A nova remnant is made up of the material either left behind by a sudden explosive fusion eruption by classical novae, or from multiple ejections by recurrent novae. Over their short lifetimes, nova shells show expansion velocities of around 1000 km/s,[1] whose faint nebulosities are usually illuminated by their progenitor stars via light echos as observed with the spherical shell[1] of Nova Persei 1901[2] or the energies remaining in the expanding bubbles like T Pyxidis.[3]
^Liimets, T.; Corradi, R.L.M.; Santander-García, M.; Villaver, E.; Rodríguez-Gil, P.; Verro, K.; Kolka, I. (2014). A dynamical study of the nova remnant of GK Persei / stella novae: Past and future decades. Stellar Novae: Past and Future Decades. ASP Conference Series. Vol. 490. pp. 109–115. arXiv:1310.4488. Bibcode:2014ASPC..490..109L.