New method reveals atmosphere on 'Hot Jupiter' (+video)
Using a ground-based telescope to probe exoplanet atmospheres, which were visible only when illuminated by stars, scientists say they hope to study much cooler planets.
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Seeing the planet's light directly also enabled the astronomers to measure the angle of the planet's orbit, helping them deduce its mass — six times that of Jupiter's — accurately for the first time.Skip to next paragraph
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"The new VLT observations solve the 15-year-old problem of the mass of Tau Boötis b. And the new technique also means that we can now study the atmospheres of exoplanets that don't transit their stars, as well as measuring their masses accurately, which was impossible before," Snellen said. "This is a big step forward."
The spectra also yielded details about the temperature of the exoplanet's atmosphere at different altitudes. Surprisingly, they found the planet's atmosphere seems to be cooler higher up, the opposite of what is seen with other hot Jupiters.
Earth's atmosphere is cooler at higher altitudes, the closer air gets to the frigid depths of space. Hot Jupiters, on the other hand, typically have atmospheres that are warmer farther up, perhaps due to gases present in their higher layers, such as titanium oxide.
Tau Boötis is a star very high in ultraviolet activity, radiation that may destroy these heat-absorbing gases and give Tau Boötis b an atmosphere with temperature features more like Earth's, researchers said.
The researchers focused on the spectrum of carbon monoxide, which is expected to be the second-most common gas in the atmospheres of hot Jupiters, after hydrogen. Unlike hydrogen, carbon monoxide has very strong and observable infrared spectral features. Future research can concentrate on other common gases in hot Jupiter atmospheres, such as water vapor and methane.
"Our method shows that exoplanet atmospheres can be very well studied using ground-based telescopes," Snellen said. Although Tau Boötis b is much too hot for any life, "possibly in the future we can extend this method to study much cooler planets like the Earth."
The scientists detailed their findings in the June 28 issue of the journal Nature.
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