Astronomers First Measured The Tilt Of The Orbit Of A Distant Exoplanet
European planetologists found out at what angle an exoplanet rotates around a star in the constellation of the Painter for the first time. Their results confirmed that the classical theory of the formation of planets from a protoplanetary disk is correct, according to an article describing the research published by the scientific journal Astrophysical Journal Letters.
"The direction of rotation of a star can be determined by how strongly certain lines in its spectrum shift, which are associated with the absorption of radiation in the upper layers of the star's atmosphere. The problem is that this shift is extremely small, about 100 times smaller than the apparent size of the sun. It's as if we were trying to see the footprints of astronauts on the moon from Earth," said one of the authors of the study, an astrophysicist from the University of Grenoble (France), Dr. Jean-Baptiste LeBouquin.
LeBouquin and his colleagues observed the second-brightest star in the constellation of the Painter (β Pictoris). This white-yellow dwarf is 64 light-years from the Solar system. β Pictoris and its environment are very young. Their age does not exceed 20 million years.
Astronomers began studying this star system in detail 40 years ago. Then it turned out that it produces an unusual amount of infrared radiation. Later, scientists found out that its source is a gas-dust disk, inside which there is a planet, β Pictoris b. Her first photos were taken by Hubble in 2009.
Since then, due to the size of this gas giant, as well as the small distance between it and the Earth, β Pictoris b has become one of the primary "targets" of planetary research. For example, scientists have long been trying to understand whether the orbit of this planet is tilted to the plane of its star system by 45 degrees, as indicated by the position of the protoplanetary disk, or not.
Deviation of the star axis
European planetary scientists obtained the first such data using the VLTI and GRAVITY instruments, which are installed on the European VLT optical telescope in the Chilean Atacama desert. They can detect even small shifts in the structure of the spectrum of stars, which are associated with the nature of their rotation around their own axis.
Taking advantage of this, scientists observed the brightest point inside the beta Painter. It is related to the radiation that bromine atoms absorb and produce. By the way, this point moves relative to the center of the star, astronomers can understand in which direction and at what speed the sun rotates around its axis.
It turned out that in this respect the artist's beta is not different from the Sun. As in our system, its axis of rotation was almost perpendicular to the orbit of its planet and the protoplanetary disk, deviating from them by only 3-5 degrees.
"In the past, we were very surprised that more than a third of the known exoplanets that rotate near the sun are located in orbits that presumably do not coincide with the position of the equator of their stars. Some planets even moved in retrograde orbits. All this called into question the theory that planets arise inside thin gas-dust disks," explained another author of the work, Professor at the University of Exeter (UK) Stefan Kraus.
The first practical observations of this kind, as Kraus notes, suggest that the classical theories of planet formation are still closer to the truth than alternative explanations. Astronomers hope that subsequent measurements of the direction and speed of rotation of other stars will help them prove this, or provide evidence that planets can occur in different scenarios.