Join us this week for Cosmolunch! We will have Tansu Daylan (MIT) presenting his work on detecting exoplanets.
Speaker: Tansu Daylan (MIT)
Title: Discovery of the HD 108236 multiplanetary system with a bright Sun-like star
Abstract: Our species has long been contemplating planets beyond our solar system. In recent years, an extensive research program has produced a catalog of more than four thousand exoplanets and contextualized the planet Earth and the solar system, while giving us observables to test models of planet formation and evolution. Among known exoplanets, multiplanetary systems with bright host stars are especially interesting, as they allow us to study exoplanet atmospheres. The Transiting Exoplanet Survey Satellite (TESS) is a space-based, red-optical survey of the sky to search for exoplanets by leveraging its wide field-of-view and high photometric precision. A highlight from the TESS mission is the discovery of four exoplanets hosted by the nearby, bright, and Sun-like star HD 108236, also known as the TESS Object of Interest (TOI) 1233. The discovery was enabled by an extensive ground-based follow-up program including transit photometry, high-resolution imaging, reconnaissance, and precise Doppler spectroscopy. The innermost planet in the system is a rocky super-Earth with a period of 3.8 days and has a radius of 1.6 times the radius of the Earth. The outer three planets are sub-Neptunes, with potential gaseous envelopes, having radii of 2.1, 2.7, and 3.1 times that of the Earth and periods of 6.2, 14.2, and 19.6 days. With a visual magnitude of 9.2, the bright host star makes the planets favorable targets for mass measurements and atmospheric characterization via transmission spectroscopy. In particular, HD 108236 is the brightest Sun-like star in the visual band known to host four or more transiting exoplanets. The coplanar nature of the system suggests potential existence of outer transiting planets, as evidenced by the recent discovery of another transiting planet in the system by the CHEOPS telescope. Its planets span a broad range of radii and equilibrium temperatures, originate from the same protoplanetary disk, and share a common history of stellar insolation. Thus, the HD 108236 system stands as an exciting, opportune cosmic laboratory for controlled and comparative atmospheric characterization by JWST.