“This is the sharpest spectrum ever obtained of an extrasolar planet,” said co-author Bruce Macintosh, an astronomer at LLNL. “This shows the power of directly imaging a planetary system—the exquisite resolution afforded by these new observations has allowed us to really begin to probe planet formation.”
All four planets are more massive than any in our Solar System, with masses three to seven times that of Jupiter. Their orbits are similarly large when compared to our system. The system is believed to be young, of the order of 30 million years. HR 8799c orbits 40 times farther from its parent star than the Earth orbits from the Sun; in our Solar System that would put it beyond the realm of Neptune.
The team analyzed the distant giant’s atmosphere using a high-resolution imaging spectrograph called OSIRIS. Just as Keck’s adaptive optics technology gives astronomers a sharp image of HR 8799c, OSIRIS enables an extremely detailed analysis of the spectrum of the light from the planet—much more detailed than ever before—and allows astronomers to separate the star’s light from the planet’s. This in turn provides a more detailed understanding of the composition of the gas giant’s atmosphere.
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