Week 1: The Transit Method

Mar 31, 2023

Welcome back to my Senior Project blog! At the beginning of this week, I planned the independent research portion of my project. This will take the form of an in-depth research paper on the history of exoplanet discovery and my predictions of where it will go in the future as well as a comprehensive research journal recording my studies and observations. In order to completely understand the topic of exoplanets, I will take an online Yale course on the Frontiers and Controversies in Astrophysics, which covers the rapidly advancing field of extra-solar planets or exoplanets. You can find more information or even follow along with the course here. I plan to supplement this course with readings from the Astrophysics of Exoplanets course from U Chicago’s astronomy department. You can find the course syllabus and links to the readings here.

For the rest of the week, I began taking notes on the basics of astrophysics needed for these courses. I used the Openstax Astronomy textbook to study prominent astrophysicists in history such as Tycho Brahe, Johannes Kepler, and Isaac Newton. I reviewed Kepler’s laws of planetary motion and general vocabulary for orbits. I also went over equations for the mass and luminosity of stars, and the basics of the transit method of exoplanet detection. Essentially, both ground and space telescopes can detect an exoplanet by measuring a change in brightness or luminosity of a star if the planet star system’s orbital plane is viewed edge-on. The amount of light blocked (i.e. the change in brightness) is known as the transit depth. The transit depths can tell us the size of the planet if we know the size of the star. The interval between successive transits tells us the period of the orbit. Astrophysicists use that information to apply Kepler’s laws and find the distance between the planet and the star. That distance is crucial to discovering the conditions on the planet. If it’s very close to its star, we can expect an extremely hot and uninhabitable planet. If it’s very far from its star, we can expect an extremely cold and equally uninhabitable planet. Exoplanets found to be the “perfect” distance from their star have the potential to carry life since the conditions are not as extreme.

In the coming weeks, I will be working more with my on-site advisor to begin practicing the transit method and hopefully finding my own exoplanets. I will leave you with an astrophysics fact of the week: Moons orbit exoplanets are known as exomoons, but they are so difficult to detect there have never been any confirmed to exist. Thank you for reading my blog, and stay tuned for on-site updates coming next week!


  • Maren Willard

2 Replies to “Week 1: The Transit Method”

  1. Katey B. says:

    Wow, your fact about moons was so fun! Do you know what the most common type of exoplanet is?

    1. Maren W. says:

      It’s a type of planet called a super earth, which just means that it’s about 1.5 to 4 times the radius of our Earth. Even though this is the most common type, we actually don’t have any super earths in our own solar system so scientist don’t quite know their composition or really any details about their atmosphere.

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