Stars and planets through time

虽然我们已经探测到超过4000颗行星围绕着像我们的太阳这样的老主序星，但我们只发现了少数几个行星系统围绕着年龄小于几亿年的年轻恒星。然而，这些年轻的行星系统非常重要，因为它们直接将我们的行星形成和早期演化理论与较老的系外行星群联系起来。在这样做的过程中，他们为系外行星研究中一些关键的突出问题提供了重要的新见解。两个这样的问题是：（i）行星系统是如何形成和演变成我们观察到的多样化的人口？以及（ii）早期恒星活动如何影响随后的行星可居住性？

While we have detected over 4000 planets around old main-sequence stars like our Sun, wehave only discovered a handful of planetary systems around young stars with ages less thana few hundred million years. These young planetary systems are very important, however, asthey directly link our theories of planet formation and early evolution to the older exoplanetpopulation. In doing so, they offer important new insights into some of the key outstandingquestions in exoplanet research. Two such questions are: (i) how do planetary systems formand evolve into the diverse population that we observe? And (ii) how does early stellar activityaffect subsequent planet habitability?