Gaia's Contribution to the Search for Exoplanets

One mission that complements NEID is the European Space Agency’s (ESA) Gaia spacecraft. By precisely monitoring the positions and motions of stars in our galaxy, Gaia is transforming our understanding of numerous astrophysical phenomena. With its exceptional accuracy, Gaia is expected to detect thousands of exoplanets orbiting nearby stars.

Figure 1. Scientists Unveil the Discovery of a Massive Hidden Planet.

In contrast to the radial velocity method used by NEID, Gaia employs astrometry to track a star's motion. This technique measures the subtle shift in a star's position caused by the gravitational pull of an orbiting planet, by observing how the star moves in relation to distant or nearby stars. Figure 1 shows Scientists Unveil the Discovery of a Massive Hidden Planet.

Sifting Through Gaia's Planet Candidates

In the latest Gaia data release, a list of stars was published that seem to be moving as though influenced by an exoplanet — known as the Gaia Astrometric Objects of Interest (Gaia-ASOIs). However, the motion of these stars may not always be caused by a planet. "The apparent motion might instead be due to a pair of stars so close together that Gaia cannot distinguish them as separate objects," explained Guðmundur Stefánsson, assistant professor at the University of Amsterdam and lead author of a paper in The Astrophysical Journal. "The tiny positional shifts that seem planet-induced could actually result from the near-perfect cancellation of the larger shifts from both stars."

To separate these binary stars from genuine planets, follow-up observations with spectroscopy are necessary. The team used NEID along with two other spectrographs: the Habitable-zone Planet Finder (HPF) on the 10-meter Hobby-Eberly Telescope at McDonald Observatory in Texas and the FIES Spectrograph on the 2.6-meter Nordic Optical Telescope at La Palma in the Canary Islands.

With these advanced instruments, the team followed up on 28-star systems with planet candidates identified by Gaia. Of the 28, 21 were confirmed as false positives, revealing them to be binary star systems rather than planets. Additionally, they confirmed one system contained a brown dwarf — an object with a mass between that of a planet and a star — and one system hosted a giant planet.

Gaia-4b: A Massive World Orbiting a Small Star

The newly discovered exoplanet, Gaia-4b, boasts an orbital period of 570 days and a mass 12 times that of Jupiter, orbiting a star with only 64% of the Sun’s mass. Not only is Gaia-4b the first planet detected by Gaia using the astrometric technique with a fully independent and confirmed orbital solution, but it is also one of the most massive planets known to orbit a low-mass star.

“It is an exciting time for both NEID and Gaia,” says Jayadev Rajagopal, scientist at NSF NOIRLab and co-author of the paper. “Gaia is living up to its promise of detecting planetary companions to stars with highly precise astrometry, and NEID is showing that its long-term radial velocity precision can detect low-mass planets around these stars. As more candidate planets are analyzed with the remaining year of data, this work signals a future where Gaia's discoveries of planets and brown dwarfs will be confirmed — or refuted — by NEID data.”

In addition to detecting Gaia-4b and Gaia-5b, the authors offer a first look at the 'false positive rate' of the Gaia Astrometric Exoplanet catalog, which ranges from 30% to 80% in their sample. This underscores the crucial role of ground-based observations, such as those made with NEID, in confirming planetary candidates during the Gaia-driven era of planet detection.

Source: SciTECHDaily

Cite this article:

Priyadharshini S (2025), "Scientists Have Discovered a Massive Hidden Planet", Anathemas, pp. 231