RADIO ASTRONOMY — HAWKINS 



289 



posed of methane and ammonia and contains clouds at a temperature 

 of —140° C, while the planet itself is presumed to be formed of solid 

 ices, again at a low temperature. Other noises that have been 

 recognized are grinding sounds and rumbles. When analyzed in de- 

 tail these sounds are apparently composed of a series of two or three 

 pulses following one another in rapid succession. 



**fP%^.-^ 





GALACTIC CENTER -f 



THIS REGION NOT 



YET MAPPED 



SCALE 



Figure 4. 



30,000 



LIGHT YEAR8 



-Spiral structure of the local galaxy. (Reproduced by permission of G. Wester- 

 hout and M. Schmidt, Leiden, Holland.) 



By an ingenious method it has been found possible to locate the 

 area which is generating the noise. The transmission is spasmodic, 

 some days it is present, other days it is absent, but by observing over 

 long periods of time the noise has been found to vary in synchronism 

 with the rotation of the planet. This defines a north-south line, or 

 line of Jovian longitude on which the source lies. The planet's speed 

 of rotation, as given by observations of clouds in the atmosphere, 



