天文現象及活動

2010年5月21日，日本宇宙航空研究開發機構開發的試驗性太空探測器IKAROS（Interplanetary Kite-craft Accelerated by Radiation Of the Sun = 依靠太陽輻射加速的星際風箏）。IKAROS 是世界第一個成功在行星際空間運作的太陽帆。該太陽帆的名字由日本航空太空工程師森治取名自希臘神話中的人物伊卡洛斯。
2010年12月8日，IKAROS 在距離金星 80,800 公里處飛掠過，並進入延伸任務階段。

【資料：維基百科】

相關流星群：天蠍-人馬座流星雨群組(SAG)

出現日期：
4月15日至7月15日
極大日期(香港時間)：
5月20日(星期六)9時09分
月閃高峰期：
遲0.2小時

天頂每時出現率ZHR：5顆
速度：每秒30公里(低速)
亮度指標：2.5(中等)

輻射點(曆元2000)：
赤經16.5時/247°赤緯-22°

有關今次天象更詳細資料請按左下角「外部連結」

http://forum.hkas.org.hk/thread-9675-1-1.html

物理系學生會議：銀河尺度內量子效應 – 模糊暗物質宇宙模擬及大尺度結構

Talk:- Quantum Effect in Galactic Scale: Fuzzy Dark Matter Cosmological Simulation and Large Scale Structure

The Ultra-Light Axion (ULA) is a dark matter candidate with mass o(10^-22) eV and de Broglie wavelength of order kpc. Such an axion, also called the Fuzzy Dark Matter (FDM), thermalizes via the gravitational force and forms a Bose-Einstein condensate. Recent studies suggested that the quantum pressure from the FDM can significantly affect the structure formation in small scales, thus alleviating the so-called “small-scale crisis”. We develop a new technique to discretize the quantum pressure and illustrate the interactions among FDM particles in the N-body simulation. With our highly efficient algorithm, the largest scale cosmological simulation of FDM model has been performed. The non-trivial effect of quantum pressure on Large Scale Structure (LSS) has been revealed. The constraints from recent Lyman-alpha Forest observations are discussed.　
　
時間：2017.05.20(六) 13:30 ~ 13:45
地點：香港中文大學 科學館LT4
講者：Jiajun Zhang
語言：英語

#131

此活動由香港中文大學物理系主辦。

宇宙中危機四伏，強烈的太陽風暴、不可抵禦的近地天體撞擊事件及來源不明的伽馬射線暴都有可能於一瞬間令地球上全人類滅亡。講者將會在是次講座中向觀眾解說各項危害背後的成因及科學原理。

時間：2017.05.20(六) 15:00 ~ 16:30
地點：香港太空館演講廳
講者：
●丘澄峰 (星匯點委員)
●梁家榮 (星匯點委員)

免費講座，歡迎公眾參加，座位先到先得

此活動由香港太空館主辦。

物理系學生會議：貝氏變分法到參數估算重力波天文學

Talk:- Variational Bayesian to Parameter Estimation in Gravitational Wave Astronomy

The traditional way of conducting parameter estimation in gravitational-wave data analysis is done by obtaining the posterior and evidence through Markov-Chain Monte Carlo methods. These computational methods are time consuming as they rely on wandering randomly in parameter spaces of high dimensions. Instead of randomly sampling, variational Bayesian makes use of an approximated probability distributions, which resembles the true distribution. Minimizing the differences between the true and approximated distributions can then be a more directional way of conducting parameter estimation. In this presentation, we will discuss the possibility of implementing variational Bayesian to parameter estimation in gravitational-wave data analysis.　
　
時間：2017.05.20(六) 14:00 ~ 14:15
地點：香港中文大學 科學館LT4
講者：Adrian, K.W. Chung
語言：英語

#131

此活動由香港中文大學物理系主辦。

13時31分，海王星合月，海王星在月球北0.47度

物理系學生會議：速旋中子星循雙曲軌道接近大質量黑洞之動力學

Talk:- Dynamics of Fast Spinning Neutron Stars in a Hyperbolic Orbit near a Massive Black Hole

The trajectory of a non-spinning test particle is given by the geodesics equations. However, when the test particle is spinning, it’s spin interacts with the orbit and the background curvature, giving rise to interesting dynamical behaviors, which in turn can probe the background space-time structure. In this research, we study a fast spinning pulsar orbiting in a hyperbolic orbit around a massive black hole. Millisecond pulsars are very accurate “clock” in the universe. Their abundant existence is predicted by various studies, which however, are not verified, due to the limit of pulsar timing techniques and the complicated pulse profiles of a accelerating pulsar. In this research, the spin problem in relativity and the dynamical features of such system were reviewed and studied. An orbital shift of ~100km and a velocity shift of ~1 km/s are observed, and the former will correspond to a shift of arrival time of pulse ~100μs, while the latter is related to the gravitational wave memory effect. The result of this study will provide useful insights for both the gravitational wave detector LISA, and the pulsar timing array SKA.　
　
時間：2017.05.20(六) 13:45 ~ 14:00
地點：香港中文大學 科學館LT4
講者：Jiale Kaye Li
語言：英語

#131

此活動由香港中文大學物理系主辦。

時間：2017.05.20(六) 17:00 ~ 18:15
地點：澳門科學館天文館
講者：龍嘉穎 Lydia Lung (天文匯)
語言：英語

免費活動，惟參加者必須於當日講座前先到售票處領取門票

#95

此活動由澳門科學館主辦。

時間：2017.05.20(六) 21:30 ~ 2017.05.21(日) 01:05
頻道：TVB 明珠台 CH084

#124

此活動由TVB Pearl主辦。

物理系學生會議：通過緻密雙星的重力波研究其潮汐變形能力 – 包含合併前階段的效應

Talk:- Studying the Tidal Deformability of Compact Stars Through Gravitational Wave from Binary Mergers: The Effect of Including Post-Merger Phase

The recent discoveries of binary black holes by gravitational-wave detection hint at the opportunity of detecting gravitational-wave signals from binaries consisting of compact stars. Binaries typically undergo three stages during coalescence: inspiral, merger and post-merger. Information on the compact stars’ matter is encoded throughout the gravitational-wave signal, detections of the signal can constrain the equation of state of ultradense matter. The feasibility of constraining the equation of state through gravitational-wave detections by second and future generation detectors have been studied using the inspiral and post-merger stages separately. We present the effect and the possible improvement in constraining the equation of state by using a toy model of binary mergers, which consists of inspiral and post-merger.　
　
時間：2017.05.20(六) 14:15 ~ 14:30
地點：香港中文大學 科學館LT4
講者：Peter, Tsun Ho Pang
語言：英語

#131

此活動由香港中文大學物理系主辦。