The centers of most galaxies contain massive black holes surrounded by dense star clusters. The structure of these clusters determines the rate and properties of observable transient events, such as flares from tidally disrupted stars and gravitational-wave signals from stars spiraling into the black hole. Most estimates of these rates enforce spherical symmetry on the cluster.
View Article and Find Full Text PDFNumerous telescopes and techniques have been used to find and study extrasolar planets, but none has been more successful than NASA's Kepler space telescope. Kepler has discovered most of the known exoplanets, the smallest planets to orbit normal stars and the planets most likely to be similar to Earth. Most importantly, Kepler has provided us with our first look at the typical characteristics of planets and planetary systems for planets with sizes as small as, and orbits as large as, those of Earth.
View Article and Find Full Text PDFPhilos Trans A Math Phys Eng Sci
March 2005
If accretion onto massive black holes is the power source for active galaxies, then nearby galaxies should contain 'dead quasars': black holes that do not shine, either because they are starved for fuel or because they accrete with low radiative efficiency. This article briefly reviews the evidence that most inactive galaxies contain black holes at their centres, and how the local distribution of black holes is related to the population of active galaxies.
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