2025-04-30T19:50:34Z

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Astronomers utilizing the advanced capabilities of the James Webb Space Telescope (JWST) have made a groundbreaking discovery, directly detecting the faint glow emanating from an exoplanet that is astonishingly colder than any other world whose light has been previously observed. This remarkable finding sheds light on the extreme conditions that exist on some planets in our vast universe.

The exoplanet in question, named WD 1856+534 b, was initially identified back in 2020. This intriguing celestial body is estimated to be twice as old as our solar system, which dates back approximately 4.6 billion years. WD 1856+534 b is comparable in size to Jupiter but has a mass about six times greater, and it resides in a frigid environment, boasting an average temperature around -125 Fahrenheit (-87 Celsius). Such a temperature makes it the coldest exoplanet ever detected through its own emitted light. The findings detailing this exoplanet's characteristics and thermal emission have been made accessible to the scientific community and the public via the preprint server arXiv.

Unique to WD 1856+534 b is its orbital relationship with a white dwarf, which is essentially the remnant core of a star that has exhausted its nuclear fuel and shed its outer layers. This relationship is significant because it facilitated the detection of the planet; typically, when stars are bright, they obscure the dim light of their orbiting planets. However, the white dwarf that WD 1856 b orbits is dim enough that the glow of the exoplanet could be discerned by the sensitive instruments aboard the JWST. Notable contributions to this research have come from astronomer Mary Anne Limbach, affiliated with the Department of Astronomy at the University of Michigan.

Perhaps most intriguingly, WD 1856 b resides in a rather unusual orbital vicinity, lying just 0.02 astronomical units from its white dwarf star. For context, this distance is closer than Mercury's orbit around our own Sun. The scientific team has labeled WD 1856+534 b as the first confirmed intact exoplanet residing in what is referred to as a white dwarf's 'forbidden zone.' This term describes a region where planets would have typically been consumed during the star's earlier red giant phase. The implications of this finding are substantial; it suggests that planetary migration into close orbitspotentially even into the habitable zonesaround white dwarfs is not only plausible but may indeed occur.

In the larger context of exoplanet research, this discovery positions WD 1856 b at the forefront of the cold world hierarchy. Previously, Epsilon Indi Ab held the title of the coldest imaged exoplanet beyond our solar system, with an estimated temperature of around 35 degrees Fahrenheit (2 degrees Celsius) when studied by JWST just last year. In stark contrast, WD 1856 b's much lower temperature highlights the unique atmospheric and environmental conditions that can exist on planets orbiting dead stars.

Furthermore, this research helps resolve a prior ambiguity surrounding WD 1856 b's classification. Previously, there were speculations that it might be a low-mass brown dwarf. However, with its confirmed low temperature and revised mass estimatescapping at no more than 5.9 times that of Jupiterit has now been officially categorized alongside the thousands of exoplanets cataloged by scientists over the past few decades.

Overall, this study not only demonstrates the JWST's remarkable capability to investigate cold, mature planets but also serves as a poignant reminder that even those worlds orbiting the remnants of dead stars can still emit light, albeit faintly. This discovery opens up new avenues for understanding planetary systems and their formation in the universe.