Astronomers have now found over 400 planets orbiting other stars. Virtually all of these exciting discoveries were made by indirect means, inferring the presence of a planet by the gravitational tug and pull it makes on its star. Only a handful of planets have actually been "seen" through astronomers' telescopes. But significant advances are being made in the field of adaptive optics, which corrects for the distortion of images introduced as light from the distant solar systems passes through the earth's atmosphere; and new capabilities to mask the star's light to help see the much fainter companions are also under development. Astronomers are hopeful that we will soon actually be able to identify planets and characterize their chemistry by direct observation of the planets while masking the light from the star. Dr. Ben Oppenheimer of the American Museum of Natural History is leading an effort to develop techniques and instrumentation that will work with advances in adaptive optics to make these observations possible. He will use the new adaptive optics system at the Palomar Observatory 200-inch Hale telescope to conduct his investigations. His work is supported by NSF's Major Research Instrumentation program through the Division of Astronomical Sciences.
This grant was used to conduct significant upgrades and improvements to an existing astronomical instrument called Project 1640. Project 1640 is a unique camera that enables imaging of planets orbiting stars other than the Sun. It works by blocking the starlight with an optical device called a coronagraph. This removes the majority of starlight from the beam which is then directed to a "integral field spectrograph" or IFS. The IFS takes images of the region around the star at 32 different wavelengths of light simultaneously. Those images are then used to detect faint objects up to 10 million times fainter than the star at the center of the image. Since there are images made at 32 different wavelengths, the spectrum of any object in the field of view can be derived. A spectrum is simply how bright something is as a function of wavelength. Spectra are the key to understanding the chemistry and physics of planets because different molecules and chemical species absorb or emit light at specific and known wavelengths. Thus by extracting the spectrum of a planet in our field of view we can, for example, detect the presence of gasses such as methane, water, and carbon dioxide. This grant provided funds for replacing the imaging detector in the IFS and support for the scientists to do the work to upgrade this detector, which is a very complex and delicate device requiring electrical engineering and significant software development as well as modification of some of the mounts in the IFS. The result is a system that is currently the most sensitive exoplanet imaging device in the world. It provides a new human capability to conduct complete reconnaissance of other solar systems, including the chemical composition, temperature and orbital characteristics of those planets. Project 1640 is currently involved in a 3-year observing campaign at the Palomar Hale Telescope.
