Research: Measuring Stellar Spin Orientation
The spin orientation of a star projected on the sky can be measured with high-resolution spectroscopy using different spin-slit alignments. Like the Doppler shift from rotation, light coming from different points of the star (as an extended object) is shifted according its distribution along the dispersion direction of a spectrograph. The summed shift depends on the alignment of the spin orientation and the dispersion (or slit) axis of a spectrograph. Different spin-slit alignments realized by changing the derotator position angle produce different wavelength shifts and therefore different line broadening. By measuring line width deviations from identically observed spectra beside different position angles the spin-slit alignment can be concluded. Following most theories of planet formation the star and its planets have been formed conserving angular momentum from the same initial gas cloud. Without external torque this leads to a parallel alignment of orbital angular momentum of planets and the host star's spin. In our solar system this is mostly true but has not yet been proven for other planet systems (except for individual cases).
- Hayek, W., Wiesendahl, U., Christlieb, N., Eriksson, K., Korn, A. J., Barklem, P. S., Hill, V., Beers, T. C., Farouqi, K., Pfeiffer, B., Kratz, K.-L. (2009) The Hamburg/ESO R-process enhanced star survey (HERES). IV. Detailed abundance analysis and age dating of the strongly r-process enhanced stars CS 29491-069 and HE 1219-0312», A&A, Vol. 504, p. 511