This fundamental constant of nature remains the same even near a black hole – Science News

Even on a black holes turf, anessential constant of nature holds steady.

According to standard physics, the fine-structureconstant, which governs interactions of electrically charged particles, is thesame everywhere in the universe. Some alternative theories, however, suggestthat the constant might be different in certain locales, such as the extremegravitational environment around a black hole. But when put to the test nearthe supermassive black hole at the center of the Milky Way, the number didnt budge, physicists report in a paper accepted in Physical Review Letters.

The fine-structure constant is one of anassortment of unchanging numbers found in physics formulas, such as the mass ofan electron or the speed of light. It determines the strength with whichelectrically charged particles pull on one another. Scientists dont know whyit has the value it does about 1/137. But its size seems crucial: If that number were much different, atoms wouldntform (SN: 11/2/16).

Using experiments on Earth, scientistshave previously shown that the fine-structure constant doesnt vary over time.Whats interesting here is to try to search for variation somewhere else inthe universe, in a totally different environment, says physicist Aurlien Heesof SYRTE at lObservatoire de Paris.

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Using observations of light from fivestars that cruise around the supermassive black hole at the center of the galaxy,Hees and colleagues searched for hints of an altered fine-structure constant. Whenthe starlight is separated into different wavelengths, it shows features calledabsorption lines, which indicate particular wavelengths of light that areabsorbed by certain atoms. If the fine-structure constant were altered at thegalaxys center, the separation between those absorption lines would differfrom measurements of those absorption lines made on Earth.

But the absorption lines agreed withexpectations. The researchers calculated that the fine-structure constant nearthe black hole agreed with its earthly value to better than a thousandth of apercent.

Its the first time scientists havesearched for a variation of the fine-structure constant in the general vicinityof a black hole, says Wim Ubachs of Vrije Universiteit Amsterdam, a physicistwho previously has searched for changes in various constants of nature.

A 2010 study gave tentative hints thatthe fine-structure constant might vary as scientists look farther outinto space, with the number increasing or decreasing in certain directions, but the evidence for that phenomenon is notconclusive (SN: 9/3/10). Soscientists are probing the constant in a variety of ways, including near ablack hole.

The work is very important because itdenotes the beginning of a new type of study, namely, searching for variationof the fine-structure constant at the center of the galaxy, says physicist JohnWebb of the University of New South Wales in Sydney.

In previous research, Webb andcolleagues found no variation while probing the fine-structure constant in an environment thatseven more gravitationally extreme: the surface of dense dead stars called whitedwarfs. So if the new research had found any indication of change in thesteadfast constant, Webb says, I would have been very surprised.

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This fundamental constant of nature remains the same even near a black hole - Science News