Saturday Science Lecture with Tansu Daylan on Written in the alignment of planets and stars

Astronomical bodies typically have small sizes relative to the large distances between them, leading to their alignment along our line of sight, known as a syzygy, to become a rare phenomenon. Nevertheless, syzygies reveal crucial insights into the laws of physics as well as the characteristics of planets and stars in the Universe. The invention of the telescope and Johannes Kepler's remodeling of planetary motion in the 17th century paved the way for the prediction and first successful observation of transits of Mercury and Venus across the Solar disk in 1631 and 1639, respectively. While these observations led to significant advancements in physics and astronomy, similar attempts over the next few centuries have failed to detect planets beyond our solar system while transiting across the disk of their host star. Eventually, the development of Charged Coupled Devices (CCDs) in the latter half of the 20th century significantly improved the precision of stellar brightness measurements and led to the first discovery of a transiting exoplanet in 1999. Since then, comprehensive monitoring of exoplanetary transits and eclipses, enabled by missions such as the Kepler Space Telescope and Transiting Exoplanet Survey Satellite, has rapidly improved our understanding of exoplanet demographics. Complementary spectroscopic observations during transits and eclipses enabled by large-aperture, space-based observatories such as the Hubble Space Telescope and James Webb Space Telescope further allow us to probe their atmospheric compositions, presence of clouds, and habitability prospects, helping us address outstanding knowledge gaps in how planets form, evolve, migrate, and potentially support life.