Harvard Astronomy 201b

Special Topics

In Uncategorized on April 26, 2011 at 1:25 pm

According to our end of class survey, here are topics that might warrant (more) discussion/inclusion in a future version of AY201b…

Kolmogorov & Burgers Turbulence
“Kolmogorov” turbulence refers to turbulence in an incompressible medium.  “Burgers turbulence” refers to turbulence in a compressible medium (cf. Burgers equation).
Example of use: “Kolmogorov-Burgers Model of Star-forming Turbulence”, Boldorev 2002.

Dissociative Recombination
A process where a positive molecular ion recombines with an electron, and as a result, the neutral molecule dissociates.  Dissociative recombination is important in determining the chemical composition of the molecular interstellar medium, as it easily changes the balance amongst molecular species.
Typical example of dissociative recombination: CH_3^+ + e^- \rightarrow CH_2 + H

X-wind
The model of Frank Shu et al. for the formation of stars like the Sun.

Fig. 3 of Shang 2007 (reference below). Schematic drawing of a generalized picture of the X-wind. The deadzone is opened probably by continuous magnetic activities that result in reconnection events near the magnetic “Y” points and the current sheets. Adapted from Fig. 1 in Shu et al. (1997)

Recent Reference (and source of figure above): “Jets and Molecular Outflows from Herbig-Haro Objects,” Shang 2007.
Use in meteoritics: The X-wind model offers one explanation for the origin and nature of the chondritic meteorites found in our Solar System.

And, here are some topics that we’re betting will become (even) more important in the coming decade (in order of decreasing spatial scale)…

  • 21-cm tomography of the Early Universe
  • Magnetic fields in the IGM
  • Improved Extragalactic Star-Formation “Prescriptions” (e.g. Kennicutt-Schmidt), based on our understanding of the process near-er by
  • The role of magnetic fields in the low-density ISM (see WISE images…)
  • Numerical Models of star-forming regions that include ALL of these: gravity, heating/cooling, chemistry, radiative transfer, and magnetic fields.
  • AMR Simulations spanning pc to AU (star formation to planet formation)
  • Dense core “fragmentation”
  • The role of chemistry in core and planet formation
  • Time evolution of disk/planet formation (accretion, planet buildup, planet migration)
  • The relationship between planetary atmospheres and their formation environment
  • Laboratory measurements of the low-density, low-gravity, behavior of gases & solids (dust)
  • More…
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