For the first time, variants of a single chemical element have been found in the atmosphere of a planet outside our solar system. Dutch researchers published Their findings This Wednesday in nature.
Astronomers specifically searched for carbon isotopes. Isotopes are variants of the same element: they have the same number of protons in the nucleus, but a different number of neutrons. They are chemically almost the same, but their masses are different. Under different conditions in the atmosphere, one variant occurs more than the other. The interrelationships say something about the origin of the planet.
The discovery of isotopes has not yet been successful. Astronomers were already able to distinguish different types of particles in the atmospheres of exoplanets. Each molecule absorbs radiation in slightly different colors. Isotopes work, too, but the difference in color is much smaller and some isotopes are rare. Therefore, it is difficult to detect it from a distance.
Dutch astronomers have now succeeded in distinguishing between carbon thirteen (six protons and seven neutrons) and carbon twelve (six protons and six neutrons) in the atmosphere of an exoplanet. “We got a stronger signal by pointing the telescope at the planet longer and knew exactly what color to look for the difference,” says Ignas Snellen of Leiden University, one of the participating astronomers.
They found isotopes in the atmosphere of TYC 8998-760-1 b. This gas giant is fourteen times the mass of Jupiter and orbits a star 300 light-years from Earth. It comes from a “young” planetary system. Its parent star is about seventeen million years old. “The little planets are bright,” says Snellen. And his long distance from his star mother [honderzestig keer zo ver als de zon van de aarde] Its radiation makes it well distinguished from that of a bright star. This is why this planet is a relatively easy target.”
“A very impressive result,” says Alex de Kotter, an astronomer at the University of Amsterdam who was not involved in the study. “It is a tough task to convince your colleagues that you have observed isotopes. But as far as I am concerned, it has worked. They confirm their findings with a very rigorous statistical analysis.”
Remarkably, the team found relatively more carbon-thirteenths than they would expect from a small planet. Only at a great distance from the star can ice form in the gas disks that make up the planets. This ice is rich in carbon thirteen. “This provides a basis for the fact that the exoplanet formed at least beyond that ice boundary and wasn’t pushed away until much later,” says de Kotter. “Whether it is possible for such a massive planet to form at a distance of one hundred and sixty times the distance between the Earth and the Sun, where it is now, I wonder. Far from being a star, there is usually not much gas and dust left, which are the building materials for planets.”
A version of this article also appeared in
NRC on the morning of July 15, 2021
“Subtly charming tv fanatic. Introvert. Thinker. Alcohol maven. Friendly explorer. Certified coffee lover. Infuriatingly humble food junkie. Typical reader.”