New research led by the University of Michigan has ruled out Jupiter-sized and larger planets in the nearby binary star system 70 Ophiuchi AB, setting a record-setting level of sensitivity for the historic target while helping prepare future observatories to characterize habitable rocky worlds. Published in The Astrophysical Journal and supported in part by NASA and the Heising-Simons Foundation, the study narrows the search parameters for smaller worlds within the system’s habitable zone.
Record Sensitivity Rules Out Giant Planets in 70 Ophiuchi AB
The study represents the most sensitive modern search for giant planets in the binary system 70 Ophiuchi AB, located about 16 light-years from Earth. As the third-closest binary system to Earth behind Alpha Centauri and 61 Cygni, 70 Oph AB consists of two stars orbiting each other. Using a century’s worth of data combined with new observations from the 6.5-meter Magellan Clay Telescope in Chile and the 2.7-meter Harlan J. Smith Telescope in Texas, the research team ruled out planets with the mass of Jupiter or greater within the inner regions of the system.
Specifically, the data confirmed there are no Jupiter-mass planets within 5 astronomical units of 70 Ophiuchi A and none within half an astronomical unit of 70 Ophiuchi B. “We’re finding out that there isn’t a Jupiter-sized planet, but we’re also opening the latest chapter on this historic system,” said Yiting Li, a postdoctoral researcher in the U-M Department of Astronomy. Michael Meyer, senior co-author and chair of the U-M astronomy department, noted that the team’s precise approach allowed them to determine that a previous radial velocity “wobble” in the stars was caused by surface variations over time rather than a gravitational pull from a massive planet.
Did you know? British astronomer William Jacob claimed the 70 Ophiuchi AB system hosted a planet in 1855, making it the first host of an official exoplanet candidate. While Jacob’s original claim did not survive modern scrutiny, subsequent measurements maintained the possibility of planets in the system for 171 years until this latest analysis.
Implications for NASA’s Habitable World Observatory and SHERA
By establishing precise upper limits on giant planets, the research paves the way for future mission architectures designed to find Earth-like worlds. Roughly half of the stellar systems in the Milky Way feature at least two stars, making binaries crucial targets for understanding planetary formation and habitability. The absence of gas giants in the inner regions leaves open the possibility of finding smaller planets the size of Saturn or rocky worlds within the habitable zone, where temperatures can support liquid water.
“The new limit enables us to design optimum search strategies in the future,” Meyer said. He added that the University of Michigan is part of a team studying a space mission called SHERA, which targets binary systems like 70 Oph AB. The system is also positioned to serve as a target for flagship missions such as NASA’s Habitable World Observatory. Researchers from more than a dozen institutions contributed to the work, including NASA’s Jet Propulsion Laboratory and IPAC at the California Institute of Technology.
Common Questions About the 70 Ophiuchi AB Study
Are there any planets left to discover in the 70 Ophiuchi AB system?
Yes. The study establishes an upper mass limit rather than a complete ban on planets, leaving open the possibility of Saturn-sized or smaller rocky worlds within the habitable zone.
Why was the system’s stellar wobble mistaken for a planet for so long?
Modern measurements of the stars’ radial velocity showed a periodic shift that historical data could not rule out as a Jupiter-sized planet. The new analysis of a century of records and telescope observations proved the wobble stems from natural variations on the stellar surfaces.
How close is the 70 Ophiuchi AB system to Earth?
The binary system is located approximately 16 light-years away, making it the third-closest binary system to Earth after Alpha Centauri at 4.2 light-years and 61 Cygni at 11.4 light-years.
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