Cosmic Kick: Warm Orphans Born from Stellar Death
Original: "Contribution of White Dwarf Formation Kicks to the Free-Floating Planet Population"
When a white dwarf is born, a gentle nudge can eject planets from the system, creating a unique class of warm free-floating worlds.
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White dwarfs, the quietly fading remnants of stars, are sometimes born with a tiny kick—just 0.75 km/s. That’s enough to turn a multi-planet system into chaos. Like ripples from a stone thrown into water, circles of instability spread: up to half of systems lose their worlds, casting them out into interstellar space. Still warm from bathing in the dying star’s rays, these planets become thermal beacons—ideal prey for future telescopes like Roman.
🎯 If the Sun turned into a white dwarf right now, Jupiter would heat up to 700 K—hotter than the surface of Venus—and would stay warm longer than human civilization has existed.
P(v_{\mathrm{kick}}) = \sqrt{\frac{2}{\pi}} \frac{v_{\mathrm{kick}}^2}{\sigma_{\mathrm{kick}}^3} \exp\left(-\frac{v_{\mathrm{kick}}^2}{2\sigma_{\mathrm{kick}}^2}\right)
Probability distribution of kick velocities with parameter σ ≈ 0.5 km/s and a peak near 0.75 km/s—essentially, how often and how hard the star “kicks” the system.
T(\tau) \approx \left( \frac{\eta G M_P^2}{2 \tau 4\pi R_P^3 \epsilon \sigma} \right)^{1/4}
Approximate cooling law, where η is a factor of order 0.01–0.03; τ is time; M_P, R_P are the planet’s mass and radius; ε is emissivity; σ is the Stefan–Boltzmann constant. It shows that the planet holds onto heat for a surprisingly long time.