Constraining a possible time-variation of the gravitational constant through “gravitochemical heating” of neutron stars

A hypothetical time-variation of the gravitational constant G would produce gravitochemical heating of old (_ 107−8 yr) neutron stars. It could produce detectable thermal ultraviolet emission from such stars for changes as small as |G˙ /G| ∼ 10−12 yr−1 , comparable to the best existing upper limits from other methods.