ESO reveal new way to probe the atmospheres of exoplanets

For the first time scientists will examine the atmospheres of non-transiting exoplanets

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ESO/L. Calçada

An artist's impression of Tau Boötis b


It must be exciting to discover an exoplanet. But the faint drop in light detected by telescopes like Kepler as these planets transit their parent stars doesn’t really give too much away, and up until now, if a planet didn’t transit its star, the possibility of discovering much about it was very unlikely indeed.

When a planet passes in front of its star it imprints the properties of the atmosphere onto the starlight. As no starlight shines through a non-transiting planet's atmosphere towards Earth, it has so far been impossible to study these atmospheres.

But thanks to a clever new technique developed by astronomers at ESO’s Very Large Telescope (VLT), the ability to determine the atmosphere, mass and orbit of a non-transiting planet has finally been realised.

Scientists have used the VLT to directly catch the faint glow around Tau Boötis b, one of the first exoplanets to be discovered, revealing the planets atmosphere, exact mass and orbit.

Using high quality infrared observations from the VLT’s Cryogenic InfraRed Echelle Spectrometer (CRIRES), the international team was able to tease out the weak signal of the planet from the much stronger one of the parent star. At infrared wavelengths, the star emits much less light, making it easier to separate out the exoplanet’s dim signal.

As most exoplanets don’t transit their parent stars, and are instead detected by their gravitational effects on their parent stars, this new technique is likely to reveal a great deal about many planets that up until now have remained a mystery. 

 

 

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