Weighing the Impossible

Weighing an object while it is billions of miles away may seem impossible, but scientists are still giving it a go.

Announced just this week, astronomers were able to measure the mass of Stein 2051 B, a white dwarf star about 18 light-years from Earth, using gravitational lensing.

Stein’s companion star, a bright red dwarf, passed behind the white dwarf. “During this transit, the background star appeared to change its position in the sky, moving ever so slightly to the side, even though its actual position on the sky had not changed at all,” according to an article by Scientific American. Using the Hubble Space Telescope, astronomers calculated how massive Stein 2051 B is by how much its companion’s light was deflected.

Gravitational lensing was first theorized by Einstein as part of his theory of general relativity. Einstein thought that objects bent space depending on their mass, and that massive objects could even bend and redirect light.

He also theorized that gravity could be used as a lens to magnify distant objects as massive objects bent light from the object towards the observer.

In 1919, British astronomer Arthur Eddington used a solar eclipse to show that the Sun’s gravity had displaced stars behind it.

The lensing effect Einstein thought about has also been tested. Massive objects can bend the light of objects behind them, creating an effect called an Einstein ring. This is especially helpful if the more distant object is smaller and fainter.

Doing the impossible has been science’s job for a long time now. Even though Einstein’s theories are now well-accepted and tested, but I hope this August’s solar eclipse will be a time to recreate Eddington’s experiment, among others.


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