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Examples of LBT Science
Cosmology:
The study of phenomena at early epochs in the expansion of the Universe has been a major driver for astronomy since
early in this century. Slipher and Hubble first discovered the expansion and Einstein, Friedman, Lemaitre and de Sitter
interpreted it in terms of General Relativity. Indeed the Palomar 200-inch telescope was originally built to address
this problem and to determine the value of Hubble's constant (the proportionality between distance and velocity which
determines the age of the universe) and of the deceleration parameter (which measures the amount of matter or energy in
the universe). This goal was not realized because the galaxies were found to manifest substantial evolution in their
properties - an important discovery in itself. The "Palomar generation" of telescopes also led to the discovery of
quasars, the demonstration that the luminous material in the universe is not uniformly distributed even on scales as
large as several hundred million light-years, and that most of the material in the Universe could not be observed directly
(the problem of the "missing mass"). Also connected with these questions is the problem of the origin of the chemical
elements which, apart from hydrogen and helium, were formed almost entirely after matter began to condense into discrete
objects such as galaxies and stars. This latter process was already well advanced by the earliest epochs accessible to
current telescopes.
The LBT will play a major role in solving these problems, which in essence address the questions of how the material
content of the universe evolved from the postulated uniform distribution of the "hot big bang" to the current distribution
of galaxies, stars and planets of composition capable of supporting life. The stage was set at such early epochs that the
important processes are beyond the reach of current telescopes. In its wide field mode the LBT will permit the identification
of galaxies in the process of formation and its multifiber spectroscopy mode will allow analysis of their composition and
radial motion. The development of the "cluster and void" distribution of present day galaxies can then be documented and will
in turn provide insight into the nature of the "missing matter" which determines this evolution through its gravitational
effects. The results may have important implications for particle physics as well as cosmology. The high spatial resolution
capability will permit study of galaxy morphology and hence of the way galaxies form and the role of rotation in the process.
This capability will also permit study of the structure of galaxy nuclei and the giant black holes which seem to power the
quasars and radio sources.
Star and Planet Formation:
Observations with existing telescopes have shown that star (and presumably planet) formation is a continuing process within
dense interstellar clouds in our own and other galaxies. However, very little is known about the nature of the process,
especially the role of angular momentum, magnetic fields and initial turbulence on fragmentation (the final mass spectrum),
the formation of pre-planetary disks, and the formation of binary stars. The difficulties arise both because of the obscuration
of visible light by interstellar dust in star forming regions and because, during the stages of interest, the condensations are
sufficiently cool that they are quite faint and radiate mainly in the infrared, where the resolution and sensitivity of existing
telescopes is simply too low to solve the problems. The LBT will provide almost an order of magnitude (factor 10) gain in both
quantities and should permit major advances to be made. Some examples are given below:
Presence of low mass stars and substellar objects in star forming regions set important observational constraints on the mechanisms
for fragmentation of interstellar clouds and the accretion processes leading to star formation. Searches for these objects have been
frustrated by their intrinsically low luminosity and low surface temperatures. However, recent infrared imaging has revealed possible
members of young, embedded clusters that appear to be very low mass stars or brown dwarfs. Such observations begin to fill in the
missing link between stars and planets and also bear on the missing mass problem. These faint sources are currently beyond the limit
of infrared spectroscopy, which is required to establish conclusively their nature. The large aperture of the LBT together with the
improved image quality afforded by adaptive optics will allow, in the nearest embedded clusters, study of these faint sources.
Very young, solar mass stars often appear to be surrounded by a disk of gas and dust that may eventually evolve into a planetary system.
The mid-infrared emission of this disk dominates the output of the system for the first few million years, but then fades as the material
is expelled by stellar winds (and possibly partially condenses into planets). Recent HST imaging in the Orion nebula has confirmed the
existence of a few such disks, but most such systems are so rich of dust that they are only accessible in the near and mid infrared.
There is an urgent need for high spatial resolution images of these disks in the infrared. The closest embedded cluster suitable for such
studies is the Rho Ophiuchi cloud, where the diffraction limit of the LBT is such as to permit observations of great scientific interest.
Several other isolated, very young systems that also show evidence for preplanetary disks become accessible to study by the LBT. Thus, the
LBT is capable of resolving preplanetary disks in the first stages of evolution, and on a scale that would probe the subsequent formation
of planetary systems similar to the solar system.
The Direct Detection of Planets Orbiting Nearby Stars:
One of the long standing questions in astronomy has been whether planets exist around other stars. Since 1995 using indirect methods (Doppler
velocity techniques) astronomers have detected 17 cases of planetary systems around other stars. The next step is to make direct detections,
i.e., to obtain images of these planets as the orbit their parent stars. Thus far, direct observations of planets have been impossible because
of the presence of the very bright stellar image blurred by atmospheric "seeing". Since such a Jupiter-like planet would be roughly a billion
times fainter than the star, it would be impossible to detect using traditional techniques.
The LBT, equipped with adaptive optics (atmospheric blurring compensation) and fully exploiting the expected superb quality of its mirror surface
(already achieved in 3.5-m mirrors), will permit formation of images of sufficient sharpness (diffraction-limited) that the planet could be
detected against only a low surface brightness halo of residual scattered light. In this manner, a Jupiter-like planet could be detected, if
present, around some fifty of the nearest stars. The interferometric mode will enhance the planet/background contrast even further, thus increasing
the number of candidate stars and the sensitivity of the survey. The direct detection of such a planet would surely be counted as one of the major
steps forward in determining the likelihood of life existing elsewhere in the Universe and in understanding our place in it.