Transit depth and planet-radius inference
A dark opaque planet crossing a uniformly bright stellar disk removes light in proportion to its projected area while fully superimposed on the disk.
Key knowledge
A dark opaque planet crossing a uniformly bright stellar disk removes light in proportion to its projected area while fully superimposed on the disk. The ideal fractional depth is δ=(Fout−Fin)/Fout=(Rp/Rstar)². This measures a radius ratio; an absolute planet radius requires an independently constrained stellar radius. Repeated dimming needs validation against alternative causes.
Values and equations
δ=(Fout−Fin)/Fout=(Rp/Rstar)²
- δ
- ideal fractional flux loss during full overlap 1
- Fout,Fin
- out-of-transit and in-transit flux in the same band W m⁻²
- Rp,Rstar
- planet and stellar radii m
Conditions and scope
- Use a spherical opaque planet smaller than the star, a full non-grazing overlap, stable uniformly bright stellar surface, negligible planet light and no contaminating flux. Limb darkening, spots, grazing geometry, exposure averaging and dilution require an adapted light-curve model.
- Detection favours suitable orbital alignment and sufficiently strong signals. The radius relation alone establishes neither planet mass nor atmospheric composition; repeated periodic dips alone do not exclude all false positives.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Read the Archive's projected-area definition and OpenStax's actual transit/area-ratio and false-transit paragraphs. Derived the dimensionless disk-area ratio under explicit geometrical assumptions. Excluded dated discovery counts, a universal three-transit confirmation rule and unique composition inference from bulk density; did not claim a complete limb-darkened model.
2026-10-10 · Independent AI editorial review: All44 exact root-authored compact records, equations/variable units/conditions and140 origin edges accepted after independently reading final6/18 with bounded primary bodies and matching prior38/122 scientific fingerprints unchanged. Exact claim/edge review is distinct from combined inventory scope and separate CLE26 approval; no entire cited books or old-corpus experimental revalidation is asserted. Receipt: cosmos-completion-independent-content-and-inventory-review.1.
Entry details
Permanent link to this entry ↗- Record identity
- uni-cosmos-transit-radius-inference
- Revision
- core.1
- Structured reference record
- University core expansion