LIFE IN THE UNIVERSE — ^HUANG 



247 



Phenomenon 



11.9-YEAR REVOLUTION 



Maximum Effect 



0.01 KM./SEC. 



Figure 3. — Three kinds of observational tests are presented for the detection of a planet 

 similar to Jupiter revolving around a solar-type star 32 light-years distant from us. 

 Even at best, the maximum effects (right) are very minute. 



it were associated with the nearest star, for the planet would be lost in 

 the glare of the star's light. However, as Nancy G. Roman has sug- 

 gested, a telescope installed in an artificial satellite would suffer much 

 less from scattering of starlight in the earth's atmosphere and might 

 be used for such a search. 



What theoretical reasoning can be applied to this problem ? Some 

 30 years ago astronomers felt that our solar system was formed when 

 the sun encountered another star. Since the average distance between 

 two neighboring stars is very large, a close encounter of this kind is 

 a very rare event, producing only one planetary system among many 

 millions of stars. But it has since been shown that the collision theory 

 of planet formation is untenable. 



Astronomers are now convinced that planets form from dust and gas 

 that is either the remnant in the process of star formation or that has 

 been acquired from the interstellar medium. If the cloud is massive 

 enough, another star could be formed instead of planets. Thus, binary 

 and planetary systems have apparently the same origin, and they have 

 other properties in common. 



According to G. P. Kuiper, the average separation of all com- 

 ponents in binary systems that have been studied is about 20 astro- 

 nomical units, roughly the mean distance of the major planets from the 

 sun. Also, there is wide range in the ratio of masses of binary star com- 

 ponents, with a few as small as 10 times the ratio of Jupiter's mass to 

 the sun's. Unseen companions with masses about 0.01 that of the 

 sun have been found by K. A. Strand (61 Cygni) and Sarah Lee Lip- 

 pincott (Lalande 21185). Since binary stars are very numerous, 

 planetary systems should also occur frequently. 



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