Astronomers Conduct First Remote Reconnaissance of Another Planetary System

Researchers have conducted a remote reconnaissance of a distant planetary system with a new telescope imaging system that sifts through the blinding light of stars. Using a suite of high-tech instrumentation and software called Project 1640, the scientists collected the first chemical fingerprints, or spectra, of this system’s four red exoplanets, which orbit a star 128 light years away from Earth.

A detailed description of the planets — showing how drastically different they are from the known worlds in the universe — was accepted Friday for publication in The Astrophysical Journal.

“An image is worth a thousand words, but a spectrum is worth a million,” said lead author Ben R. Oppenheimer, associate curator and chair of the Astrophysics Department at the American Museum of Natural History,according to Science Daily.

Oppenheimer is the principal investigator for Project 1640, which uses the Hale telescope at the Palomar Observatory in California. The project involves researchers from the California Institute of Technology, NASA’s Jet Propulsion Laboratory, Cambridge University, New York University, and the Space Telescope Science Institute, in addition to Oppenheimer’s team at the Museum.

The planets surrounding the star of this study, HR 8799, have been imaged in the past. But except for a partial measurement of the outermost planet in the system, the star’s bright light overwhelmed previous attempts to study the planets with spectroscopy, a technique that splits the light from an object into its component colors — as a prism spreads sunlight into a rainbow. Because every chemical, such as carbon dioxide, methane, or water, has a unique light signature in the spectrum, this technique is able to reveal the chemical composition of a planet’s atmosphere.

“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,” said Charles Beichman, executive director of the NASA Exoplanet Science Institute at the California Institute of Technology. “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.”

With this system, the researchers are the first to determine the spectra of all four planets surrounding HR 8799. “It’s fantastic to nab the spectra of four planets in a single observation,” said co-author Gautam Vasisht, an astronomer at the Jet Propulsion Laboratory.

The results are “quite strange,” Oppenheimer said. “These warm, red planets are unlike any other known object in our universe. All four planets have different spectra, and all four are peculiar. The theorists have a lot of work to do now.”

Researchers are already collecting more data on this system to look for changes in the planets over time, as well as surveying other young stars. During its three-year survey at Palomar, which started in June 2012, Project 1640 aims to survey 200 stars within about 150 light years of our solar system.

“The variation in the spectra of the four planets is really intriguing,” said Didier Saumon, an astronomer at Los Alamos National Laboratory who was not involved in this study. “Perhaps this shouldn’t be too surprising, given that the four gaseous planets of the solar system are all different. The hundreds of known exoplanets have forced us to broaden our thinking, and this new data keeps pushing that envelope.”

M.W