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Do white dwarfs harbor habitable "zombie" planets?

Posted: Tue Sep 08, 2020 8:21 pm
by brian livesey
The possibility of white dwarfs having habitable planets orbiting them, but have not been discovered because nobody has looked for them, has been proposed by Thea Kozakis at Cornell University, New York - New Scientist ( page 46 ) August 29 issue.
Kozakis points out that the heat radiation from a white dwarf remains constant for billions of years, although habitable planets would need to be much closer in to their star to get the benefit of the relatively feeble heat. The orbits of the planets would also need to be circular, otherwise there would be enormous tidal changes.
The article seems to miss out an important point. As we know, a white dwarf is the exposed core of a star that passed through a red giant stage. Presumably, any inner planets would have been vaporised and/or roasted, and any outer planets would ( presumably ) have been stripped of their atmospheres. Kozakis says that white dwarf planets should be detectable by their transiting of the star, they could cause a 4O per cent reduction of the starlight as seen from Earth.