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Astronomy Astrophysics

A Stellar Corpse and its Survivor Child

Can a child ever get older than its parents? Right, the answer is a ‘No’. But a child can outgrow its parents in size. Do you agree?

An illustration of WD 1856 b orbiting the parent White Dwarf
Credit: NASA’s Goddard Space Flight Center

This is what a team of international astronomers has recently discovered in a Stellar Family using NASA’s TESS and the old buddy- Spitzer Space Telescope, before it was decommissioned earlier this year. TESS discovers exoplanets by scanning the large parts of the sky. It does so by observing the dimming in the light coming from a star as the planet, during its revolution, passes in front of its star and blocks the star’s light. Spitzer, however, operates in the Infrared region of the Spectrum.

The team has found a 14xJupiter Mass planet called WD 1856 b revolving around a white dwarf, named WD 1856+534 about 80ly away in the constellation of Draco. The white dwarf is just 40% bigger than the Earth in size. The discovery is startling because the planet orbits the star 60 times as fast as Mercury orbits the Sun once. The Planet, being so close to its parent, is intact and is suspected to have survived the fierce death of its parent star.

The white dwarfs are the dense cores of the dead stars, having masses of order of the mass of the Sun. When a Sun-like star gets older and older, it runs out of fuel and reaches the red giant phase of its life where it grows bigger and bigger in size and enlarges hundreds to thousands times of its original size. Eventually, the red giant puffs off its outer layers of gas forming a planetary nebula and what remains is the hot dense core. Any nearby planets or bodies are usually engulfed by the star during its red giant phase.

Past researches and studies have provided evidence for inward scattering of asteroids and comets after the formation of the White Dwarf. They are then shattered by white dwarf’s strong gravity and form a debris disk around it. What has surprised astronomers the most is that the planet WD 1856 b remained intact even if it had made an inward journey. The statement “So far, no intact planets have been detected in close orbits around white dwarfs. Here we report the observation of a giant planet candidate transiting the white dwarf WD 1856+534 (TIC 267574918) every 1.4 days.” was published in an article on September 16, 2020 on Nature.

The team has suggested several possible explanations for this to happen. One reason could be that the planet, WD 1856 b, got nudged inwards due to many Jupiter-sized bodies which might lie closer to its original orbit. Another reason, for the inward push, could be the gravitational tug of the two other red dwarfs which are a part of the WD 1856 system. Perturbation of the whole system due to a flyby from a rogue star could also be a possible reason. But according to the team, all these explanations are merely theories and even they are awaiting the confirmed explanation to reason this.

The Universe is bigger than we can ever imagine and is full of surprises for us to discover. The explanations can go as wild as the Universe wants them to be. And we believe that the explanations can be as bizarre as possible provided the laws of Physics do not break. A possible explanation, I really do not know if it is correct, that came in my head was that the planet was initially a rocky body which accreted all the gas and material, puffed off by the star as it became a white dwarf, onto it. So, what are your possible explanations? Let me know in the comments below.


[1] Potter, Sean. “NASA Missions Spy First Possible ‘Survivor’ Planet Hugging White Dwarf.” NASA, NASA, 15 Sept. 2020, www.nasa.gov/press-release/nasa-missions-spy-first-possible-survivor-planet-hugging-white-dwarf-star.

[2] Wall, Mike. “Big Find! Scientists Spot Giant Alien Planet Orbiting Close to Dead Star’s Corpse.” Space.com, Space, 16 Sept. 2020, www.space.com/giant-exoplanet-found-orbiting-white-dwarf-wd-1856b.html.



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