How do we have heavy elements like uranium on the earth?
Supernovas are claimed to be manufacturing center of the heavy elements in the universe.And usually the remnants of such massive supernovas are black holes.
AndCygnus X-1is the closest black hole to the earth which is at a distance of $6,100 \pm 400$ light years.
If we imagine a sphere which have radius equal to 6,100 light years.The surface area of the sphere is $37875166695400,000,000,000000,000,000,000~\mathrm{km^2}$.
While compared to that,the cross section of the earth is almost insignificant($142334130.878~\mathrm{km^2}$) as it is just $0.0000000000000000000000003758 \%$ of the imaginary sphere's surface area.
How could earth have such a large amount of uranium and other heavy elements in spite of it's negligible size?
Best Answer
There are many misconceptions in your question.
First: Most supernovae probably end up as neutron stars, not black holes.
Second: The nearest black hole is not CygnusX-1. It maybe the closest one we know about, but a simple calculation reveals that the nearest black hole is likely to be within 20pc and the nearest neutron star at about 10pc. https://astronomy.stackexchange.com/questions/16678/how-far-away-is-the-nearest-compact-star-remnant-likely-to-be
Third: The chemical elements that make up the Sun and Earth are the products of many millions of dead stars. Supernovae scatter elements into the interstellar medium, gradually enriching it with heavy elements. There are mixing processes that take place on timescales of billions of years that mean this material is effectively homogenised, and there is little metallicity gradient in the Milky Way near the Sun. We cannot identify ancestors of the solar system.
Fourth: There are chemical differentiation processes in the protoplanetary disc and the planet formation phase that ensure heavy elements are very much over-represented say compared with the Sun.
The solar system formed from an interstellar cloud with only about 2% elements heavier than Helium. Those heavier elements all come from around a 10 billion dead stars (supernovae, novae, AGB stars), though the Uranium is all produced in around a billion supernovae.