Coldest Exoplanet Orbiting A Dead Star Found By Scientists

Using the James Webb Space Telescope (JWST), scientists have found the coldest exoplanet that is orbiting a dead star, also called a white dwarf. Named WD 1856+534 b, the exoplanet is a gas giant, located 81 light-years from Earth and sheds light on how planets evolve during the final stages of a star's life.

While the exoplanet was first spotted in 2020, an international team of researchers last week published their findings about it. Using the Mid-Infrared Instrument (MIRI) aboard the JWST, the scientists stated that temperatures reached a frigid -125 degrees Fahrenheit (-87 degrees Celsius), making it the coldest planet ever directly observed.

"We were all a bit surprised - and excited - to find that it was, in fact, a planet, and a really cold one at that," Mary Anne Limbach, an astronomer at the University of Michigan, who led the new study told Space.com.

The previous record for the coldest planet was held by Epsilon Indi Ab, which stands at around 35 degrees Fahrenheit (2 degrees Celsius).

"The detection of WD 1856 b, with its sub-200 K temperature, marks significant progress in directly detecting exoplanets with thermal emission similar in temperature to Solar System gas giants," the study highlighted.

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Life in forbidden zone

The researchers further confirmed that the exoplanet has a mass no greater than six times that of Jupiter and orbits the remnant core of a once sun-like star, every 1.4 days. Scientists added that it was the first intact exoplanet to have been found in the forbidden zone of a star.

"WD 1856+534 b is now the first intact exoplanet confirmed within a white dwarf's "forbidden zone," a region where planets would have been engulfed during the star's red giant phase. Its presence provides direct evidence that planetary migration into close orbits-including the habitable zone-around white dwarfs is possible."

Ms Limbach said their findings provide "compelling evidence" that not only can planets survive the violent death of their star but also move into orbits where previously they would have not expected them to exist.

Buoyed by the success, the researchers are hoping that JWST's full potential could be used to directly image even colder gas giants in closer systems with "temperatures as low as 75 K".

This capability could provide an opportunity to explore the atmospheres and thermal properties of planets with temperatures comparable to the coldest gas giants in our Solar System.