Astronomers directly imaged a third planet orbiting Beta Pictoris, a star 63 light-years away, after recognizing the world in observations spanning more than a decade. Named Beta Pictoris d, the gas giant is 100 times fainter than Beta Pictoris b and was reported as the faintest exoplanet yet directly imaged from Earth.
The discovery emerged unexpectedly from work intended to track changes in Beta Pictoris b. After the researchers noticed signs of an additional planet, they examined 11 years of archived images and identified the same object across the older material. The result ended a search in which the planet had remained hidden in the glare and complexity of the system.
Beta Pictoris d has an estimated mass about 2.4 times that of Jupiter. Its two known siblings, Beta Pictoris b and c, are each about 10 Jupiter masses. The new world is farther from the host star and consequently cooler than the other planets, as well as smaller than Beta Pictoris b. Those properties make its direct detection particularly demanding.
Direct imaging captures a planet’s own thermal glow against the much brighter light of its star. The contrast makes the method difficult: among more than 6,000 worlds in NASA’s exoplanet catalogue at the time, fewer than 100 had been found through direct imaging. Detecting a world as faint as Beta Pictoris d therefore extends the technique toward less massive and harder-to-see planets.
The planet may also resolve a longstanding question about the Beta Pictoris system’s disk of dust and debris, material thought to remain from planet formation. Researchers said the planet occupies the location and has the mass needed to account for both the disk’s position and its unusual shape.
With the additional detection, Beta Pictoris became only the second known planetary system in which more than two worlds had been directly imaged. HR 8799, about 133 light-years away, was the first. Multiple imaged planets in a single system give astronomers a way to compare worlds that developed in the same environment rather than studying isolated examples.
The finding also suggests that other well-known imaged systems may contain faint, lower-mass companions that current instruments have missed. Researchers pointed to the Extremely Large Telescope, under construction in northern Chile’s Atacama Desert, as a future tool for pursuing such objects.
The team’s research was published in The Astrophysical Journal Letters. Its significance rests not only on adding a planet to a nearby system, but also on demonstrating that careful reanalysis of long-running observations can reveal worlds far dimmer than the companions that first drew astronomers’ attention.
