Grant-in-Aid for Scientific Research (A).
|Allocation Type||Single-year Grants |
|Research Institution||Nagoya University |
MURAKI Yasushi Solar-Terrestrial Environment Laboratory, Nagoya University, Professor, 太陽地球環境研究所, 教授 (70013430)
MASUDA Kimiaki Solar-Terrestrial Environment Laboratory, Nagoya University, Associate Professor, 太陽地球環境研究所, 助教授 (40173744)
MATSUBARA Yutaka Solar-Terrestrial Environment Laboratory, Nagoya University, Associate Professor, 太陽地球環境研究所, 助教授 (80202323)
ABE Fumio Solar-Terrestrial Environment Laboratory, Nagoya University, Associate Professor, 太陽地球環境研究所, 助教授 (80184224)
NAKAMURA Takashi Yukawa Institute for Theoretical Physics, Kyoto University, Professor, 基礎物理学研究所, 教授 (80155837)
SAKO Takashi Solar-Terrestrial Environment Laboratory, Nagoya University, Research Associate, 太陽地球環境研究所, 助手 (90324368)
佐藤 文隆 京都大学, 理学部, 教授 (90025370)
|Project Period (FY)
1999 – 2000
Completed (Fiscal Year 2000)
|Budget Amount *help
¥16,400,000 (Direct Cost: ¥16,400,000)
Fiscal Year 2000: ¥7,600,000 (Direct Cost: ¥7,600,000)
Fiscal Year 1999: ¥8,800,000 (Direct Cost: ¥8,800,000)
|Keywords||gravitational microlensing / Magellanic cloud / black hole / extra-solar planet / EAGLE event / long-period variables / dark matter / difference imaging analysis / 重力レンズ / CCDカメラ / 地球型惑星 / ガンマ線バースト / 星の大量連続測光|
It is now well known that the Universe is filled with 'dark' matter. In order to investigate dark matter in the form of black holes and small low luminosity stars as well as to detect extra-solar planets, we have set up the MOA collaboration together with astronomers in New Zealand. We use the phenomenon of gravitational micro-lensing to detect such objects by observing the variations of the brightness of field stars produced by intervening dark, massive objects. See http : //www.vuw.ac.nz/scps/moa/.
To date we have observed 4.4 million stars in the Large Magellanic cloud, 930 thousand stars in the Small Magellanic Cloud and 5.9 million stars in the bulge of our own galaxy. As a result of these observations, which have involved the analysis of enormous amounts of data by our group, we have :
1) discovered a very interesting event in which the light intensity from a star increased over a period of 80 days, suggesting (with 40% probability) that a black hole was involved ;
2) found indicati
ons for the presence of one or even two Earth-sized planets close to a lens star and published the results in the Astrophysical Journal (this may be the first observation of such small planets and was given wide publicity in New Zealand and Japanese news media - radio TV and newspapers) and have shown that most planetary systems do not contain Jupiter-like planets ;
3) developed a new method of data analysis based on a differential imaging technique which has been used since May 2000 to issue alerts of possible candidates for micro-lensing events to the world-wide astronomical community. This has been much appreciated since the MACHO collaboration stopped their alerts in 1999 and only MOA can observe the Large Magellanic Cloud in winter time ;
4) have found examples of so-called EAGLE events, which differ from the usual gravitational lensing by their sharply-rising light curve, and which provide greater sensitivity for dark matter and planet detection.
5) confirmed the existence of the overtone pulsators in Mira variables in the Large Magellanic Cloud and are now examining their nature together with appropriate magnitude and color calibrations.
In future, in order to obtain much better information on the dark matter problem and to learn more about extra-solar planets and their formation, it will be necessary to introduce a 1.5 metre, f=4 telescope into the program. Less