Exoplanet Detection Lab: Transit & Radial Velocity Community
Questions, answers and tips from people who use the Exoplanet Detection Lab: Transit & Radial Velocity. Tune a planet's size, mass and orbit and see whether the transit dip or the radial-velocity wobble is strong enough to detect above real instrument noise..
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This page shows only real posts from real people, so it starts empty. The guide below has the questions people most often have about the Exoplanet Detection Lab: Transit & Radial Velocity. Pick one to start a thread, or write your own.
From the tool guide: common questions about Exoplanet Detection Lab: Transit & Radial Velocity
The items below are not posts by community members. They come from the written guide for this tool and are here to get a conversation started. Use “Ask a follow-up” to open a thread about any of them.
Why is Earth-sized planet harder to detect than a Jupiter-sized one by transit?
Transit depth scales with the square of the radius ratio, so a Jupiter-sized planet (about 11 Earth radii) produces a dip over 100 times deeper than an Earth-sized planet around the same star, far easier to spot above instrument noise.
From the tool guide Ask a follow-upWhy do 'hot Jupiters' dominate early radial-velocity discoveries?
RV semi-amplitude grows with planet mass and shrinks with orbital period, so a massive planet in a very short, close orbit around its star produces the largest, easiest-to-detect stellar wobble.
From the tool guide Ask a follow-upKey ideas
- The transit method measures a dip in starlight: depth = (R_planet / R_star)², so a Jupiter-sized planet blocks far more light than an Earth-sized one around the same star.
- The radial-velocity method measures the star's own tiny wobble caused by the planet's gravity, with amplitude K depending on planet mass, orbital period and star mass.
- A signal only counts as a real detection when it clears the noise by enough - astronomers typically require a signal-to-noise ratio (SNR) of at least 3.
- The two methods are complementary: transit gives a planet's radius, radial velocity gives its mass, and together they reveal its density and likely composition.
Things to try
- In Transit mode, shrink the planet to Earth-size and watch the SNR readout fall.
- In Radial Velocity mode, shorten the orbital period and see the RV signal grow.
- Raise the noise slider until an easily-detectable planet becomes undetectable.
- Compare the same planet's detectability by both methods.
Where this is used
Missions like Kepler and TESS use the transit method to find thousands of candidate planets, while ground-based spectrographs use the radial-velocity method to confirm planet masses - exactly the two techniques modeled here.
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