Editor's Summary
20 January 2005
Star formation: evidence of mass
The rapidly spinning young star AB Doradus (AB Dor) is thought to have a low-mass companion star, detected as an astrometric 'wobble'. It has proved elusive — even to the Hubble Space Telescope — but now a new instrument built to image extrasolar planets shows what it can do by observing the faint companion. The high-contrast NACO SDI adaptive optics camera at the European Southern Observatory reveals the object, dubbed AB Dor C, to be of very low mass for a star (90 times that of Jupiter). It is 400 °C cooler and 2.5 times fainter than predicted by stellar models. This suggests that most known brown dwarfs and extrasolar planets are heavier than was thought, and the new findings will be important for the design of future cameras intended to find extrasolar planets. See the cover story for more on the search for new planets.
News and Views: Astronomy: Weighing the baby
Mass is the fundamental parameter in stellar astrophysics, but measuring mass is difficult, especially for young stars. A study of a youthful neighbour of the Sun provides insight into the accuracy of widely used calibrations.
I. Neill Reid
doi:10.1038/433207a
Letter: A dynamical calibration of the mass–luminosity relation at very low stellar masses and young ages
Laird M. Close, Rainer Lenzen, Jose C. Guirado, Eric L. Nielsen, Eric E. Mamajek, Wolfgang Brandner, Markus Hartung, Chris Lidman and Beth Biller
doi:10.1038/nature03225
