https://arstechnica.com/science/201...ingly-right-as-researchers-weigh-white-dwarf/ The gravitational lensing effect predicted by General Relativity has become one of the most powerful tools in Astronomy. As detailed in "Einstein's Telescope" by Evalyn Gates, the Hubble Space Telescope has become one of the most powerful instruments in astrophysicist's toolbag because it is capable of doing interferometry on the multiple images of the same object caused by gravitational lensing. An international team of astrophysicists recently had a problem with the calculated age of Stein 2051 B, which appeared to be unreasonably light for a white dwarf star which is known to be bereft of the fusion process that produces iron. In order to be as light as originally calculated, Stein 2051 would have had to be quite old, on the order of the age of the universe. The problem presented itself this way. If you know the mass and the temperature of a white dwarf star, you can predict its radius, and also its age. If a white dwarf is too close to its neighbor (a binary star system), this analysis is in practice quite difficult to do. Enter Hubble's gravitational lensing interferometery upgrade. When four of the gravitationally lensed images of another star eclipsed by Stein 2051 B were compared to the predictions of General Relativity, the mass of Stein 2051 B was placed at 0.67 times the mass of our own Sun, making it a typical white dwarf star in every respect, and especially with respect to its calculated age. Some of the researchers registered annoyance at the continued unreasonable reliability of the predictions of General Relativity. Einstein's telescope remains the most powerful tool available for doing basic astronomy.