Fred Hoyle & Geoffrey Hoyle's "Rockets in Ursa Major" (novel, space opera): Humanity with its long lost cousins fights off alien raiders

This started out as a disappointment because of expectations mismatch: I was expecting a hard sf novel by the author of "The Black Cloud"; it turned out to be a free-wheeling space opera by his son, Geoffery. Fans of Fred Hoyle will be disappointed.

As space opera, it's an ok read though nowhere near top league.

Story summary.

Earth is not the home world of humanity. Eons ago, when our ancestors began ruthless colonization of galaxy from wherever their home world was, few alien races could stop them. Until they came across Yela.

Yela have an ultimate weapon. They can cover an oxygen world in a layer of hydrogen, then somehow set the two to react - setting the world on a grand fire! They drove humans from all inhabited worlds & turned them into galaxy's brigands - always on the run. That was some 100,000 years ago, but galaxy is still an enemy of humanity.

50,000 years back, one of their groups was shipwrecked on earth & stranded. We are descended from these.

Now, the earth bound humanity has began exploring the galaxy, unaware of old antagonism. Aliens now know of earth as a human world, & are coming to raid.

This is the story of long lost cousins of humanity coming to aid of earth men against the aliens. Two together will repel the raiders ... for the moment at least. By deploying a super-bomb - drop some tonnes of Lithium near a sunspot on Sun's surface to generate a flare big enough to hurt supremely advanced aliens but with little damage to earth!!!

See also.

1. Michael Shaara's "All the Way Back": Another story share the basic idea of why galaxy is antagonistic to humanity.
2. Arthur Clarke's "Reunion": "Spacefaring humans originated elsewhere in galaxy" is an old meme. This Clarke story is one of the better examples of it. I initially read it as a somewhat racist story, but I now think better of it.

Fact sheet.

First published: 1969.
"Based on the play of that title by Fred Hoyle" "for presentation at London's Mermaid Theatre in 1962".
Rating: B.
Related: Stories of Fred Hoyle.