A Planet with Two Suns—How Did This Super-Jupiter Stay Hidden for Years?
A Hidden World in Archived Data
The Gemini Planet Imager, or GPI, was recently retired from the Gemini South telescope in Chile. It is now being relocated to Mauna Kea, Hawai‘i, for upgrades and new observations in the northern hemisphere. Because of this transition, scientists decided to revisit GPI’s extensive archive. That archive includes observations of more than five hundred stars.
Although GPI was designed for direct exoplanet imaging, it has detected only six planets so far. This low number highlights how difficult it is to suppress bright starlight. As a result, faint planetary companions often remain invisible. However, this limitation also raises a key question. Could more hidden worlds still be buried in old data?
A Super-Jupiter Orbiting Two Suns
HD 143811 AB b is a massive super-Jupiter that orbits two stars instead of one. The planet lies at a distance of roughly sixty astronomical units. In our solar system, that would place it far beyond Pluto.
For a circumbinary planet, however, this orbit is surprisingly close. Most previously imaged binary-star planets orbit hundreds of astronomical units away. For example, one known planet circles its stars at nearly five hundred AU. That distance is closer to the Sun’s theoretical gravitational lens than any planet around our Sun.
So how did HD 143811 AB b survive so close to two stars without being torn apart by gravity?
Unusual Circumbinary Planet Orbits
Binary star systems create unstable gravitational environments. Therefore, planets are usually expected to form or survive only at large distances. In this case, HD 143811 AB b defies that expectation.
Its orbit suggests that our understanding of circumbinary dynamics is incomplete. Moreover, it hints that closer-in planets around binary stars may be more common than previously thought.
Competing Theories of Planet Formation
This discovery challenges existing models of planet formation in binary systems. Most wide-orbit circumbinary planets are believed to form through gravitational instability. In that process, a massive protoplanetary disk collapses rapidly under its own gravity.
However, HD 143811 AB b complicates this idea. One possibility is core accretion. In that scenario, the planet formed closer to the stars and later migrated outward. Alternatively, it may still be a product of disk instability.
So which mechanism dominates in binary systems? And how many similar planets have astronomers already overlooked?
A Young and Extremely Hot Super-Jupiter
HD 143811 AB b is very young by cosmic standards. It formed roughly thirteen million years ago. At that time, dinosaurs had already vanished from Earth.
Its host stars belong to the Scorpius–Centaurus association. This region is one of the closest large star-forming groups to our solar system. Because these stars are young and energetic, they emit intense radiation. Consequently, the planet reaches temperatures near seven hundred sixty-nine degrees Celsius.
The planet completes one orbit every three hundred years. Meanwhile, its two stars circle each other every eighteen days. Under such extreme and unstable conditions, life seems unlikely. Still, the system offers valuable clues about planetary survival.
Why Old Data Still Matters
HD 143811 AB b does not resemble science fiction worlds with twin sunsets. Even so, its discovery shows the power of reexamining archival data. Sometimes, new insights emerge simply by asking better questions.
The Future of Direct Exoplanet Imaging
As the Gemini Planet Imager undergoes upgrades, its capabilities will improve. In particular, a more advanced coronagraph will help block starlight more effectively. As a result, astronomers expect to detect planets closer to their host stars.
Ideally, future discoveries will come from real-time observations. Still, this finding sends a clear message. Many extraordinary exoplanets may still be hiding in plain sight, waiting for someone to look again.
Source: A Planet with Two Suns—How Did This Super-Jupiter Stay Hidden for Years?
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