Tech UPTechnologyFirst observation of iron in the atmosphere of an...

First observation of iron in the atmosphere of an exoplanet

Exoplanet exploration, in full swing since the 1990s, has provided astonishing data on what is happening on other extraterrestrial worlds. In addition, it provides clues as to whether other planets could be suitable for supporting life.

One of these fascinating discoveries, recently accepted for publication in The Astrophysical Journal Letters , consists of the first direct detection of iron in the atmosphere of an exoplanet, called KELT-9b. The finding consists of emission lines of uncharged iron atoms in the planet’s light spectrum. The detection of exoplanets is based on the ‘shadow’ they cast on their antitrione star. Specifically, the star KELT-9, around which this ‘exworld’ orbits every 36 hours, projects a brilliant light that outshines the planet, making the observation ‘especially difficult’ , according to a publication on the website of scientific news

What do we know about this alien world?

The star and planet are located at a distance of approximately 620 light years from Earth in the constellation Cygnus. The star has a temperature of more than 10,000 degrees, almost double that of our Sun. The planet KELT-9b, for its part, is a gas giant bigger than Jupiter; and it is comparatively much closer to its star, about thirty times closer to Earth than the Sun. Due to its proximity to its host star, a year on the planet lasts about one and a half Earth days.

The researchers already sensed that there should be iron in the atmosphere of this exoplanet. A few years ago, they already saw signs of iron by studying the light of the stars as the planet passed in front of them (the usual method of detecting exworlds like this). In recent observations, the researchers detected the planet’s light directly for the first time , a complicated fact, as we said, because it is dwarfed by the light from its star.

During the middle of the planetary year of KELT-9b, the nightside of the planet is oriented towards Earth, but it is too dark to be seen. Therefore, the researchers only had eight hours, just before the planet disappeared behind its star, to observe the illuminated, brighter and more detectable side.

Lorenzo Pino, lead author of the study, compares the search for the exoplanet’s light under the glare of its host star to observing a firefly near a street lamp: “A few years ago we saw the shadow of the ‘firefly’ or, in our case, the shadow of the exoplanet. Now we have seen the firefly directly. “

And how have they detected iron?

The researchers made their observations on the Spanish island of La Palma de Gran Canaria on the night of July 22, 2018 using an Italian telescope, the Telescopio Nazionale Galileo. This telescope uses the HARPS-N tool, a spectrograph that can split light and reveal the presence of specific atoms and molecules. The researchers extracted the trace of the iron atoms using a technique called cross-correlation.

Pino compares the cross-correlation with photo retouching: “The star is stationary, but the planet is moving. Cross correlation is a type of filter that moves with the planet. This allows us to isolate the planetary light. “

The researchers believe that the iron in the atmosphere of exoplanet KELT-9b warms the upper part of the atmosphere , hotter than the lower part: the iron would be absorbing the energy of its star, heating the atmosphere. On Earth, a similar process takes place; in this case, it is ozone that heats the upper layers.


‘Neutral Iron Emission Lines From The Day-side Of KELT-9b. The GAPS Program With HARPS-N At TNG XX ‘. By: Lorenzo Pino et al. Accepted for publication in The Astrophysical Journal Letters.

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