Research

Three-Body Problem at High e = Simple Pendulum

Cool new results by Ygal Klein:
Three-body systems - three masses moving under their mutual gravitational attraction, such as the Earth-moon-sun system pose a long standing problem since the days of Newton. One of the recent realizations is that very close approaches of two of the bodies are rather common in such systems, whith the inner orbit approaching very high ellipticity (eccentricity approaching one). Ygal has now showed that for a large fraction of the relevant parameter space, the long term dynamics is mathematically equivalent to a simple pendulum and can be solved simply, and analytically, to an excellent approximation.

Paper I

Paper II

 

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Modeling the light from supernovae

 

Most of the information on supernovae comes from optical observations during the first weeks and months following the explosion. One of the challenges in understanding the explosions is to relate the observed features of the emitted light to the properties of the exploding star and the explosion mechanism. This is challenging due to the fact that the light can be absorbed and emitted by thousands of atomic transitions on its way out. We are working on detailed numerical radiation transfer calculations as well as analytic approximations in order to learn about the explosions from the observations. 

The equation in the image is a new and useful relation we recently found between the injection of energy Q(t) in the expanding material from radioactive decay and the total bolometric luminosity L(t) of supernovae. This equation is a direct result of conservation of energy with the multiplication by t exactly correcting for the adiabatic losses. This equation allows us to directly and robustly measure several global properties of the explosion, bypassing the complications of radiation transfer. 

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