We have discovered six new exoplanets by looking at hot gas nearby. Carole Haswell at the Open University in the UK and her colleagues made the discovery by studying nearby stars that the exoplanets orbit.
The six exoplanets are all extremely hot, with temperatures of between 1100掳C and 1800掳C. They range in mass from around 2.6 times the mass of Earth up to almost half Jupiter鈥檚 mass.
Some exoplanets are located much closer to their stars than planets in our solar system are to the sun. When an exoplanet orbits close to stars, its atmosphere can erode, causing a cloud of gas to dissipate.
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The researchers looked at existing data from around 3000 sun-like stars, and narrowed these down to 40 that appeared to be missing a chromosphere, a gaseous layer that comprises part of the outer atmosphere of stars.
The team then carried out measurements of the 40 candidate stars from the European Southern Observatory in Chile and the Haute-Provence Observatory in France. They found six exoplanets orbiting three stars: DMPP-1, DMPP-2 and DMPP-3.
It turns out that these stars do have chromospheres, but they are hidden by a cloud of gas released by the nearby exoplanets.
鈥淲hen we鈥檙e looking at the star, we鈥檙e looking through this shroud of thin gas that鈥檚 been lost from a very hot planet,鈥� says Haswell. The gas absorbs light in specific wavelengths corresponding to its chemical make-up.
鈥淚t鈥檚 exactly those same wavelengths of light that the chromosphere of a star emits in, so it鈥檚 like the perfect shroud to hide the chromosphere while leaving the rest of the star visible,鈥� says Haswell.
The technique only works for finding extremely hot planets that are losing mass as they orbit close to stars, says Haswell, so it won鈥檛 directly help in the search for an Earth-like planet.
But, she says, the technique may help astronomers efficiently find other low-mass rocky planets orbiting nearby stars.
Journal reference: Nature Astronomy,
