Astronomers have discovered a third planet circling the nearby star Beta Pictoris, using an instrument built in Edinburgh that has been described as the faintest world ever directly photographed from the ground.
The planet, named Beta Pictoris d, is roughly 100 times dimmer than Beta Pictoris b, the first planet found in the system. Despite its faintness, it ranks among the lightest exoplanets ever captured on camera from Earth.
The breakthrough came from the Enhanced Resolution Imager and Spectrograph, known as ERIS, mounted on the European Southern Observatory’s Very Large Telescope in Chile. At the heart of the instrument is an infrared camera called NIX, designed and built in Edinburgh by the Science and Technology Facilities Council’s UK Astronomy Technology Centre, working alongside colleagues at ETH Zurich and Leiden University. The wider British contribution to the research was also funded by the STFC.
An accidental find
The team had not set out to find a new planet at all. According to Dr Ben Sutlieff, an astronomer at the University of Edinburgh who co-led the study, the original goal was simply to track changes in the already-known Beta Pictoris b over time. It was only while reviewing the resulting images that the researchers spotted something unexpected, sending the investigation in a new direction. The findings appear in The Astrophysical Journal Letters.
Like Jupiter and Saturn, the newly found world is a gas giant, though at around 2.4 times Jupiter’s mass it is considerably lighter than the system’s two previously known planets. Beth Biller, Professor of Exoplanet Science at the University of Edinburgh, noted that directly imaged planetary systems often turn out to host several giant planets, and suggested further, lower-mass worlds may still be waiting to be found with future instruments.
Pushing the limits of the technique
Unlike most planet-hunting methods, which infer a planet’s presence from its gravitational tug on its host star, direct imaging captures light from the planet itself. Picking out something so faint beside a star so much brighter represents a significant technical achievement, according to William Taylor, an instrument scientist at the UK Astronomy Technology Centre, who said the discovery showcased what the NIX camera could do.
To verify the find, researchers combed through more than ten years of archived observations from ESO’s telescopes and traced signs of the planet as far back as 11 years. Oxford astronomer Jayne Birkby, also a co-author, likened the process to a decade-long game of hide and seek finally coming to an end.
A separate research group, led by Aidan Gibbs at the University of California, independently confirmed the planet’s existence using the James Webb Space Telescope. Both sets of results have been published together.
A rare multi-planet system
Sitting 63 light-years from Earth, Beta Pictoris is now known to host at least three planets, making it only the second system, after HR 8799, in which more than two planets have been directly photographed. Sutlieff said systems containing multiple directly imaged exoplanets are especially valuable, since they offer insight into how different types of planets can form within the same environment.
The discovery illustrates how modern instruments, paired with decades of archival astronomical data, can still reveal objects that had gone unnoticed for years.
Source: UKRI
