Back to Volume
Paper: Imaging Extra-solar Systems from the Ground: The MMT and LBT Nulling Interferometers
Volume: 194, Working on the Fringe: Optical and IR Interferometry from Ground and Space
Page: 401
Authors: Hinz, P. M.; Angel, J. R. P.; Woolf, N. J.; Hoffmann, W. F.; McCarthy, D. W., Jr.
Abstract: Nulling interferometry is a key technique for imaging nearby star systems. We first demonstrated this technique with two 1.8 m mirrors of the now historic Multiple Mirror Telescope(MMT). The 5 m baseline allowed us to detect material 0.2 arcsec from a star at 10 microns. We are currently building a nulling instrument which will use two sections of the 6.5 m MMT for cancellation in a similar manner. Improved suppression relies on accurate control of the wavefronts with the MMT adaptive optics system. The AO system will be combined with an internal common-path phase-sensing system to suppress all but 10-4 of the stellar flux. This level of cancellation, combined with cryogenically-cooled optics, will allow us to detect zodiacal emission down to the milliJansky-level at 11 microns, 1000 times fainter than the Β Pictoris dust cloud. At 4 microns the instrument could detect planets from 20 Jupiter masses at 5 Gyr down to 1 Jupiter mass at 0.5 Gyr. The Large Binocular Telescope (LBT) will be an extremely efficient nulling interferometer. The two 8.4 m telescopes on a common mount, with deformable secondary mirrors for atmospheric correction, permit cryogenic beam combining after only three warm reflections. The modest baseline (14.4 m) allows suppression greater than 104 for nearby stars. The LBT will be sensitive to solar-level zodiacal emissiom 0.8 AU, at 11 microns, from a star at 10 pc. At 4 microns a planet the size of Jupiter, and 1 Gyr old, could be detected as close in as 0.3 AU. The enclosure, telescope structure and mirrors are all now under construction, and operation with both telescopes is projected for 2003.
Back to Volume