Seventy Ophiuchi Binary Star System Yields No Jupiter-Sized Worlds After More Than 170 Years
Astronomers studying the binary star system 70 Ophiuchi AB, located 16 light-years from Earth, have ruled out the presence of Jupiter-sized planets within its inner regions after examining data collected since 1855.
The investigation examined the third closest binary star system to Earth, following Alpha Centauri at 4.2 light-years and 61 Cygni at 11.4 light-years. Merging about 100 years of past measurements with fresh data gathered by the 6.5-meter Magellan Clay Telescope at Chile’s Las Campanas Observatory and the 2.7-meter Harlan J. Smith Telescope at McDonald Observatory in Texas, the team achieved the most sensitive modern search for giant planets in the system.
Historical Planet Search Origins in 1855
The pursuit of planets within 70 Ophiuchi AB began 171 years ago. In 1855, British astronomer William Jacob proposed that the binary system contained a planet, marking the first time an exoplanet candidate was officially suggested for any star system.
Although Jacob’s original claim failed to withstand subsequent scientific scrutiny, observations gathered over the following decades continued to support the possibility of hidden worlds. Changes in the stars’ radial velocity created a detectable wobble in measurements of their light, a phenomenon typically caused by the gravitational pull of an orbiting planet.
By separating true planetary indicators from intrinsic stellar variations, the recent study ruled out that previous hypothesis. Yiting assembled an absolutely huge amount of data from all over the world and carefully explored all possibilities,
said Michael Meyer, a senior co-author of the study and chair of the University of Michigan’s astronomy department. It’s a cautionary tale about how stellar activity can mimic planet signals using the radial velocity.
Exclusion Zones Around Seventy Ophiuchi A and B
The research team established precise boundaries regarding where massive planets cannot exist within the binary system. Around the primary star, 70 Ophiuchi A, scientists ruled out planets with masses equal to or greater than Jupiter’s within a distance of 5 astronomical units. An astronomical unit represents the average distance between Earth and the Sun, which is approximately 93 million miles.
Around the secondary star, 70 Ophiuchi B, researchers excluded Jupiter-sized planets within a much tighter radius of half an astronomical unit. These limits successfully resolved persistent questions regarding the system’s inner architecture while significantly improving the precision of the stars’ known orbits.
It’s a mix of disappointment and excitement,
said Yiting Li, a postdoctoral researcher in the University of Michigan’s Department of Astronomy. We’re finding out that there isn’t a Jupiter-sized planet, but we’re also opening the latest chapter on this historic system.
Future Observations Targeting Smaller Worlds
While the study eliminates giant planets from the surveyed regions, it leaves open the possibility that smaller worlds, including Saturn-sized planets and rocky bodies, remain undiscovered. Finding such worlds within the system’s habitable zone remains a primary objective for upcoming astronomical instrumentation.
The new limit enables us to design optimum search strategies in the future,
Meyer said. In fact, the University of Michigan is part of a team studying a space mission called SHERA that will focus on binaries, where this system is one of a handful of targets. 70 Ophiuchi AB will certainly be a target of flagship missions, such as NASA’s Habitable World Observatory.
Researchers representing over twelve organizations contributed to the study, which featured participation from NASA’s Jet Propulsion Laboratory and the California Institute of Technology’s IPAC, alongside financial support from the Heising-Simons Foundation.