Probing an 'Invisible' Exoplanet's Atmosphere 28
astroengine writes "To study the atmospheres of planets beyond the solar system, astronomers have had two choices: pick one that flies across the face of its parent star relative to Earth's perspective (an event known as a transit), or wait for a new generation of more sensitive space telescopes that can directly capture the planet's faint light. Now, there's a third option. Using a cryogenically-cooled infrared detector on a telescope in Chile, astronomers ferreted out beams of light coming directly from Tau Boötis b, a massive planet about 50 light-years from Earth."
Re:"Third option"? (Score:5, Informative)
Why does the "third option" sound so suspiciously similar to the second one? If VLT is not one of the "new generation of more sensitive space telescopes", then I'll eat my shoes.
I believe by "space telescopes," the summary writer was specifically referring to telescopes deployed in space.
Better source (Score:4, Informative)
discovery.com, really? From ESO's press release (http://www.eso.org/public/news/eso1227/):
The team used the CRIRES instrument on the Very Large Telescope (VLT) at ESO’s Paranal Observatory in Chile. They combined high quality infrared observations (at wavelengths around 2.3 microns) [At infrared wavelengths, the parent star emits less light than in the optical regime, so this is a wavelength regime favorable for separating out the dim planet’s signal.] with a clever new trick to tease out the weak signal of the planet from the much stronger one from the parent star.
This method uses the velocity of the planet in orbit around its parent star to distinguish its radiation from that of the star and also from features coming from the Earth’s atmosphere. The same team of astronomers tested this technique before on a transiting planet, measuring its orbital velocity during its crossing of the stellar disc.
Lead author of the study Matteo Brogi (Leiden Observatory, the Netherlands) explains: “Thanks to the high quality observations provided by the VLT and CRIRES we were able to study the spectrum of the system in much more detail than has been possible before. Only about 0.01% of the light we see comes from the planet, and the rest from the star, so this was not easy”.
The majority of planets around other stars were discovered by their gravitational effects on their parent stars, which limits the information that can be gleaned about their mass: they only allow a lower limit to be calculated for a planet’s mass. The new technique pioneered here is much more powerful. Seeing the planet’s light directly has allowed the astronomers to measure the angle of the planet’s orbit and hence work out its mass precisely. By tracing the changes in the planet’s motion as it orbits its star, the team has determined reliably for the first time that Tau Boötis b orbits its host star at an angle of 44 degrees and has a mass six times that of the planet Jupiter in our own Solar System.
[...]
As well as detecting the glow of the atmosphere and measuring Tau Boötis b’s mass, the team has probed its atmosphere and measured the amount of carbon monoxide present, as well as the temperature at different altitudes by means of a comparison between the observations and theoretical models. A surprising result from this work was that the new observations indicated an atmosphere with a temperature that falls higher up. This result is the exact opposite of the temperature inversion — an increase in temperature with height — found for other hot Jupiter exoplanets
Re:Why in Chile? (Score:4, Informative)
In orbit you would get the cryogenic part for free
Not so. You have to cool satellites too as they also receive solar radiation. And getting to orbit certainly isn't free.