'Bent light' from distant star proves Einstein right 100 years later
Einstein predicted that the space-warping gravity of stars could also bend starlight itself.
Eric MackContributing Editor
Eric Mack has been a CNET contributor since 2011. Eric and his family live 100% energy and water independent on his off-grid compound in the New Mexico desert. Eric uses his passion for writing about energy, renewables, science and climate to bring educational content to life on topics around the solar panel and deregulated energy industries. Eric helps consumers by demystifying solar, battery, renewable energy, energy choice concepts, and also reviews solar installers. Previously, Eric covered space, science, climate change and all things futuristic. His encrypted email for tips is email@example.com.
ExpertiseSolar, solar storage, space, science, climate change, deregulated energy, DIY solar panels, DIY off-grid life projects. CNET's "Living off the Grid" series. https://www.cnet.com/feature/home/energy-and-utilities/living-off-the-grid/Credentials
Finalist for the Nesta Tipping Point prize and a degree in broadcast journalism from the University of Missouri-Columbia.
Just over a century after Albert Einstein managed to grok how the universe works without the aid of the fancy algorithms and space telescopes we have today, modern astronomy and technology has again issued an "I told you so" on his behalf.
Einstein's General Theory of Relativity predicts that the gravity of stars acts as a kind of magnifying glass for other more distant stars when a nearer star passes in front of them. This is because the gravity of huge objects like stars actually causes the fabric of space to curve around them.
Einstein surmised that as light from more distant stars passed by, it too would be curved or bent by the foreground star's gravity, but observing this effect would require a near perfect alignment of two stars from the vantage point of Earth.
"When a star in the foreground passes exactly between us and a background star," Terry Oswalt of Embry-Riddle Aeronautical University explains, "gravitational microlensing results in a perfectly circular ring of light -- a so-called 'Einstein ring.'"
Some evidence of the effect came in 1919 when curving starlight could be measured around a solar eclipse, but observing light bending around a star beyond our own solar system was a far greater challenge. In 1936, Einstein wrote in the journal Science that he felt there was no hope of ever observing the phenomenon directly.
However, on Wednesday, a new study published in Science provides the first evidence of Einstein's "gravitational microlensing" by a star other than our sun. Using the Hubble Space Telescope, an international team led by Kailash C. Sahu of the Space Telescope Science Institute measured the deflection of light from a distant star as it passed in front of a nearby white dwarf star called Stein 2051 B several times over a two year period.
While the two stars weren't in perfect alignment, they were close enough that the asymmetrical version of an Einstein Ring that the astronomers observed still demonstrated the bending of light Einstein had predicted.
This allowed them to measure the mass of Stein 2051 B and determine what the star is made up of, which has been a long-standing mystery for scientists. In an article accompanying the study in Science, Oswalt notes that mass is "the single most important property of a white dwarf star."