Interferometry: Combining light from the two sides of the Observatory
LBT Interferometer (LBTI): The Large Binocular Telescope Interferometer is a system which includes "nulling interferometry" or a nulling mode - which will directly image planets in other solar systems. A key project for the program is to survey nearby stars for dust and planet disks down to levels which may obscure detection of Earth-like planets. Nulling Interferometry (http://lbti.as.arizona.edu/LBTI-Main/Science_Possiblilities.html) suppresses the light from a central star while enhancing light from orbiting dust and planets. To achieve this, the LBTI is intended to study the infrared portion of the spectrum in which dust and planets would glow the most strongly. While the LBT has unprecedented resolving power, it is still not capable of finding Earth-sized planets. The smallest planets the telescope can expect to discover are around two times the mass of Jupiter. Smaller planets would likely not emit strongly enough and be lost in the glare from their parent star. Young planets a billion years old (or less) are very bright in the infrared. These self luminous planets will be readily detectable down to 2 Jupiter masses.
Rear view of LBT showing position of LBTI (in blue) http://lbti.as.arizona.edu/LBTI-Main/Project.html
The characterization of habitable environments is the primary scientific goal of the LBTI project. LBTI will accomplish this in two ways. First, by detecting zodiacal dust around a star it will be identifying which stars have planetessimals (planet-forming objects) in the habitable zone, and thus might have larger, rocky planets such as Earth, as well. Secondly, by detecting Jupiter-like planets and characterizing their orbits, LBTI will be identifying which stars have gas giants similar to our own and determining whether these planets provide a dynamically stable or unstable habitable zone about their star. Thus the LBTI observations naturally lay the groundwork for future searches for other planetary systems and Earth-like planets in particular. The system will also be able to build on the heritage of the Spitzer and Hubble Space Telescopes that have identified outer debris disks similar to our Kuiper belt which may provide good indications of other solar systems.
The large brightness difference between a planet and its star at close angular separation requires innovative techniques to avoid confusion of star and planet light. Two leading techniques for possible use on future space missions are being tested out using LBTI. Nulling interferometry is being developed for the zodiacal dust detection at 10 micrometer. For detection of giant planets a coronagraphic approach is being developed to suppress diffracted light at only several resolution elements away from the star. This development is the work of students, astronomers and engineers, who are all developing the requisite skills to improve the state-of-the art for high contrast imaging: the crucial technique for any future extrasolar planet mission.
By identifying Jupiter-like planets and zodiacal dust, LBTI will be finding the signposts for habitable environments around nearby stars that provide natural follow up targets for the James Webb Space Telescope or other future NASA mission targeted at extrasolar planets.
The instrument was delivered and installed in July 2008 and re-installed in 2009-10 (after the first adaptive optics secondary was commissioned). Scientific operations will start sometime in early 2011.The instrument is comprised of a central beam combiner that directs the optical beam from each primary mirror into the Nulling Imaging Camera. All the optics are cooled to 100 Kelvin or below to reduce thermal emissions. Movie of installation of LBTI: http://lbti.as.arizona.edu/LBTI-Main/Project_files/LBTI_Lift.mov
The combination of super high spatial resolution and wavelength coverage (3-13µm) make the LBTI a powerful tool for studying exo-planetary systems as well as more general astrophysical studies ranging from comets in our own solar system to active galactic nuclei at moderate redshifts.
On larger scales, the LBTI will be suited for studying of star-formation in the Milky Way, as well as other, nearby galaxies. Further out, the instrument can be employed to study Ultra Luminous Infrared Galaxies (ULRIGs) and Active Galactic Nuceli (AGN). (For overview of upcoming research, see http://lbti.as.arizona.edu/LBTI-Main/Science_files/LBTI-white-paper-081218.pdf)
The LBTI is comprised of:
1) a Universal Beam Combiner (UBC), which combines the optical beam from the two telescope primaries into a single focus
2) a rigid interface structure (ISS)
3) the Nulling Infrared Camera (NIC), which is the main science camera being developed for use with the LBTI with a 40 x 60 arc sec field of view:
Universal Beam Combiner assembly and Nulling and Imaging Camera http://lbti.as.arizona.edu/LBTI-Main/NIC.html
4) Wave Front Sensor units (wLBTI)
5)The Control Software (CS)
6) the support hardware and electronics