(ORDO NEWS) — Brown dwarfs, mysterious objects found at the interface between stars and planets, are important to our understanding of both stellar and planetary populations.
However, in nearly three decades of searching, only 40 brown dwarfs around stars have been imaged. An international team led by researchers from the Open University and the University of Bern directly imaged the four new brown dwarfs using an innovative new search method.
Brown dwarfs are mysterious astronomical objects that fill the gap between the heaviest planets and the lightest stars, with a combination of stellar and planetary characteristics. Thanks to this hybrid nature, these mysterious objects are critical to improving our understanding of both stars and giant planets.
Brown dwarfs that orbit a parent star at a sufficiently large distance are of particular value because they can be photographed directly – unlike those that are too close to their star and therefore hidden by its brightness.
This gives scientists a unique opportunity to study the details of the cold, planet-like atmospheres of brown dwarf companions.
However, despite significant efforts to develop new observational technologies and imaging techniques, direct detections of brown dwarf companions around stars remain quite rare, with only about 40 systems discovered in nearly three decades of searches.
Researchers led by Mariangela Bonavita of the Open University and Clémence Fontanive of the Center for Space and Habitat (CSH) and NCCR PlanetS at the University of Bern have directly discovered four new brown dwarfs, as they report in a study just published in Monthly Notices of the Royal Astronomical.
Society MNRAS. This is the first time that several new systems with brown dwarf companions have been simultaneously detected at wide orbital distances.
Innovative search method
“Companions of brown dwarfs in wide orbits are rare, and their direct detection is fraught with enormous technical difficulties, because the host stars completely blind our telescopes,” says Mariangela Bonavita. Most of the research done so far has focused on random stars from young clusters.
“An alternative approach to increase the number of detections is to observe only those stars that show signs of the presence of an additional object in their system,” explains Clemence Fontanive.For example, the way a star moves under the gravitational pull of a companion can be an indicator of the existence that companion, be it a star, a planet, or something in between.
“We have developed the COPAINS tool, which predicts the types of companions that may be responsible for the observed anomalies in stellar motions,” continues Clemence Fontanive.
Using the COPAINS tool, the research team carefully selected 25 nearby stars that appeared promising for direct detection of hidden low-mass satellites based on data from the European Space Agency’s (ESA) Gaia spacecraft.
Using the SPHERE planetary finder on the Very Large Telescope in Chile to observe these stars, they have successfully discovered ten new satellites orbiting Jupiter to Pluto, including five low-mass stars, a white dwarf (dense stellar remnant) and four new brown dwarfs.
Significant increase in detections
“These results greatly increase the number of known brown dwarfs orbiting stars at large distances and significantly increase their detection rate compared to any previous imaging survey,” explains Mariangela Bonavita.
While this approach is currently limited to the signatures of brown dwarfs and stellar companions, future phases of the Gaia mission will allow these techniques to be applied to lower masses and discover new giant exoplanets.
Clemence Fontanive adds: “In addition to making so many new discoveries at once, our program also demonstrates the power of these search strategies.”
“This result was only possible because we believed that when space and ground-based tools are combined to directly capture exoplanets, the whole is greater than the sum of its parts. We hope this will usher in a new era of synergy between different detection tools and techniques,” concludes Mariangela Bonavita.
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