The recent GAIA DR2 measurements of distances to galactic novae have allowed to re-analyse some properties of nova populations in the Milky Way and in external galaxies on new and more solid empirical bases. In some cases, we have been able to confirm results previously obtained, such as the concept of nova populations into two classes of objects, that is disk and bulge novae and their link with the Tololo spectroscopic classification in Fe II and He/N novae. The recent and robust estimates of nova rates in the Magellanic Clouds galaxies provided by the OGLE team have confirmed the dependence of the normalized nova rate (i.e., the nova rate per unit of luminosity of the host galaxy) with the colors and/or class of luminosity of the parent galaxies. The nova rates in the Milky Way and in external galaxies have been collected from literature and critically discussed. They are the necessary ingredient to asses the contribution of novae to the nucleosynthesis of the respective host galaxies, particularly to explain the origin of the overabundance of lithium observed in young stellar populations. A direct comparison between distances obtained via GAIA DR2 and maximum magnitude vs. rate of decline (MMRD) relationship points out that the MMRD can provide distances with an uncertainty better than 30%. Multiwavelength observations of novae along the whole electromagnetic spectrum, from radio to gamma rays, have revealed that novae undergo a complex evolution characterized by several emission phases and a non-spherical geometry for the nova ejecta.

最近的 GAIA DR2 对银河系新星距离的测量使得我们能够在新的、更可靠的经验基础上重新分析银河系和外部星系中新星群的一些特性。在某些情况下，我们已经能够证实之前获得的结果，例如将新星群分为两类物体的概念，即盘状新星和核球新星，以及它们与 Fe II 和 He/N 新星中托洛洛光谱分类的联系。 OGLE 团队提供的最近对麦哲伦星云星系中新星发生率的可靠估计已经证实了归一化新星发生率（即宿主星系每单位光度的新星发生率）与颜色和/或类别的依赖性。母星系的光度。银河系和外部星系的新星发生率已从文献中收集并进行了批判性讨论。它们是评估新星对各自宿主星系核合成的贡献的必要成分，特别是解释在年轻恒星群中观察到的过量锂的起源。通过 GAIA DR2 获得的距离与最大幅度与下降率 (MMRD) 关系之间的直接比较表明，MMRD 可以提供优于 30% 的不确定性的距离。对新星从无线电到伽马射线的整个电磁频谱的多波长观测表明，新星经历了复杂的演化，其特征是几个发射阶段和新星喷射物的非球形几何形状。