Primordial obliquities of brown dwarfs and super-Jupiters from fragmenting gravito-turbulent discs
Abstract
Super-Jupiters, brown dwarfs, and stars can form from the collapse of self-gravitating discs. Such discs are turbulent, with flocculent spiral arms accelerating gas to transonic speeds horizontally and vertically. Objects that fragment from gravito-turbulent discs should spin with a wide range of directions, reflecting the random orientations of their parent eddies. We show by direct numerical simulation that obliquities of newly collapsed fragments can range up to 45○. Subsequent collisions between fragments can further alter the obliquity distribution, up to 90○ or down to near-zero. The large obliquities of newly discovered super-Jupiters on wide orbits around young stars may be gravito-turbulent in origin. Obliquely spinning fragments are born on orbits that may be inclined relative to their parent discs by up to 20○, and gravitationally stir leftover material to many times the pre-fragmentation disc thickness.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- November 2021
- DOI:
- 10.1093/mnras/stab2429
- arXiv:
- arXiv:2105.12160
- Bibcode:
- 2021MNRAS.507.5187J
- Keywords:
-
- turbulence;
- planets and satellites: formation;
- protoplanetary discs;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 9 pages, 7 figures. Accepted to MNRAS