School of Astronomy (SoA) - Weekly Seminar

By: Mir Abbas Jalali (SUT)  

Wednesday / 27-June-2012 / 7-Tir-1391/ 2:00 PM

IPM Larak Building, School of Astronomy 

Address: Larak Garden, opposite Araj, Artesh Highway,Tehran, Iran
E-mail: astro(at)ipm.ir

Abstract

Debris disks around stars are planetesimal disks that cannot be observed directly, but are 
detectable through thermal emission of the dust formed in recent planetesimal collisions. 
We review the observed patterns of debris disks around young stars. They include lopsided 

rings and spirals, which are often ascribed to unseen planets. The most famous example

is the eccentric ring of Fomalhaut. We show that observed structures can alternatively arise 

due to density waves triggered by stellar encounter. Density waves that we find are slow 

oscillatory modes with very long life times. Structures formed by planets and density waves 

can be distinguished by long-term monitoring of pattern rotations. We argue that patterns 

rotating slower than 1 degree per decade are due to waves while the faster ones (with 

pattern speeds of 1 degrees per year) may be associated with planets. Our theory can 

be tested by future observations of ALMA and CCAT.