Week 3: Standing on Rayleigh Scattering

Hey guys, welcome back to my blog! Last week, I showed you guys what the exoplanet Trappist-1e looks like without an atmosphere. For a visible image, there must be a simulated light source (the star Trappist-1). Now, let’s snap our fingers and add the atmosphere back.

But first, what is an atmosphere anyway? It’s an envelope of gases that surrounds a celestial body. Most celestial bodies—planets, moons, stars, even comets—have atmospheres. In the case of most planetary/exoplanetary atmospheres, the gravity, molar mass, pressures, and temperatures define the vertical structure. When said structure is predominantly gravity-dependent, the atmosphere is considered to be in hydrostatic equilibrium—hence the term ‘hydrostatic equilibrated atmosphere.’ This is the kind of atmosphere Trappist-1e has.

So, what happens when photons strike atmospheric particulate matter? Let’s visualize the scenario: a ray of light (from a star, say Trappist-1) travels through empty space and suddenly collides with a particle (which is, say, in the atmosphere of Trappist-1e). The outcome of this collision varies depending on the size of the particle and the wavelength of the light. If we consider small particles like atoms and molecules, the Rayleigh Scattering model best predicts the light’s subsequent behavior.

As of right now, I’m struggling with some errors in the simulation that includes the atmosphere, as you can see here:

This indicates that the software is not corresponding the correct information with each pixel. Keep your fingers crossed that next week I’ll be able to show you the Rayleigh scattering in more detail for this exoplanet.

Lastly, for a more structured progression, I’d like to generate graphs of spectral radiance versus wavelength for the cases of Trappist-1e with and without an atmosphere. After that, I’ll attempt to add clouds to the fray.

I wonder if aliens would enjoy eating pie as much as I do. Happy Pi Day, and see you next week!

Tanvi Deshmukh