The 2020 Nobel Prize in Physics has been awarded to three astrophysicists who made huge contributions towards our understanding of black holes. One half was presented to Roger Penrose for his proof that black holes result from general relativity, while the other half went jointly to Reinhard Genzel and Andrea Ghez for discovering the supermassive monster at the center of the Milky Way.
When Albert Einstein published his general theory of relativity in 1915, a particular solution to his field equations implied the existence of singularities where the laws of space and time cease to apply. For a while this was regarded as a mathematical curiosity rather than a description of a real object, even by Einstein himself.
But in 1965, Oxford professor Roger Penrose penned a paper demonstrating how black holes could form under realistic conditions, according to the equations set out in general relativity. The event horizon – the point at which even light cannot escape the black hole's gravitational pull – hides an infinitely dense singularity from the rest of the universe.
There’s a sad side to the story as well though. Penrose worked extensively with the late Stephen Hawking, who almost certainly would have shared in the accolade. Unfortunately, the Nobel committee doesn’t award prizes posthumously.
The other half of this year’s Nobel Prize in Physics was awarded to Reinhard Genzel and Andrea Ghez, who led teams of astronomers to independently conclude that there’s a huge mass at the heart of the galaxy, most likely a supermassive black hole. Ghez is only the fourth woman to win the Nobel Prize in Physics in its 120-year history.
Both teams examined the orbits of stars very close to this mass, in particular a star called S2, which orbits it in as little as 16 years. For reference, our Sun takes more than 200 million years to complete one lap. With such a short jaunt, the astronomers have been able to track S2’s entire journey.
From the results of the two teams, astronomers were able to calculate that the object at the center of the Milky Way has a mass about 4 million times that of the Sun. A supermassive black hole is the only explanation that fits the bill.
“The discoveries of this year’s Laureates have broken new ground in the study of compact and supermassive objects,” says David Haviland, chair of the Nobel Committee for Physics. “But these exotic objects still pose many questions that beg for answers and motivate future research. Not only questions about their inner structure, but also questions about how to test our theory of gravity under the extreme conditions in the immediate vicinity of a black hole.”
The announcement follows yesterday’s announcement of the 2020 Nobel Prize in Medicine to a trio of scientists for their work on the hepatitis C virus. Tomorrow the Nobel Prize in Chemistry will be announced.
Source: Nobel Prize organization
