PSR B1620-26 PSR B1620-26 PSR B1620-26 is a binary star system located at a distance of 3,800 parsecs (12,400 light-years) in the globular cluster of Messier 4 (M4, NGC 6121) in the constellation of Scorpius. The system is composed of a pulsar (PSR B1620-26 A) and a white dwarf star (WD B1620-26 or PSR B1620-26 B). As of 2000, the system is also confirmed to have an extrasolar planet orbiting the two stars. The double system ("triple" including the substellar companion) is just outside the core of the globular cluster. The age of the cluster has been estimated to be about 12.2
Unit distance graph find a unit distance graph "G" in which some pair of vertices are at distance "A" in all unit distance representations of "G" . This result implies a finite version of the Beckman–Quarles theorem: for any two points "p" and "q" at distance "A", there exists a finite rigid unit distance graph containing "p" and "q" such that any transformation of the plane that preserves the unit distances in this graph preserves the distance between "p" and "q" . The full Beckman–Quarles theorem states that any transformation of the Euclidean plane (or a higher-dimensional space) that preserves unit distances must