AAS 203rd Meeting, January 2004
Session 23 Quasars, Blazars and Jets
Oral, Monday, January 5, 2004, 10:00-11:30am, Centennial I/II

## [23.07] Photon Orbital Angular Momentum in Astrophysics

M. Harwit (Washington, DC and CRSR, Cornell University)

Observations of the orbital angular momentum of photons --- a property of electromagnetic radiation that has come to the fore in recent years --- have apparently never been attempted in astronomy. By now it is known from laboratory studies that, in addition to carrying spin angular momentum, individual photons can carry N >> 100 units of orbital angular momentum h/2\pi. After describing the effect and its origins, I will discuss how measurements of this property of photons may have applications in several areas of astrophysical interest. Among these are: i) searches probing rapidly spinning black holes, ii) analyses of different types of discontinuities along the line of sight to astronomical masers, and iii) probes for extraterrestrial communications (where the ability of individual photons to carry (1 + log2N) bits of information can provide significant economies). Since photons of any wavelength may be endowed with orbital angular momentum, some of these studies will best be carried out in the radio domain, while others will be better tackled at optical or higher frequencies. Much of my astronomical research is supported by NASA contracts.

Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.