Extra-solar planet search using the Subaru Telescope

该研究项目旨在利用斯巴鲁望远镜日冕成像仪CIAO对100颗年轻恒星进行观测，以探测它们的星周结构和候选行星。CIAO是世界上大型光学红外望远镜中起步较早的一台。在过去的三年里，我们拍摄了大约80颗年轻恒星的图像，现在正在详细分析这些数据。以下是我们迄今取得的两项主要成果。(1)探测Aurigae AB周围原行星盘中的螺旋结构首次在年轻恒星Aurigae AB周围的原行星盘中发现了明显的螺旋结构。在原始太阳星云中，行星的形成始于尘埃粒子聚集成星子，随后它们碰撞并合并形成原行星，如果它们足够重，可以吸引周围的气体，原行星就可能成长为巨大的气体行星。在原行星盘中，类似的行星形成过程被认为更可能发生，其质量应该是其中心恒星的1%左右，并且引力稳定。因此，到目前为止，原行星盘被认为没有由引力不稳定引起的螺旋结构。螺旋结构表明，猎户座AB周围的原行星盘可能很重，以维持螺旋的不稳定性。如此重的圆盘可能会破碎，并遵循与太阳系不同的行星形成路径。(2)发现一颗质量为40木星的DH牛头伴星我们已经在观测到的年轻恒星中发现了20颗候选伴星，并正在进行后续观测，以判断它们是否是真正的物理伴星。在这个过程中，我们发现一颗靠近金牛座DH的恒星是一个物理伴星，质量是木星的40倍或太阳的0.04倍。因为行星目前被定义为质量小于木星13倍的伴星，我们的发现意味着对行星的直接成像现在几乎触手可及。少

This research program aims to observe one hundred young stars in order to detect their circumstellar structures and planet candidates with CIAO, a Subaru Telescope coronagraphic imager which started its operation early among the large optical-infrared telescopes in the world. We have imaged about 80 young stars for the last three years, now analyzing the data in detail. The followings are the two major results that we have achieved so far.(1)Detection of Spiral Structure in the Protoplanetary Disk around AB AurigaeA prominent spiral structure was for the first time discovered in the protoplanetary disk around the young star AB Aurigae. In the primordial solar nebula, planet formation begins with the accumulation of dust particles into planetesimals, followed by their collision and coalescence to form protoplanets, which may grow up to giant gas planets if they become sufficiently heavy to attract ambient gas. Protoplanetary disks within which the similar planet formation process is bel … More ieved to occur should have masses of order 1% of their central stars and be gravitationally stable. Protoplanetary disks are thus so far believed to have no structure such as spirals caused by gravitational instability. The spiral structure suggests that the protoplanetary disk around AB Aurigae might be heavy to maintain spiral instability. Such a heavy disk might fragment and follow a different path of planet formation than that occurred in our solar system.(2)Discovery of a 40 Juniter Mass Companion to DH TauriWe have detected 20 companion candidates among the observed young stars and are making follow up observations to judge whether or not they are real physical companions. During this process we have found that one star located close to DH Tauri is a physical companion with a 40 Jupiter masses or a 0.04 solar masses. Because planets are for the moment defined as companions with masses less than 13 Jupiter masses, our discovery means that direct imaging of planets is almost at hand now. Less