A spacecraft exploring the Milky Way has identified a huge exoplanet, Gaia-4b, which possesses a mass 12 times that of Jupiter, alongside a brown dwarf, Gaia-5b. Both of these astronomical entities revolve around stars smaller than the Sun, albeit at considerable distances. Gaia-4b is situated 244 light-years away, while Gaia-5b is located 134 light-years from Earth.

These findings were achieved by the European Space Agency’s (ESA) Gaia spacecraft, which has recently wrapped up its mission due to diminishing fuel supplies. The discoveries were validated with supplementary instruments, affirming their accuracy. Though Gaia officially ceased its scientific observations on January 15, the mission is anticipated to disseminate a substantial amount of data next year, possibly leading to additional significant discoveries.

“This finding marks an exhilarating beginning for the exoplanet discoveries we can look forward to from Gaia in the future,” remarked Matthew Standing, an ESA research fellow.

According to NASA, the total number of confirmed exoplanets has now exceeded 5,800, with thousands more pending verification. Given the enormity of the universe, filled with hundreds of billions of galaxies and trillions of stars, the chances of uncovering more planets are vast.

Gaia-4b is categorized as a super-Jupiter, a gas giant with a relatively cool temperature, completing its orbit around its star in roughly 570 Earth days. The star it orbits has about 64% of the Sun’s mass, which makes Gaia-4b one of the most significant known planets orbiting a small star.

Gaia-5b, the brown dwarf, is occasionally described as a “failed star” because it does not possess the mass required for nuclear fusion. It orbits an even smaller star, which has around 34% of the Sun’s mass, in a slightly shorter timeframe than an Earth year. Despite not being a fully-fledged star, Gaia-5b remains substantial—about 21 times the mass of Jupiter. For reference, Jupiter itself has a mass equivalent to roughly 318 Earths.

The findings were published in *The Astrophysical Journal*.

Gaia-4b signifies the first independent triumph of the Gaia spacecraft utilizing the “wobble” technique, also known as astrometry. Since its launch in 2013, Gaia has employed a duo of optical telescopes to meticulously track stellar movements. Researchers believe this method could unveil thousands of new exoplanets.

The gravitational influence of orbiting planets can induce their host stars to wobble in a corkscrew-like pattern, which astronomers examine to discover new planets. However, validation from other telescopes is critical, as alternative factors—such as the proximity of a neighboring star—could similarly induce such movements. The WIYN 3.5-meter Telescope at the Kitt Peak National Observatory in Tucson, Arizona, was instrumental in confirming these findings.

“Massive planets surrounding low-mass stars are understood to be relatively uncommon,” stated Guðmundur Stefánsson, lead author of the study. “Yet when they do exist, they create a more pronounced wobble, and consequently, a stronger astrometric signature that is simpler to detect.”

These findings underscore the potential of Gaia’s data, providing a glimpse into the multitude of exoplanets that may still be awaiting discovery.