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\t\t\t\t\t\t04\/02\/2025<\/span> Using data from the European Space Agency\u2019s Gaia mission, scientists have found a huge exoplanet and a brown dwarf. This is the first time a planet has been uniquely discovered by Gaia\u2019s ability to sense the gravitational tug or \u2018wobble\u2019 the planet induces on a star. Both the planet and brown dwarf are orbiting low-mass stars, a scenario thought to be extremely rare.<\/p>\n<\/p><\/div>\n<\/p><\/div>\n New research, published today, uses data collected by ESA\u2019s Gaia spacecraft to confirm the existence of two mysterious celestial objects. Gaia-4b is a \u2018Super-Jupiter\u2019 exoplanet, and Gaia-5b a brown dwarf. These massive objects are unexpectedly orbiting low-mass stars.<\/p>\n Gaia-4b is a planet orbiting the previously unremarkable star Gaia-4 around 244 light-years away. Gaia-5b orbits the Gaia-5 star, around 134 light-years away from Earth. These two newly discovered objects are nearby, in our own galactic neighbourhood. Their existence challenges current theories of planet formation, and Gaia’s ongoing mission will provide valuable data to help us understand these intriguing objects.<\/p>\n<\/p><\/div>\n \u201cGaia-4b is about twelve times more massive than Jupiter. With an orbital period of 570 days, it is a relatively cold gas giant planet,\u201d explains first author Gu\u00f0mundur Stef\u00e1nsson of the University of Amsterdam, the Netherlands, and first author of the new study.<\/p>\n \u201cWith a mass of around 21 Jupiters, Gaia-5b is a brown dwarf, more massive than a planet but too light to sustain nuclear fusion to be a star,\u201d Gu\u00f0mundur adds.<\/p>\n<\/p><\/div>\n Since its launch in 2013, ESA\u2019s Gaia spacecraft has been building the largest, most precise three-dimensional map of our galaxy. Spinning slowly, it scanned the sky with two optical telescopes, repeatedly pinpointing the positions of two billion objects with unprecedented precision, until its end of science observations on 15 January 2025. Because Gaia precisely tracked the motion of stars \u2013 a technique known as astrometry \u2013 thousands of new objects are expected to be discovered in its data.<\/p>\n<\/p><\/div>\n A planet in orbit around a star creates a tiny gravitational \u2018tug\u2019 that makes the star \u2018wobble\u2019 around its centre of mass and travel in a corkscrew-like motion across the sky. The easiest objects to discover using astrometry are massive and in distant orbits around their parent star. Previously, a few massive brown dwarfs were confirmed to exist by other telescopes who observed their faint glow next to bright stars for which Gaia had detected such a wobble.<\/p>\n That\u2019s in contrast to the transit method, which detects planets as they pass in front of their star and is most likely to find planets in a close orbit. And although detecting a wobble suggests a star might have a planet, there are other potential causes (such as binary star systems), so astrometric discoveries must be confirmed using other methods.<\/p>\n \u201cGaia was repeatedly scanning these stars, building up an increasingly detailed picture over time,\u201d Gu\u00f0mundur says. \u201cIn 2022, Gaia Data Release 3 included a list of stars that appear to be moving as though pulled by an exoplanet. Using ground-based spectroscopic data and the radial velocity technique to investigate these stars, we confirmed our first planet and our first brown dwarf.\u201d<\/p>\n Combining astrometric and radial velocity data allows astronomers to find all the orbital details and the mass of the orbiting object, offering a unique opportunity to create three-dimensional visualisations.<\/p>\n<\/p><\/div>\n \u201cAbout 75% of the stars in the Milky Way are low-mass stars, with masses between about 10% and 60-65% of the mass of the Sun. Because they’re so numerous, they’re also our nearest neighbour stars,\u201d explains Gu\u00f0mundur. \u201cMassive planets around low-mass stars are known to be relatively rare, but when they occur, they cause a larger wobble, and therefore a stronger astrometric signature that is easier to detect.\u201d<\/p>\n<\/p><\/div>\n Whereas a previous exoplanet was found by the Gaia and Hipparcos missions in tandem, the presence of Gaia-4b was revealed by Gaia data alone.<\/p>\n When the next batch of Gaia data is released in 2026, it will contain 5.5 years of mission data that could uncover hundreds \u2013 if not thousands \u2013 of planets and brown dwarfs around nearby stars. That will give us new insights into how these different objects form, and Gaia is paving the way for a new era of astrometric discovery, leading to a deeper understanding of the diverse planetary systems that populate our galaxy.<\/p>\n ESA Research Fellow Matthew Standing is an exoplanet expert. \u201cThis discovery is an exciting tip-of-the-iceberg for the exoplanet discoveries we can expect from Gaia in the future,\u201d he explains. \u201cThe discovery of Gaia-4b is an important breakthrough in the use of Gaia astrometry for exoplanet detection, complimenting the other exoplanet detection methods used by ESA\u2019s Cheops and the upcoming Plato mission.\u201d<\/p>\n “Gaia has seen the telltale signs of known exoplanets before, but this time Gaia revealed an entirely new extrasolar world,\u201d says Johannes Sahlmann, Gaia Project Scientist at ESA. \u201cThe discovery of Gaia-4b shows how Gaia\u2019s detailed measurements complement established exoplanet discovery techniques and offer new opportunities for exoplanet research. The upcoming fourth Gaia data release will be a treasure trove for planet hunters.\u201d<\/p>\n<\/p><\/div>\n “Gaia-4b and 5b: Radial Velocity Confirmation of Gaia Astrometric Orbital Solutions Reveal a Massive Planet and a Brown Dwarf Orbiting Low-mass Stars<\/i>” by Gu\u00f0mundur Stef\u00e1nsson et al is published today in The Astrophysical Journal.<\/i> <\/p>\n \nFor more information, please contact:<\/b>
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\n\t\t\t\t\t\t\t\t\t\t1<\/span> likes<\/small><\/span><\/p>\n<\/header>\nIn brief<\/h2>\n
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Gaia reveals two new mysterious celestial objects<\/h2>\n
\n\t\t\t\t\t\t\t\t<\/figcaption><\/figure>\nFrom wobbles to new worlds<\/h2>\n
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\n\t\t\t\n\t\t<\/div>\n<\/p><\/div>\nTreasure trove for planet hunters<\/h2>\n
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