Dynamical Signatures of Planet Formation in Wide-Separation Exoplanets and Brown Dwarfs

Project: Research project

Project Details


Planet formation is a complex process spanning many orders of magnitude in size scales and time scales. Furthermore, the whole process typically occurs while completely shrouded in dust and gas, making it extremely difficult to observe directly. One thing we can observe are the adolescent directly imaged planets (ages of 5-100 Myr) that are the products of the planet formation process. In this proposal, we aim to study the orbits of these young exoplanets to learn about how planets formed. We propose to leverage the orders of magnitude improvement in astrometric precision enabled by long-baseline optical interferometry to constrain their orbits in unprecedented detail (50 microarcsecond astrometry, a 10-100x improvement on previous constraints). We will look at a large sample of wide-separation (> 3 au) exoplanet and brown dwarf companions (1-80 Jupiter masses) to look at population-level trends and identify the dominant dynamical mechanisms that shape these systems. This dynamical study is highly complementary to the planned array of programs to characterize the atmospheres of giant planets with JWST to study formation through their compositions. Planet-planet scattering and resonant migration in a gas disk can create a population of eccentric planets. For closer in (< 1 au) giant planets, radial velocity and transit surveys have found many quiescent systems, unlike the stellar binary population that has undergone much dynamical upheaval. The wide-separation giant planets and brown dwarfs should bridge these two populations. Previous work using imaging alone has identified that brown dwarf and exoplanet companions have different distributions, but the eccentricity distributions are poorly constrained. We propose to use the drastic improvement in the knowledge of these orbits enabled through interferometry to confirm they formed in different dynamical environments and to measure the degree to which eccentricity-enhancing mechanisms affect these systems. Stellar obliquity, the mutual inclination of a planet’s orbital plane with the star’s spin axis, probes both primordial misalignments between the star and the natal disk from which planets are born as well as dynamical processes that introduce misalignments. Whereas there are extensive studies on the obliquities of close-in (< 1 au) exoplanets, very few measurements have been made for wide-separation giant planets. However, stellar obliquity measurements for this population can be made for the first time by combining archival high-resolution spectra, TESS photometry, and optical interferometry orbital monitoring. Close-in planets with >10-day orbital periods planets have low obliquities, so we nominally expect wide-separation planets to be the same. However, observations of protoplanetary disks show many cases where their outer disk may be misaligned to the inner disk and predict high stellar obliquities. Our proposed research will bridge these two observations. Lastly, the orbital monitoring proposed in this work will lead to dynamical measurements of these young exoplanets’ masses, a key parameter that is otherwise model-dependent. With the improved orbital constraints in this proposed work, we will measure masses for most directly imaged exoplanets by either using radial velocity or astrometric measurements of the host star, or by measuring planet-planet interactions in multi-planet systems. Since these planets are still young enough to bear the signatures of the planet formation process in their luminosities, comparing these dynamical masses and literature luminositi
Effective start/end date1/1/2312/31/25


  • NASA Goddard Space Flight Center (80NSSC23K0280)


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