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A study combining observations from NASA’s Hubble and Spitzer space telescopes reveals that the distant planet HAT-P-26b has a primitive atmosphere composed almost entirely of hydrogen and helium. Located about 437 light years away, HAT-P-26b orbits a star roughly twice as old as the sun.
The analysis is one of the most detailed studies to date of a “warm Neptune,” or a planet that is Neptune-sized and close to its star. The researchers determined that HAT-P-26b’s atmosphere is relatively clear of clouds and has a strong water signature, although the planet is not a water world. This is the best measurement of water to date on an exoplanet of this size.
The discovery of an atmosphere with this composition on this exoplanet has implications for how scientists think about the birth and development of planetary systems. Compared to Neptune and Uranus, the planets in our solar system with about the same mass, HAT-P-26b likely formed either closer to its host star or later in the development of its planetary system, or both.
“Astronomers have just begun to investigate the atmospheres of these distant Neptune-mass planets, and almost right away, we found an example that goes against the trend in our solar system,” said Hannah Wakeford, a postdoctoral researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study published in the May 12, 2017, issue of Science. “This kind of unexpected result is why I really love exploring the atmospheres of alien planets.”
To study HAT-P-26b’s atmosphere, the researchers used data from transits— occasions when the planet passed in front of its host star. During a transit, a fraction of the starlight gets filtered through the planet’s atmosphere, which absorbs some wavelengths of light but not others. By looking at how the signatures of the starlight change as a result of this filtering, researchers can work backward to figure out the chemical composition of the atmosphere.
In this case, the team pooled data from four transits measured by Hubble and two seen by Spitzer. Together, those observations covered a wide range of wavelengths from yellow light through the near-infrared region.
www.nasa.gov
The analysis is one of the most detailed studies to date of a “warm Neptune,” or a planet that is Neptune-sized and close to its star. The researchers determined that HAT-P-26b’s atmosphere is relatively clear of clouds and has a strong water signature, although the planet is not a water world. This is the best measurement of water to date on an exoplanet of this size.
The discovery of an atmosphere with this composition on this exoplanet has implications for how scientists think about the birth and development of planetary systems. Compared to Neptune and Uranus, the planets in our solar system with about the same mass, HAT-P-26b likely formed either closer to its host star or later in the development of its planetary system, or both.
“Astronomers have just begun to investigate the atmospheres of these distant Neptune-mass planets, and almost right away, we found an example that goes against the trend in our solar system,” said Hannah Wakeford, a postdoctoral researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study published in the May 12, 2017, issue of Science. “This kind of unexpected result is why I really love exploring the atmospheres of alien planets.”
To study HAT-P-26b’s atmosphere, the researchers used data from transits— occasions when the planet passed in front of its host star. During a transit, a fraction of the starlight gets filtered through the planet’s atmosphere, which absorbs some wavelengths of light but not others. By looking at how the signatures of the starlight change as a result of this filtering, researchers can work backward to figure out the chemical composition of the atmosphere.
In this case, the team pooled data from four transits measured by Hubble and two seen by Spitzer. Together, those observations covered a wide range of wavelengths from yellow light through the near-infrared region.
Study Finds Primitive Atmosphere Around ‘Warm Neptune'
By combining observations from NASA's Hubble and Spitzer space telescopes, a new study has found that the planet HAT-P-26b has an atmosphere composed almost entirely of hydrogen and helium, with a relatively cloudless sky.
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