What information provided evidence for the location of the sun in the galaxy?
1. observation of globular clusters
2. observation of elliptical orbits of planets around the sun
3. determination of the composition of stars within the galaxy
4. measurements of relative brightness of stars within the galaxy

it is to be noted that an alpha particle is an helium nucleus. so it contains 2 protons 2 neutrons and has a mass number of 4. when alpha decay particles are ejected from the nucleus it gets transformed into an atom which has atomic number less than 2 and a mass number less than 4.

an equation that could represent alpha decay is radium 226 decay of alpha particle forms radon 222.

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