No.242
2001.5

A Salute to Minoru Oda@@
‚h‚r‚`‚rƒjƒ…[ƒX@2001.5@No.242@@

- Home page
- No.242 –ÚŽŸ
- ¼”öO‹B
- “c’†–õ˜Y
+ Riccardo Giacconi
- ¼‘º@ƒ
- ŒIŒ´•¶—Ç
- ‰Z–{M“ñ
- ŽõŠx@
- ‹{–{dŒ›
- –쑺–¯–ç
- —с@—F’¼
- •½”ö–M—Y
- ˆäã_ŽO˜Y
- Œ´@G“¿
- –q“‡ˆê•v
- ˆäã@ˆê
- Ken Pounds
- •½ŽR@~
- X–{‰ëŽ÷
- ŒË“cN–¾
- Šâ“c•y”ü
- “Iì‘אé
- H—tè`“ñ˜Y
- ¼“c“čO
- ¬“c–«æ¶‡“¯‘’
- ISASŽ–î
- •ÒWŒã‹L

- BackNumber

Riccardo Giacconi@


@Those who knew Minoru Oda and his work will miss him as a scientist, a friend, and a wonderful human being.

@He was an outstanding scientist and teacher and, together with Satio Hayakawa and Yasuo Tanaka, one of the founders of space science in Japan, particularly x-ray astronomy. He was a man of great scientific curiosity and in his career he became involved with acoustics, cosmic rays, x-ray and radio astronomy, and, most recently, physiology of the brain.

@Our friendship and collaboration continued for almost forty years, but no one person can easily trace his accomplishments in such disparate fields. This is particularly difficult for me since much of his activity took place in Japan. I will describe only two episodes which were important to both of us.

@The first occurred in 1965 when Minoru was in the U.S. and invented the modulation collimator. He had been doing cosmic ray research with the MIT group led by Bruno Rossi in 1962 when our group at ASE discovered the first x-ray star, SCO X-1. He became immediately interested in this research and followed our rocket program closely.

@In the many discussions we had about the nature of x-ray stars it became clear that any known physical process that produced x-rays should also produce visible light. The optical plates of the sky near SCO X-1 showed no peculiar object. Could it be that the object was a diffused nebula? Then it could be so dim that it could not be observed. The only way to clear this mystery was to measure the x-ray size of the object. The best accuracy that could be obtained with the rather primitive instruments we then had available was too poor to decide this issue. Minoru's contribution was typical of his subtle and clever approach to the study of nature. The modulation collimator does not pretend to measure the position in the sky of a source (because of its multifold solutions) but it allows the measurement of angular size. In two ASE rocket experiments in 1965 and 1966, the angular size of SCO X-1 was measured to be less than 7 arc seconds. This result predicted a relatively bright star coincident with SCO X-1 position.

@This position was measured in 1966 by using two modulation collimators with the vermer technique devised by Herbert Gursky. There followed the discovery by Japanese and American astronomers of the optical counterpart of SCO X-1 which revealed a new class of objects. It is interesting to note that while these experiments were being done, Minoru succeeded in getting scientists at MIT to become involved experimentally in the ASE program and to arouse the interest of optical astronomers in Japan in following this subject.

@This ability to relate to the interests and aspirations of people of very different cultures was an outstanding gift that Minoru used again and again to foster scientific cooperation on an international scale.


G. Clark”ŽŽm‚Æ(ƒzƒƒCƒgƒ}ƒEƒ“ƒeƒ“C1968”N )

@The second episode that I briefly mention relates to the discovery of pulsations from the source Cyg X-1 with the Uhuru satellite. In 1971 the ASE group that conceived and built the satellite was frantically busy trying to keep up with the data stream that was flowing from it daily. The only outsider we invited to participate in the beginning phase of the interpretation was Minoru. This is a tribute to him as a scientist and as a trustworthy friend. Minoru became interested in observing strange temporal events that could not be easily reconciled with statistical fluctuations. He noticed that during a single pass of the satellite detector field of view on Cyg X-1 the number of counts registered seemed to vary too much to be explained by statistics. There followed the decision to slow down the satellite spin to afford more observing time for each source. We extended the observing time from a fraction of a second to 20 seconds and the measurement revealed that Cyg X-1 was wildly pulsating. It was the first stellar mass black hole ever discovered !


K-9M-31†‹@‚̏€”õ(1971”N‚WŒŽ)

@The observations at this reduced spin rate led shortly thereafter to the discovery of the class of x-ray binaries containing neutron stars or black holes.

@After his return to Japan Minoru worked hard to establish experimental x-ray astronomy at Tokyo University. His success is demonstrated by the world class group that is his legacy.

@I last saw Minoru for a short hour in Tokyo last year. He was, as usual, leaving for some meeting in Europe and I was in Japan to discuss possible Japanese collaboration with Europe and the US on the ALMA project in millimeter wave astronomy. Minoru was helping us overcome cultural barriers. A recently signed agreement in Tokyo makes this the first worldwide project in astronomy. I regret deeply that Minoru Oda will not be able to share the joy of first light.

(Associated Universities, Inc. )@


#
–ÚŽŸ
#
¬“c‚³‚ñ‚Ì‘z‚¢o
#
Home page

‚h‚r‚`‚rƒjƒ…[ƒX No.242 (–³’f“]Ú•s‰Â)