White dwarf compared to Earth size. Image credit: Ohio State University/Richard Pogge

White dwarf compared to Earth size. Image credit: Ohio State University/Richard Pogge

Our Sun will eventually have the ultimate fate of becoming a white dwarf surrounded by gaseous remnants of its former life. White dwarfs are called "skeleton stars", no longer developing. What if solar systems with Sun-like stars still survive? What happens to these planets?

First, how close is that planet? For Earth, if we don't get engulfed in our own Sun when it goes into its Red Giant stage, we would have to endure intense solar winds as it transforms from Red Giant to barely the size of Earth in a matter of seconds! For our Sun in reality, Earth would very much get destroyed. Planets out by Jupiter and beyond are considered "safe."

Then, once our Sun has gone through those stages, the orbits of such planets would be in a bit of a chaotic mode then settle, first going outward due to tidal pressures from the Red Giant phase, then slowly inward as the white dwarf resumes smaller gravity. 

The current research involving detecting such planets around white dwarfs include three main questions:

1- How far out does a planet need to orbit to escape engulfment, and what happens to its orbit as the star evolves?

2 -What happens to a planet that survives engulfment? Under what conditions might it survive?

3- Suppose an Earth or super-Earth is detected in the habitable zone of a white dwarf. What are the chances that it is actually habitable instead of a burnt-out cinder?

 The fate of planets around a white dwarf star. Image credit: Figure 4 from "On the Orbits of Low-Mass Companions to White Dwarfs and the Fates of the Known Exoplanets" by Nordhaus and Spiegel, Monthly Notices of the Royal Astronomical Society

The fate of planets around a white dwarf star. Image credit: Figure 4 from "On the Orbits of Low-Mass Companions to White Dwarfs and the Fates of the Known Exoplanets" by Nordhaus and Spiegel, Monthly Notices of the Royal Astronomical Society

Thank you for reading and come back March 26th for highlights from the 49th Lunar and Planetary Science Conference!