Dead planets can 'broadcast' their 'zombie signals' for almost a billion years, study

[Makuser]

Hi all. Well, with 14 of the last 16 days with thunderstorms and 2 power outages here in Florida, I am lately relegated to reading the great observing reports of others, reading and re-reading my astronomy magazines, and looking for interesting astronomy news for us to read. So here is another story.
Planets that have been dead for almost a billion years may still be able to "broadcast" their signals in space, according to a new study. According to research published in the Monthly Notices of the Royal Astronomical Society, planets that have been stripped down to their cores by their stars interact with that star (likely at the end of its lifespan and thus, a white dwarf) and send out radio waves, thanks to the magnetic field between the two celestial bodies. The radio waves are often picked up by radio telescopes on Earth. “There is a sweet spot for detecting these planetary cores: a core too close to the white dwarf would be destroyed by tidal forces, and a core too far away would not be detectable," the study's lead author, Dimitri Veras, said in a statement. "Also, if the magnetic field is too strong, it would push the core into the white dwarf, destroying it," Veras continued. "Hence, we should only look for planets around those white dwarfs with weaker magnetic fields at a separation between about 3 solar radii and the Mercury-Sun distance." It's still unclear how long the planetary cores can survive after the planet is stripped by the star. The researchers model dictates that in certain cases, the core can last for over 100 million years and perhaps as long as 1 billion years. You can read the entire report, and see the artist's rendering here, at:
https://www.foxnews.com/science/dead-pl ... lion-years