Search

The known extrasolar planets exhibit many interesting and surprising features—extremely short-period orbits, high-eccentricity orbits, mean-motion and secular resonances, etc.—and have dramatically expanded our appreciation of the diversity of possible planetary systems. In this review we summarize the orbital properties of extrasolar planets. One of the most remarkable features of extrasolar planets is their high eccentricities, far larger than seen in the solar system. We review theoretical explanations for large eccentricities and point out the successes and shortcomings of existing theories. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Coalescing massive black hole binaries are powerful emitters of gravitational waves, in the LISA sensitivity range for masses MBH ≈ 104–7 M⊙. According to hierarchical galaxy merger models, binary black holes should form frequently, and should be common in the cores of galaxies. The presence of massive black hole binaries has been invoked to explain a number of class properties of different types of galaxies, and in triggering various forms of activity. The search for such binary black holes is therefore of great interest for key topics in astrophysics ranging from galaxy formation to activity in galaxies. A number of phenomena were attributed to the presence of supermassive binary black holes, including X-shaped radio galaxies and double-double radio galaxies, helical radio-jets, periodicities in the lightcurves of blazars, (double-horned emission-line profiles), binary galaxies with radio-jet cores, binary quasars, and the X-ray active binary black hole at the center of the galaxy NGC 6240. Here, I review the observational evidence for the presence of supermassive binary black holes in galaxies, and the scenarios which have been discussed to explain these observations. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]