The migrant planet that has approached its star

Rebuilt the story of the migrating planet that moved from its orbit to get closer to its star.

To tell it, the chemical signatures left in its atmosphere by six molecules.

The characteristics of this alien world, a hot gas giant called HD 209458b, are published in the journal Nature by the group of the National Institute of Astrophysics (Inaf) coordinated by Paolo Giacobbe.

The study is based on the observations of the Galileo National Telescope (Tng), located on the top of the island of San Miguel de La Palma (Canary Islands). The migrating planet was first observed 20 years ago and orbits its star in about three and a half days, at a distance of just over 7 million kilometers, about one twentieth of that separating the Earth from the Sun Therefore, it has a high temperature, equal to about 1200 degrees centigrade.

The six molecules, found for the first time simultaneously on an alien planet, are water, carbon monoxide, hydrogen cyanide, methane, ammonia and acetylene. The INAF researchers have identified them by studying four different transits of the planet in front of its star with the Giano-B instrument of the Tng. In fact, during the transits, experts explain, the star's light is filtered by the planet's atmosphere, highlighting the footprints of the molecules. According to the INAF researchers, “the presence of these molecules indicates that the planet's atmosphere is richer in carbon than in oxygen. Sign - they conclude - that it formed at great distances from its parent star, higher than that between Mars and the Sun, and then migrated in the direction of the star until the distance in which we observe it today,about a tenth of that which separates Mercury from the Sun ”.