Planet formation around AGNs

Research Project

Project/Area Number	18K18774
Research Category	Grant-in-Aid for Challenging Research (Exploratory)
Allocation Type	Multi-year Fund
Review Section	Medium-sized Section 16:Astronomy and related fields
Research Institution	Kagoshima University
Principal Investigator	WADA KEIICHI 鹿児島大学, 理工学域理学系, 教授 (30261358)
Co-Investigator(Kenkyū-buntansha)	小久保英一郎国立天文台, 天文シミュレーションプロジェクト, 教授 (90332163)
Project Period (FY)	2018-06-29 – 2022-03-31
Project Status	Completed (Fiscal Year 2021)
Budget Amount *help	¥6,240,000 (Direct Cost: ¥4,800,000、Indirect Cost: ¥1,440,000) Fiscal Year 2020: ¥2,210,000 (Direct Cost: ¥1,700,000、Indirect Cost: ¥510,000) Fiscal Year 2019: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000) Fiscal Year 2018: ¥2,730,000 (Direct Cost: ¥2,100,000、Indirect Cost: ¥630,000)
Keywords	系外惑星 / 活動銀河中心核 / ダスト / 超巨大ブラックホール / 巨大ブラックホール / 重力多体系 / 銀河 / 惑星形成 / 星ダスト / ダスト成長 / 活動銀河核
Outline of Final Research Achievements	We found that a new class of planets, 'blanets' (i.e., black hole planets), can be formed from dust monomers around supermassive black holes (SMBHs) in the galactic center (Wada et al. 2019). We then investigated the dust coagulation processes and physical conditions of the blanet formation outside the snow line in more detail, especially considering the effect of the radial advection of the dust aggregates. We confirmed the necessary conditions for the blanet formation. The formation timescale of blanets is 70-80 million years for the SMBH mass of one million solar masses. The mass of the blanets ranges from 20 to 3000 Earth mass. Our results suggest that blanets could be formed around relatively low-luminosity AGNs during their lifetime (< 100 million years). The Discovery of blanets in external galaxies requires a breakthrough in observational technology.
Academic Significance and Societal Importance of the Research Achievements	惑星形成と超巨大ブラックホールというこれまでまったく無関係だった２つの研究分野が理論的に関連することが世界で初めて示され、天文学や物理学の応用性や理論天文学の手法の有効性を示すことができた。