The birth of planets
Planets are born in the circumstellar disks, consisting of gas and dust grains of various sizes, which form around young stars. Observations made with high-resolution radio telescopes show that such disks can be highly structured, appearing as psychedelic patterns of bright concentric zones, separated by darker gaps. Astrophysicist Professor Barbara Ercolano at LMU’s Astronomical Observatory investigates the properties and processes that enable a subset of these disks to become nurseries for the formation of planets. How exactly do the initially microscopic specks of dust coalesce into ever larger grains, pebbles, rocks, and the kilometer-sized planetesimals that can ultimately grow into the plethora of planets that have already been discovered? Indeed, it is estimated that our galaxy alone hosts billions of planets. Ercolano is also interested in characterizing the conditions that permit the development of Earth-like planets. According to Ercolano, who specializes in Computational Astrophysics, one of the most significant forces that shape the evolution of circumstellar disks is the phenomenon known as photoevaporation: Highly energetic X- and far ultraviolet radiation emitted by the central star essentially burns holes in the disk, heating the gas and setting up pressure gradients that drive it outwards. The gaps created by photoevaporation can serve as niches for the growth of young planets. On the other hand, photoevaporation can promote the complete dissipation of the material in the disk -- which, of course, puts an end to planet formation. In fact, according to Barbara Ercolano’s latest work, that is the fate which awaits the disk encircling TW Hydrae, a young star that lies only 175 light-years from Earth.
The death of a planet nursery? (09.16.2016)