October 12, 2011 — University of Virginia astrophysicist Fred Hearty is a member of a team designing and building a new state-of-the-art instrument – a precision spectrograph for finding planets in habitable zones around nearby stars – that is being developed for the Hobby-Eberly Telescope at the McDonald Observatory in East Texas.
The overall project is led by astronomer Suvrath Mahadevan at Pennsylvania State University, the recipient of a new $3.3 million grant from the National Science Foundation.
The Habitable Zone Planet Finder is designed to help astronomers detect planets as small as a few times the size of Earth, orbiting their stars, that would likely allow the formation of liquid water, believed essential for the development of living matter.
The instrument is a high-resolution, infrared spectrograph that will be able to compare the spectrum of starlight in observations taken at different times to detect minute wobbles of nearby stars that would be caused by the gravity of orbiting planets. An infrared spectrograph observes light at wavelengths longer than visible light, which is where the target stars release most of their energy.
The Habitable Zone Planet Finder will be about the size of an SUV and weigh more than two tons, yet will be operated for months to years with ultra-stable optics – stable to within a few thousandths of a degree Celsius. This is important because even small temperature changes would otherwise mask the minuscule wobbles.
U.Va. is contributing systems engineering and project management expertise to build the enclosure for the spectrograph, based on the design used for APOGEE, another major astronomy project led by U.Va. This enclosure will produce a state-of-the-art, ultra-stable instrument internal environment so essential for precision measurements.
"The method being developed has already been used in other projects to detect about 600 planets, though typically they are giant hot gas planets larger than Jupiter," said Hearty, an astronomy research scientist in the College of Arts & Sciences. "Our goal is to push this technology into the infrared region so we can find nearby habitable planets."
The Habitable Zone Planet Finder will observe small, cool stars – the most numerous types of stars in the Milky Way, according to co-principal investigator Lawrence Ramsey, a Penn State astronomer and astrophysicist.
"These stars, which have temperatures far below that of the sun, radiate very little of their energy in the visible part of the spectrum, so we must create an instrument that can capture the infrared part of the spectrum – where the unaided human eye cannot see but where these stars are brightest," he said.
Those stars offer the best opportunity for finding planets with solid surfaces in the so-called "Habitable Zone" around nearby stars – the range of distances from a star within which temperatures might be right for liquid water.
The instrument will take three years to build at Penn State, and then will be shipped to the Hobby-Eberly Telescope to begin its multi-year quest for new worlds, during which it will survey more than 100 nearby stars for the telltale wobble effect caused by orbiting planets. Once a wobble is detected on a star's motion, astronomers can infer the surface temperature and mass of the planet or planets orbiting it.
"The exciting thing is that we will be able to identify the nearest-to-Earth habitable planets a few years from now," Hearty said. "Scientifically, these planets will provide the best opportunity to identify signatures of life; the knowledge that there are living organisms on a not-so-far-away planet will answer a key question about our origins, while it gives our collective imagination something to ponder."
In addition to Hearty, the Hobby-Eberly Telescope development and science team includes several Penn State researchers, as well as scientists from the University of Texas.