摘要
2014年9月,智利北部阿塔卡马沙漠高原上新建成的阿塔卡马毫米/亚毫米波阵列(Atacama Large Millimeter/submillimeter Array,ALMA)进行了仪器测试,开展了持续的天文观测项目.ALMA是用干涉方法进行天文观测的射电天线阵,由66个天线构成,总长度达到16km.ALMA是一个国际合作建设的天文工程,由来自欧洲、北美和东亚等的各国(地区)合作运行.
The classical theory of planet formation can be traced back to the German philosopher Kant,who speculated that the Sun and the major planets were created in a cloud of faint gas and dust that gradually collapsed and flattened.In the theory,the planets are predicted to move about the Sun in low eccentric orbits and they are nearly coplanar.Nowadays,astronomers have developed this theory to further improve our understanding of planet formation process based on modern astronomical observations and high-speed computations.The widely accepted model of planet formation suggests that molecular clouds collapse to form the protostars in the central region,while the gas and dust remain in the protoplanetary disk surrounding young stars.In the subsequent process,the gas and dust in the protoplanetary disk can be further cooled down and gradually condensed into larger particles,then grow into planetesimals;the planetesimals can form planetary embryos through mutual gravitational interaction and frequent collisions,finally produce terrestrial planets and gas-giants.In this so-called core-accretion scenario,there exists a key issue to be first solved—the gas-giants such as Jupiter should be formed right before the protoplanetary disk entirely dissipates,because these gaseous planets,which initially start from a terrestrial core of a mass up to ten Earth masses,can only accumulate hydrogen and helium when the protoplanetary disk is still present.Based on observations of the protoplanetary disks and the age of young stars,the astronomers have shown that the lifetime of protoplanetary disks is roughly estimated to be 1–10 million years.This indicates that the formation process of gas-giants needs to be supremely fast.The entire formation scenario from the gas and dust in the molecular cloud to more than a dozen Earth mass planetary cores and then to the gas-giants should be completed in approximately 10 million years.In 2014,the ALMA(Atacama Large Millimeter/submillimeter Array)imaged the first protoplanetary disk around the
作者
季江徽
Jianghui Ji(CAS Key Laboratory of Planetary Sciences,Purple Mountain Observatory,Chinese Academy of Sciences,Nanjing 210008,China E-mail:jijh@pmo.ac.cn)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2019年第23期2369-2373,共5页
Chinese Science Bulletin
基金
国家自然科学基金(11773081,11661161013)
中国科学院空间科学战略性先导科技专项(XDA15020302)
中国科学院创新交叉团队项目
紫金山天文台小行星基金会资助
