Class description: In this "shotgun seminar", students will calculate order of magnitude estimates of astrophysical interest, such as the size of an active galactic nucleus, the height of tides on the earth, the lifetime of radiatively supportive star. The goal is to acquire broad knowledge of astrophysical phenomena and the ability to estimate quantities so that astrophysical scales become intutive.

Prerequisites: Good understanding of astrophysics.

Grades: Pass or fail.

References: to be listed

Problem sets:
Week 1 (Yoo): WIMP Miracle! pdf

Week 2 (Saha): From the LIGO signals, read off the mass of the merging binary system! pdf

Week 3 (Yoo): Probing the magnetic field with CMB in cosmology pdf

Week 4 (Feldmann): Jeans equation and estimates of the local dark matter density pdf

Week 5 (Helled): Asteroids
(a) How high can a mountain be on Earth? The Moon? An asteroid? The compressibility for granite is about 30,000 pounds per square inch (2 x 10^8 N/m^2).
(b) How large must an asteroid be before its self-gravity makes it round?

Week 6 Easter break

Week 7 (Saha): Space elevator
Estimate the minimum tensile strength needed in a space elevator. Express it in two ways:
(a) in terms of easily-remembered quantities like the Earth's radius, g, length of a day, etc., and
(b) as an equivalent sound speed. [Recall that sound speed relates to elastic constants and density.]
Are there any materials that are strong enough?

Week 8 (Feldmann): Measuring the Hubble parameter from the strong gravitational lensing system pdf

Week 9 (Saha): SN 1006
SN 1006 is the brightest historically-recorded supernova. Since the year 1006, the remnant has expanded to a radius of 10 parsecs, because of the kinetic energy of the explosion. The value of the latter would be roughly one foe.
Using dimensional analysis and the above numbers, estimate the local density of the interstellar medium in that region. For a hint, see

Week 10 (Helled): Stellar mass scaling relation: pdf

Week 11 Ascension break

Week 12 (Yoo): 21cm signals from redshift 17 the EDGES observation! pdf

Week 13 (Feldmann): Metal enrichment of galaxies pdf

Week 14 (Helled): Compute the coefficient J2 of the gravitational potentialo of a planetpdf