March 13, 2013
New Imaging System Allows Astronomers To See Distant Planets
Brett Smith for redOrbit.com — Your Universe Online
Using a state-of-the-art telescopic imaging system, astronomers are now able to see planets that orbit distant stars, known as exoplanets, more easily and in greater detail, according to a report in the Astrophysical Journal.
Scientists gather information from distant planets via the light they radiate, referred to as their spectra, and previously, astronomers have only been able to analyze planets as they pass in front of, or transit, the stars they orbit.
However, a new imaging system, dubbed Project 1640, allows astronomers to measure direct spectra of planets that are not transiting.
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"We are now technically capable of obtaining spectra of giant planets in planetary systems like our own, improving on the close-in transiting planet studies done previously," said co-author Lynne Hillenbrand, professor of astronomy at the California Institute of Technology (Caltech).
The device, which is based in Caltech's Palomar Observatory, works by blocking the overwhelming light generated by the distant star to allow the faint specks of planetary light to be measured.
"It's like taking a single picture of the Empire State Building from an airplane that reveals the height of the building but also a bump on the sidewalk next to it that is as high as a couple of bacteria," said co-author Ben R. Oppenheimer, an astronomer at the American Museum of Natural History. "Furthermore, we've been able to do this over a range of wavelengths in order to make a spectrum."
Project 1640 has already enabled the team to simultaneously determine the spectra of all four of the planets around HR 8799, a solar system 129 light years from Earth, a feat that had never been done before.
"These warm, red planets are unlike any other known objects in our universe," Oppenheimer said. "All four planets have different spectra and all four are peculiar."
The new imaging system is also unique because the planets around HR 8799 are at about the same distance from that star as Jupiter, Saturn and Uranus are from our sun. The previously used transiting systems have only been able to take the spectra of planets with orbits about the length of Mercury's.
"Our young century has seen seminal advances in exoplanet science, but almost exclusively from indirect observations," said co-author Richard Dekany, an associate director for Caltech Optical Observatories. "Project 1640 has now added to this revolution the scientific gold standard: directly measured spectra of young giant planets. Our initial findings suggest each of these strange and wonderful giant planets may have a unique story to share."
These exoplanets appear to be unique because their spectra reveal a chemical imbalance in their atmosphere. The spectra of these exoplanets reveal they have either methane or ammonia alone, which is unusual because these two elements are typically seen together in extraterrestrial atmospheres.
"In the 19th century, it was thought impossible to know the composition of stars, but the invention of astronomical spectroscopy has revealed detailed information about nearby stars and distant galaxies," added co-author Charles Beichman, an executive director of the NASA Exoplanet Science Institute at Caltech.
"Now, with Project 1640, we are beginning to turn this tool to the investigation of neighboring exoplanets to learn about the composition, temperature, and other characteristics of their atmospheres."