Photo: US Naval Observatory
Astronomers have found evidence that an Earth-sized planet could maintain a stable orbit in a double-star system just 16 light-years from Earth, supporting the possibility that potentially habitable worlds can exist around two stars, ScienceAlert reports.
The research focused on the 70 Ophiuchi AB system, which consists of two orange dwarf stars. Researchers estimate that the stars have around 88% and 73% of the Sun’s mass and are approximately three billion years old.
The system has attracted scientific interest for centuries. Astronomer William Herschel identified it as a binary star system more than 250 years ago.
The international research team analyzed recent and historical radial velocity measurements, including observations of the primary star collected over a century using eight different instruments. This technique detects tiny changes in a star’s motion caused by the gravitational influence of other objects.
“Our Solar System, with only one star, is actually somewhat unusual. Many stars have companions,” said study co-author Stephen Kane, an astrophysicist at the University of California, Riverside.
A companion star might be expected to disrupt the orbit of an Earth-like planet in the habitable zone. However, simulations showed that stable orbits could still exist within the primary star’s habitable zone.
“We found that stable orbits are possible in the habitable zone of the primary star. You might expect the second star to disrupt their stability, but that is not always the case in practice,” said co-author Skylar D’Angiolillo, a researcher in Earth and planetary sciences at UC Riverside.
The researchers also ruled out Jupiter-mass planets orbiting the primary star at a distance of around five astronomical units, roughly equivalent to Jupiter’s distance from the Sun.
The findings are particularly relevant because, in 1855, British astronomer William Jacob reported a suspected planet in the 70 Ophiuchi system, making it one of the earliest systems in which an exoplanet was proposed.
The study does not confirm the presence of an Earth-sized planet in the system. Instead, it demonstrates that a planet of that size could potentially maintain a stable orbit in a region where liquid water might exist under suitable conditions.
