean the star has stopped emitting light.
Transit depth¶
The transit depth is the fractional decrease from the baseline:
For example, normalized flux 0.990 has depth 0.010, meaning a one-percent decrease relative to the defined baseline.
Reading a light curve responsibly¶
A dip alone is not a finished conclusion. Before calling it evidence for a planet, ask:
Is the baseline defined and visible?
Does the dip recur at a consistent time interval?
How large is the measurement uncertainty and instrumental variation?
Could stellar activity or another source produce a similar pattern?
Project 1 begins before those observational complications. It uses a known geometric model to practice how computational assumptions become visible, testable output.