For over a decade, a tiny planet was hiding in plain sight — 100 times too faint to notice easily, even with powerful telescopes. Now astronomers have finally spotted it, and it turns out to be a record-breaker.
Beta Pictoris d, a newly discovered world orbiting a star 63 light-years away, is the faintest planet ever caught in a direct photograph taken from Earth's ground-based telescopes. The discovery, published today in The Astrophysical Journal Letters, came as a surprise to the team. "We initially wanted to look more at a known planet in the system, Beta Pictoris b, to see how it changed over time," says Ben Sutlieff, an astronomer at the University of Edinburgh who co-led the study. But when they studied images from the European Southern Observatory's Very Large Telescope in Chile, they noticed something else in the data. "There's something else there, did you see it?" recalled Markus Bonse, an ESO astronomer in Germany and the study's other co-lead.
The team searched through old observations stored in the ESO archive and found that Beta Pictoris d had actually appeared in images going back more than 11 years — but no one had noticed it until now. "Planet d, it seems, has been playing a game of hide-and-seek with us for over a decade, and only now can we say 'found you,'" says Jayne Birkby, an astronomer at the University of Oxford and co-author of the study.
Beta Pictoris d is a gas giant like Jupiter or Saturn, but smaller. Scientists estimate it is 2.4 times more massive than Jupiter, making it one of the lightest exoplanets ever captured in an image from the ground. It orbits much farther from its star than the two other planets in the Beta Pictoris system, which are each about 10 times the mass of Jupiter.
An independent team at the University of California, led by Aidan Gibbs, also detected the same planet using the James Webb Space Telescope, confirming the discovery. The fact that two different groups using two different instruments found the same planet gives scientists extra confidence that it is real.
Direct imaging, which works like taking a photograph, only works for planets bright enough to stand out next to their much brighter host stars. Capturing a planet as faint as Beta Pictoris d is a genuine technical breakthrough. The team made the detection using an instrument called ERIS attached to the Very Large Telescope. For astronomers, this discovery shows that even well-studied cosmic systems can hold secrets — they just need the right tools and a second look.