Directly observed planet undergoing nuclear fusion is found thanks to Gaia

 By University of Exeter 

January 11, 2023

Combining the best-fitting DRIFTPHOENIX models with the combined R 500 GRAVITY K-band spectra of HD 206893c and B (red and light purple, respectively) (black and light brown). The fit also incorporated historical spectrophotometry of B, which is shown in bright orange, green, and blue. A number of samples taken from the posterior distribution are displayed for the model spectra as thin lines.

                               A new exoplanet that is showing symptoms of nuclear fusion in its core has been found by scientists thanks to the minor variations of a distant star.

A new exoplanet orbiting the star HD206893 has been discovered by an international team of researchers led by Professor Sasha Hinkley at the University of Exeter. The planet was discovered about 750 trillion miles from Earth and is about 30% bigger than our sun.

The Very Large Telescope's GRAVITY instrument, which synchronises the VLT's four primary telescopes to function as a single, much bigger telescope using optical interferometry, was used by the astronomers to confirm the existence of the far-off planet.

This method enables GRAVITY to describe the planet's atmosphere and measure the spectrum of light emitted from the planet, as well as the position of the planet in its orbit, with exceptional precision.

Using this method, the study team came to the conclusion that the newly discovered planet exhibits evident "brightening" as a result of nuclear fusion caused by the burning of deuterium, or "heavy hydrogen," in its core.

This is one of the earliest detections of a planet whose existence was largely inferred from the astrometric motion of the host star as it passes across the sky, and it represents a significant advance in the search for new, far-off planets.

The team predicts that many of these exoplanets will be able to be defined by direct imaging, as with this recent finding, with the ESA Gaia mission projected to show the way to countless such exoplanets.

We may have made the first direct identification of a "Gaia exoplanet," according to Professor Hinkley, therefore the finding of HD206893c is significant for the study of exoplanets.

In 2017, researchers first found the brown dwarf HD206893B circling the host star. However, detailed measurements of the host star's proper motion by the Gaia mission and long-term surveillance by the ESO HARPS instrument also suggested the possibility of an inner, lower mass partner.

The HD206893c planet, which circles its host star at a distance of around 300 million miles, nearly halfway between the orbits of Mars and Jupiter in our own solar system, and has a mass higher than Jupiter was revealed to be this partner by astronomers using the GRAVITY instrument.

The finding provides verifiable proof that exoplanets may be directly detected by contemporary sensors on orbital scales that are comparable to those of our own solar system.

Additionally, because the planet is on either side of the deuterium-burning limit, which is generally thought to be roughly 13 Jupiter masses, it may help scientists better understand how to distinguish between objects that are brown dwarfs and genuine extrasolar planets.

Professor Hinkley said, "This discovery is also highly significant because it demonstrates that we can now directly characterise the atmospheres of these exoplanets at around two to four times our Earth/Sun distance, where we know from prior research that they most typically live."

In October 2022, the journal Astronomy & Astrophysics approved the study, with the working title "Direct Discovery of the Inner Exoplanet in the HD206893 System," for publication.