Astronomers map exoplanet atmosphere of super-Earth
Worlds without end: Using both the Hubble and Spitzer space telescopes, astronomers have characterized the atmosphere of an exoplanet with a mass between that of the Earth and Neptune.
Astronomers enlisted the combined multi-wavelength capabilities NASA’s Hubble snd Spitzer space telescopes to do a first-of-a-kind study of GJ 3470 b’s atmosphere. This was accomplished by measuring the absorption of starlight as the planet passed in front of its star (transit) and the loss of reflected light from the planet as it passed behind the star (eclipse). All totaled, the space telescopes observed 12 transits and 20 eclipses. The science of analyzing chemical fingerprints based on light is called “spectroscopy.”
“For the first time we have a spectroscopic signature of such a world,” said Benneke. But he is at a loss for classification: Should it be called a “super-Earth” or “sub-Neptune?” Or perhaps something else?
Fortuitously, the atmosphere of GJ 3470 b turned out to be mostly clear, with only thin hazes, enabling the scientists to probe deep into the atmosphere. “We expected an atmosphere strongly enriched in heavier elements like oxygen and carbon which are forming abundant water vapor and methane gas, similar to what we see on Neptune”, said Benneke. “Instead, we found an atmosphere that is so poor in heavy elements that its composition resembles the hydrogen/helium rich composition of the Sun.”
To me, our knowledge of exoplanets today is beginning to resemble our knowledge of the planets in the solar system c. 1950. The little data we have gives us a vague idea of what’s there, but there are so many gaps and uncertainties that no one should be confident about drawing any firm conclusions.
Worlds without end: Using both the Hubble and Spitzer space telescopes, astronomers have characterized the atmosphere of an exoplanet with a mass between that of the Earth and Neptune.
Astronomers enlisted the combined multi-wavelength capabilities NASA’s Hubble snd Spitzer space telescopes to do a first-of-a-kind study of GJ 3470 b’s atmosphere. This was accomplished by measuring the absorption of starlight as the planet passed in front of its star (transit) and the loss of reflected light from the planet as it passed behind the star (eclipse). All totaled, the space telescopes observed 12 transits and 20 eclipses. The science of analyzing chemical fingerprints based on light is called “spectroscopy.”
“For the first time we have a spectroscopic signature of such a world,” said Benneke. But he is at a loss for classification: Should it be called a “super-Earth” or “sub-Neptune?” Or perhaps something else?
Fortuitously, the atmosphere of GJ 3470 b turned out to be mostly clear, with only thin hazes, enabling the scientists to probe deep into the atmosphere. “We expected an atmosphere strongly enriched in heavier elements like oxygen and carbon which are forming abundant water vapor and methane gas, similar to what we see on Neptune”, said Benneke. “Instead, we found an atmosphere that is so poor in heavy elements that its composition resembles the hydrogen/helium rich composition of the Sun.”
To me, our knowledge of exoplanets today is beginning to resemble our knowledge of the planets in the solar system c. 1950. The little data we have gives us a vague idea of what’s there, but there are so many gaps and uncertainties that no one should be confident about drawing any firm conclusions.
