Estimate the depth of a dip

Estimate the depth of a dip — guided practice

Calculate fractional dimming and a simplified size ratio.

Continue the workbook. The first three measurements at days 0, 0.25, 0.5 are designated out-of-event baseline samples for this fixture. Baseline=1.000; minimum=0.990. The approximation ignores limb darkening, grazing geometry and blended light.

1. 1. Estimate the baseline

   Enter label Baseline in C2 and =AVERAGE(B2:B4) in D2. Enter Minimum in C3 and =MIN(B2:B21) in D3. Use number formatting with at least three decimals.

   You should see: D2 is 1.000 and D3 is 0.990.

   A stated baseline selection is more reproducible than choosing it by eye.

2. 2. Compute fractional depth

   Enter Fractional depth in C4 and =(D2-D3)/D2 in D4. Enter Depth percent in C5 and =D4*100 in D5; keep D5 as a regular number, not percent format.

   You should see: Fractional depth is 0.010 and depth percent is 1.

   Normalizing by the baseline also works when the baseline is not exactly 1.

3. 3. Use the simple area model

   Write depth≈(planet radius/star radius)^2 in your note. Enter Radius ratio in C6 and =SQRT(D4) in D6. Explain that 0.1 means about one-tenth of the star’s radius under the assumptions.

   You should see: D6 is 0.1; the size ratio is 10%, not 1%.

   The blocked area changes with radius squared, so depth and radius ratio differ.

4. 4. State what is missing

   Write that no absolute radius can be calculated without a stellar radius estimate, and this minimum-based classroom estimate is not a fitted transit model. Save the workbook.

   You should see: The result includes its assumptions and does not claim a planet size in kilometers.

   A numerical answer is only as specific as the input information permits.