Young transiting planets

目前还不清楚大质量气态巨行星是由直接的引力坍缩（收缩）形成的，还是首先由尘埃凝聚和固体核心的缓慢增长（增长）形成的，然后再吸积大气层；或者两条路是否都有可能。行星形成的时间尺度也尚不清楚，例如，在Myr内快速（通过直接引力坍缩）或在数十至数百Myr内缓慢（通过尘埃凝聚）。我们计划测量年轻行星的半径和平均密度——只有通过凌日技术才能直接测量。在目前已知的所有凌日行星（www.exoplanet.eu）中，没有一个比几百迈尔更年轻。我们计划继续并完成寻找年轻凌日行星的项目：我们在年轻的猎户座25星团中发现了一颗非常有希望的候选者，我们现在希望通过进一步的后续观测来确认它是最年轻的凌日行星。预期的结果将使我们能够对不同的形成情景（以及行星形成的时间尺度）给出约束，从而更好地理解行星形成的一般过程。

It is still not clear whether massive gas giant planets form by direct gravitational collapse (contracting) or first by dust coagulation and slow growth of a solid core (growing), then accreting an atmosphere; or whether both paths are possible. The time-scale of planet formation is also not yet known, e.g. fast within Myr (by direct gravitational collapse) or slow in tens to hundreds of Myr (by dust coagulation).We plan to measure radii and mean densities of young planets - possible in a direct way only with the transit technique.Among all transiting planets know so far (www.exoplanet.eu), none is younger than a few hundred Myr.We plan to continue and finish our project to search for young transit planets:We found a very promising candidate in the young cluster 25 Ori, for which we now would like to finish confirmation as youngest transit planet by further follow-up observations. The expected results would enable us to give constraints for different formation scenarios (and the planet formation time-scale) and, thus, lead to a better understanding of planetary formation processes in general.