WEEKLY SCIENCE MYSTERY / CASE 01
The star that kept dimming
A small dip returns on a clock. Follow the starlight before naming the object.
A telescope records a star getting briefly fainter, recovering, and doing it again. Choose a starting explanation, then let three clues test it. You do not need an astronomy background to open this case.
STARLIGHT · ABOUT 3–5 MINUTESRead the clue
Actual processed Kepler samples around one recurring dip. Relative brightness decreases then returns near its previous level. Hours are relative to a rough navigation center; the vertical axis is truncated.
BEFORE YOU OPEN THE CLUES
Start with an explanation.
Choose an initial explanation, then reconsider it as the clues open. Without JavaScript, you can read the three clues and open the discussion below.
Your choices stay in this browser when local saving is available. About saved progress.
CLUE 01The light comes back
The plotted points are actual processed Kepler observations from the site's teaching dataset. One short dip is followed by a return toward the previous brightness. The chart shows relative brightness, not a photograph of an object.
Consider: Does a steady drift explain a recovery?
CLUE 02It happens again
The supplied record contains 14 recurring dips over roughly a month. Their rough centers give an interval near 2.47 days. A repeating pattern is more informative than one unusual point, although those centers are navigation estimates rather than fitted transit times.
Consider: Which explanation naturally supplies a repeating clock?
CLUE 03A dip is not a brightening
During these events, the measured light decreases. An isolated bright flare has the opposite sign. A regularly crossing object can block some starlight and then uncover it. That explanation fits the direction and recurrence together.
Consider: Are you explaining all three clues with the same mechanism?
AFTER THE THREE CLUES
Keep your explanation, or change it.
Open the evidence discussion
THE BEST-SUPPORTED EXPLANATION AMONG THESE CHOICES
An orbiting object repeatedly crosses in front of the star.
A repeating crossing is the best fit among these choices. This record belongs to TrES-2, whose known planet TrES-2 b is studied in the Exoplanet Transit Lab. Repeating dimming supports a transit interpretation; it does not, on its own, prove that the crossing body is a planet.
What this does not establish
An eclipsing stellar companion or other contamination can imitate aspects of a transit. Planet confirmation requires additional evidence. This is a guided look at an already known system, not a discovery.
Take this with you: A good explanation must account for the direction, recovery and recurrence of the signal.
Return to your casebook →CHECK THE RECORD
Follow the sources.
These are source-based learning cases about established observations. The diagrams identify which information is measured and which is illustrative.
- NASA Exoplanet Archive: TrES-2 b ↗
Independent catalog and published orbital solutions.
- Dataset, processing and worked example ↗
The site's retained Kepler observations, quality selection and method limits.
- Download the plotted observation record ↗
CSV of processed observations; chart provenance is described below.
Source review: October 28, 2026 · Original learning activity by The Last Transmission.