Astronomers discover a colossal exoplanet orbiting a "wobbling" star

They pinpointed the massive planet, with 16 times the mass of Jupiter, in data from ESA's Gaia telescope dataset.
Chris Young
An artist's impression of the Gaia telescope.
An artist's impression of the Gaia telescope.

ESA / ATG medialab 

A team of astronomers discovered a new planet using a new method that leveraged the wealth of data collected by the European Space Agency's (ESA's) Gaia space observatory.

The new exoplanet, dubbed HIP 99770 b, is roughly 16 times the mass of Jupiter. It was pinpointed using a new technique that could be used in the future to help find more direct images of alien worlds.

How astronomers image distant planets

Astronomers have long used several methods to detect exoplanets — any planet not part of our solar system. These methods fall into two broad categories: direct and indirect imaging.

Historically, most exoplanets have been discovered via indirect methods, such as the transit method, which measures the periodic drop in light of a distant star as an exoplanet passes between the star and an observatory's field of view.

Direct images provide insight into a planet's composition and temperature, whereas indirect photos provide insight into a planet's mass and orbital trajectory.

To date, astronomers have detected more than 5,000 exoplanets, but only about 20 of those were imaged directly. This is due to the limitations of our current imaging technology, which means that a planet has to be widely separated from its parent and much more massive than Jupiter to be observable.

Such planets are exceedingly rare, and previous observations have primarily hoped to detect them by chance by observing relatively old star systems.

Altering our perspective of the cosmos

The team behind the new exoplanet discovery has used a new method to track down a coveted direct image. "We wanted a different strategy," Thayne Currie, National Astronomical Observatory of Japan (NAOJ), Hilo, Hawaii, and the University of Texas-San Antonio, explained in a press statement.

Currie and colleagues turned to the Hipparcos-Gaia Catalogue of Accelerations, which combines data from the Gaia space observatory with ESA's previous star mapping mission, Hipparcos. This allowed them a 25-year baseline for comparing the precise positions of stars.

Using this data, they could pinpoint stars that had changed their position in the night sky in a way that suggested they hosted a massive gas giant larger than Jupiter.

They then took follow-up observations of those stars in 2020 and 2021, using NAOJ’s Subaru Telescope on Mauna Kea, Hawaii. Using this method, they discovered HIP 99770 b, which has roughly 16 times the mass of Jupiter, orbits a host star nearly twice the size of the Sun, and has an orbit three times larger than Jupiter's.

The discovery could have a wide-ranging impact on our understanding of the cosmos. "It provides a new path forward to discovering more exoplanets and characterizing them in a far more holistic way than we could do before," Thayne said.

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