Unexpected discovery of cold planet in the 'forbidden zone' of space

The white dwarf star WD 1856+534, 82 light-years from Earth in the constellation Draco, is 5.8 billion years old - Photo: NASA Goddard Space Flight Center

Astronomers have made a groundbreaking discovery by confirming the existence of an icy planet orbiting a white dwarf star in a region of space known as the "forbidden zone" - where planets normally cannot exist.

The white dwarf star WD 1856+534, located 82 light-years from Earth in the constellation Draco, is 5.8 billion years old. In 2020, NASA's TESS satellite, along with several ground-based observatories, discovered an object the size of Jupiter orbiting the star every 1.4 days.

Recently, a research team led by Dr. Mary Anne Limbach of the University of Michigan used the James Webb Space Telescope to confirm that the object, named WD 1856+534b, is indeed a planet. Notably, the planet is located very close to its host star, 30 times closer than the distance between Mercury and the Sun.

When low- to medium-mass stars like the Sun run out of nuclear fuel, they swell into red giants before expelling their outer layers and leaving behind a dense core – known as a white dwarf. Typically, planets within a radius of two astronomical units, or the “forbidden zone”, are destroyed in the process, scientists say.

By analyzing signals received from the James Webb telescope, researchers determined that WD 1856+534b has a mass about 5.2 times that of Jupiter and a surface temperature of -52 degrees Celsius, making it the coldest exoplanet ever observed in direct light.

However, it is still not the coldest known planet, as the planet OGLE-2005-BLG-390Lb near the center of the Milky Way has a surface temperature of about -223 degrees Celsius.

Scientists believe that WD 1856+534b originally had a more distant orbit and moved into the "forbidden zone" after its host star stabilized as a white dwarf, possibly due to the gravitational influence of another planet or star.

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Source: https://tuoitre.vn/bat-ngo-phat-hien-hanh-tinh-lanh-gia-trong-vung-cam-vu-tru-20250514091849874.htm