High contrast imaging of extra-solar planets and brown dwarfs. Prof.
Ge's group and his collaborators, at Princeton University, Harvard-Smithsonian
Center for Astrophysics and Ball Aerospace Technology Inc. are developing
new coronagraph techniques for the NASA Terrestrial Planet Finder mission,
to be launched in 2015. They have successfully demonstrated the feasibility
of a shaped pupil coronagraph for high contrast imaging in the lab, as
well as, at the astronomical telescope. In the lab, they have reached ~ 10-6 contrast at ~ 5 times diffraction-limited
Airy disk size. At the Mt. Wilson 100inch telescope with a high order adaptive
optics system, they have reached ~ 10-4 at the ~ 10 times diffraction-limited Airy disk size. They have successfully detected faint companions around nearby stars using this new high contrast
imaging technique. They are working on developing new techniques for further
improvement in image contrast. Their goal is to reach ~ 10-10
contrast to allow TPF to detect Earth-like planets in space in next decade. Prof. Ge's group is also taking advantage of the new high contrast
imaging techniques to search for brown dwarfs and giant planets around
nearby stars. To date, they have detected two transition objects, and a
brown dwarf candidates.
of protoplanets and young stellar objects . Prof. Ge and his research
group are working on detecting protoplanets using silicon immersion gratings
they developed at Penn State nanofabrication
facility. Detection of dynamic gas gaps formed by protoplanets in planetary
disks is perhaps the most feasible way for detecting planet formation.
However, it requires a spectral resolution of at least R = 100,000 at 4.6
micron. The silicon immersion gratings, due to their more than 3x dispersing
power than conventional gratings, make this high resolution IR spectroscopy
possible at large ground-based telescopes. A silicon immersion grating
with a resolving power of R ~ 120,000 at 4.6 micron is being manufactured
and will be available for observing in 2003. In demonstration observations
with a prototype silicon grism, they detected a rotating disk with a FWHM
of 550 km/s around a Be star, BD +65 1638 (a possible progenitor of a fast rotating Be star),
for the first time.
Emission lines from the CO 4.6 micron band and other molecular bands formed in the dynamic gaps among all ~ 300 T Tauri stars out to the distance of Taurus (d = 140 pc) will be searched. This will form a sufficient statistical sample for comparison with results from precision Doppler velocity surveys. Since both the Doppler and silicon immersion grating techniques probe similar orbital regions around stars, the results from these surveys will be used to investigate if orbital migration and dynamical scattering play a significant role in planet formation and evolution.
transit experiments. The upcoming Venus transits across the solar disk
are rare events, occurring in pairs less than once per century. Prof. Ge's
group and his collaborators, Dr. Sara Seager and her group at the Carnegie
Institute of Washington, are working on preparing a 3-D imaging spectrograph
for capturing transit spectra. This data will be used for testing the feasibility
of detection of terrestrial planet transmission spectra within the signal
of a non-spatially resolved star for future space missions. The eventual
detection and characterization of extra-solar terrestrial planets, especially
those with signs of atmospheric modification by life, will have a huge
impact on science and society.
Extra-solar planets around pulsars . Prof.
Alex Wolszczan and his research group are leading this effort. Penn
State's Pulsar group was the first in detecting extra-solar planets.
Extra-solar planets around white dwarfs
Steinn Sigurdsson and his research group have developed a theoretical
model for planet formation and evolution around white dwarfs.