ExoplanetVisualizer

Accesible at https://luisfe-suarez.github.io/ExoplanetVisualizer/

Exoplanet Transit Visualizer

Visualization tool of Transit Method, a common method for Exoplanet discovert. The simulation models the change in brigthness of a star over time, as an orbiting planet passes in front of it.

What is the Transit Method?

The transit method detects exoplanets by observing periodic dips in the brightness of a star. These dips occur when a planet passes (“transits”) in front of its host star, blocking a small fraction of the starlight. Similar to the decrease in brightness of a light bulb when an object covers it

For a transit to occur:

• The planet’s orbital plane must be nearly edge-on (inclination ~ 90°) from our perspective.
• The light curve of the star will show a small, temporary drop in brightness.

There are many factors that influence the dip in brightness and our ability to detect the exoplanet.

• Period: Planets with a smaller orbit (semi-major axis) have smaller periods, transiting in front of the star in less time, making it more likely for an observer to see the dip in brightness during limited observation time.

• Size: Planets which are bigger than its host star will cover more light from an observer perspective (like blocking the sunlight with our thumb versus using our whole hand). This makes the dip in brightness more evident and light curves with more prominent curves.

• Multiple objects in orbit: It could be the case that multiple objects are orbiting the same star, with overlapping transits in front of the star. When this is the case,

Physics & Math Behind the Simulation

This project simplifies the transit detection problem using basic orbital mechanics and geometry.

Orbital Position Calculation

I decided to assume a circular orbit (look at pylightcurve repo for more detailed orbits) and calculate the planet’s position using:

ω = 2π / P (angular velocity)

θ = ω × t (orbital angle)

x = a × cos(θ) (x-axis position)

y = a × sin(θ) (y-axis position)

Where:

• P: Orbital period (in days)
• a: Semi-major axis (in AU)
• t: Time (in days)
• θ: Orbital angle (in radians)

Transit Detection

A transit is assumed to occur when the planet is between 80° and 100° in orbital angle (i.e., near the line of sight). The decision to include a treshold is to simplify possible mathematical errors and to more easily update the curve in real time.

Transit occurs if |θ(deg) − 90°| < transit window

Flux Drop Calculation

When a transit occurs, I model the star’s brightness drop based on the relative sizes of the planet and star. Normal m:

Transit Depth = (Rp / Rs)^2

Where:

• Rp: Planet radius
• Rs: Star radius

I ran into some errors due to scaling of the planets and the actual dip in flux so I decided to use cosine interpolation to give more of a “u-shaped” curve instead of a sharp decrease that produced a “v-shaped” curve.

Flux = 1 − Transit Depth × (cos(π × n) + 1) / 2

Where n is the normalized distance from the transit center (n = 0 at center, n = 1 at edges).

Real-World Scaling

As I mentioned before, the light curves made no sense when I was using actual radii sizes from the planets, so I converted planet and star sizes into astronomical units (AU) using:

• 1 AU = 149,597,870.7 km
• Planet radius in Earth radii
• Star radius in Solar radii

Key Functions

calculateSimpleTransit() Determines position, orbital angle, and flux at a given time

generateLightCurve() Generates flux data over a range of times

getScaleInfo() Converts planet/star radii to AU and KM for display and understanding

Built With

• TypeScript
• React (frontend)
• Real exoplanet data from https://exoplanetarchive.ipac.caltech.edu/

📈 Future Enhancements

• Compare multiple planets side by side
• Simulate partial or grazing transits
• Add realistic star limb darkening
• Integrate real exoplanet/star data
• Animate planet orbits in 2D

Educational Purpose

This project is designed for educational use to help students:

• Understand orbital geometry
• Learn how light curves reveal exoplanets
• Explore simplified transit modeling and data visualization

AST010 Wanderers in Space - Prof. Jana Grcevich Tufts University