Lyttleton’s binary star theory was put forward to answer certain questions regarding the Russel’s binary star theory. He assumed that the radius of the orbit of the companion star was about 2,700 million kilometres.

According to his theory, the mass of the companion star was almost equal to that of the sun. He also presumed that the period of the companion’s revolution around the sun was about 50 years while the speed was about 10 km. per second. The speed of the intruding star round the sun was supposed to be about 32 km. per second.

According to Lyttleton’s theory the minimum distance between the sun’s companion and the intruding star was supposed to be 5 to 6 million kilometres. The passing star was too distant from the sun to cause formation of any filament on the latter.

It is difficult to understand why a filament in the intruding star could not be produced by the tidal attraction of the sun’s companion star.

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Another question is the escape of the sun’s companion into space. According to W.M. Smart, this required the conversion of its elliptic orbit into a hyperbolic one.

The question remains as to why and how did the companion star leave sun’s company but its filament remained in the gravitational field of the sun?

“Lyttleton, however, showed that within comparatively wide limits pertaining to the initial conditions this course of events was possible; the companion and the intruding star would disappear into galactic space and some parts, at least, of the filament would move in elliptic orbits around the sun”. (W.M.Smart).

Out of the filament planets would be formed. In the early stage, the planets were expected to pass close to one another and then they were in a fluid state. Tidal action between them would cause the formation of satellites.

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Criticism:

The planets are assumed to have originated in the zone of the filament close to one another and far from the sun. What has brought about the present spacing of the planets? This is one of the major drawbacks and as such, the binary theory of Lyttleton is no better than the theories which preceded this hypothesis.