First measurement of the alignment of the rotating orbit on a ‘super-Jupiter’

MADRID, 29 Jun. (EUROPA PRESS) –

An international team of scientists, led by Professor Stefan Kraus of the University of Exeter, has made the first measurement of the alignment of the rotating orbit to a distant ‘super-Jupiter’ planet, demonstrating a technique that could allow advances in the search to understand how exoplanet systems form and evolve.

Specifically, scientists have carried out measurements of the exoplanet ‘Beta Pictoris b’, located 63 light years from Earth.

The planet, located in the constellation Pictor, has a mass about 11 times that of Jupiter and orbits a young star in a Saturn-like orbit in our solar system.

The study, published Monday in ‘Astrophysical Journal Letters’, marks the first time scientists have measured the alignment of the rotating orbit for a planetary system with direct imaging.

Crucially, the results provide a new insight to improve understanding of the history of the formation and evolution of the planetary system.

“The degree to which a star and a planetary orbit are aligned with each other tells us a lot about how a planet was formed. and if several planets in the system dynamically interacted after their formation, “says Professor Kraus.

Some of the earliest theories of the planet formation process were put forward by prominent eighteenth-century astronomers Kant and Laplace. They both observed that the orbits of the planets in the solar system are aligned with each other and with the Sun’s axis of rotation, and concluded that the solar system was formed from a flattened, rotating protoplanetary disk.

“It was a big surprise when it was discovered that more than a third of all nearby exoplanets orbit their host star in orbits that are misaligned with respect to the stellar equator“says Professor Kraus.

“Some exoplanets were even found to orbit in the opposite direction of the star’s direction of rotation. These observations challenge the perception of planet formation as an orderly and orderly process that takes place in a flat, geometrically thin disk,” he adds. .

For the study, the researchers devised an innovative method that measures the small spatial displacement of less than one trillionth of a degree caused by the rotation of ‘Beta Pictoris’.

The team used the GRAVITY instrument on the VLTI, which combines light from telescopes 140 meters apart, to make the measurements. They discovered that the axis of stellar rotation is aligned with the orbital axes of the planet ‘Beta Pictoris b’ and its extended debris disk.

“Gas absorption in the stellar atmosphere causes a small spatial shift in spectral lines that can be used to determine the orientation of the stellar axis of rotation, “explains Dr. Jean-Baptiste LeBouquin, an astronomer at the University of Grenoble in France and a member of the team.

“The challenge is that this spatial shift is extremely small: about 1/100 of the star’s apparent diameter, or the equivalent of the size of a human step on the moon as seen from Earth,” he says.

The results show that the ‘Beta Pictoris’ system is as well aligned as the Solar System. This finding favors planet-planet dispersion as the cause of the orbital obliquities seen in more exotic systems with ‘hot Jupiters’.

However, observations on a large sample of planetary systems will be required to answer this question conclusively. The team proposes a new interferometric instrument that will allow them to obtain these measurements in many more planetary systems that are yet to be discovered.

“A dedicated high-spectral resolution instrument in VLTI could measure rotational orbit alignment for hundreds of planets, including those in long-period orbits,” says Professor Kraus. And he concludes: “This will help us answer the question of how dynamic processes form the architecture of planetary systems.“.

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