Astronomers spot hidden ‘companions’ around eight bright stars

20 Jun 2024

Artist impression of a brown dwarf orbiting close to a bright star. Image: ESA

By combining the power of the Gaia space telescope and an instrument on the Very Large Telescope, researchers were able to spot previously hidden stars and brown dwarfs that were shrouded in the light of their nearby suns.

Scientists have managed to take images of faint objects next to bright stars, by combining the power of a space and ground-based telescope.

The brightness of a shining star means it can be difficult to get images of any objects that are close to it, such as planets. The European Space Agency (ESA) compared it to taking a picture of a firefly next to a bright streetlight.

To resolve this, researchers at the ESA and the European Southern Observatory (ESO) looked at the catalogue from Gaia, the ESA space telescope mission. This catalogue lists hundreds of thousands of stars that are suspected to have a companion – which could be other stars or even planets.

Although these companion objects are not bright enough to be seen by Gaia directly, the researchers said Gaia was able to detect “tiny wobbles” in the paths of the more luminous host star.

From this catalogue, the team detected eight stars that they targeted with Gravity – the advanced near-infrared interferometer at the ESO’s Very Large Telescope. This instrument works by infrared light from different telescopes to pick up tiny details in faint objects – a technique called interferometry.

Thanks to this technique, the team caught the light signal of all eight predicted companions and said seven of them were previously unknown. Three of these companions were faint stars, while the other five consisted of brown dwarfs – celestial objects that are bigger than the heaviest of planets but lighter than the lightest of stars.

“We have demonstrated that it is possible to capture an image of a faint companion, even when it orbits very close to its bright host,” said ESO scientist Thomas Winterhalder. “This achievement highlights the remarkable synergy between Gaia and Gravity.

“Only Gaia can identify such tight systems hosting a star and a ‘hidden’ companion, and then Gravity can take over to image the smaller and fainter object with unprecedented accuracy.”

Having tested the power of these two systems working together, the researchers plan to track down potential planet companions of other stars listed in the Gaia catalogue. Gaia was launched in 2013 to chart a 3D map of stars in the Milky Way and reveal the composition, formation and evolution of our galaxy.

Earlier this year, researchers looking through Gaia data stumbled upon the most massive stellar black hole discovered yet in our Milky Way galaxy – and it is 33 times the mass of our sun.

Updated, 11.30am, 20 June 2024: This article was amended to clarify that the eight companions were not planets, but were actually faint stars and brown dwarfs.

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Leigh Mc Gowran is a journalist with Silicon Republic