Three laureates share this year’s Nobel Prize in Physics for their discoveries about one of the most exciting phenomena in the universe, the black hole.
Roger Penrose, Emeritus Rouse Ball Professor of Mathematics at the University of Oxford, showed that Einstein’s theory of relativity leads to the formation of black holes. He shared the prize with Reinhard Genzel, a German astrophysicist, and Andrea Ghez, an American astronomer, who discovered that an invisible and extremely heavy object, possibly a supermassive black hole, governs the orbits of stars at the centre of our galaxy.
David Haviland, chair of the Nobel Committee for Physics, said that this year’s discoveries have “broken new ground in the study of compact and supermassive objects”.
The first clues about the concept of black holes came from British scientist John Michell who noted in 1783 that light cannot escape from objects that are extremely massive given their size.
In 1915, Albert Einstein unveiled his general theory of relativity which describes how massive objects cause a distortion in space-time. This is felt as gravity causing trajectories of freely falling objects to curve like Earth’s elliptical orbit around the Sun, the theory states. Einstein himself, however, never believed in the possibility that black holes could exist. In a 1939 paper, he said the idea was “not convincing” and that the phenomena did not exist “in the real world”.
Twenty years later, Indian astrophysicist Subrahmanyan Chandrasekhar found that when a star much more massive than the Sun exhausted its fuel it would collapse indefinitely, seeding the possibility of the formation of a singularity. Gravitational singularities are locations where physical laws are indistinguishable from one another, and where space and time cease to have any independent meaning.
This brings us to January 1965, ten years after Einstein’s death, when Roger Penrose proved that black holes can really form, describing them in detail. His groundbreaking article is still regarded as the most important contribution to the general theory of relativity since Einstein.
Speaking to Oxford University, Penrose said: “’It is a huge honour to receive this Prize. In 1964 the existence of black holes was not properly appreciated. Since then they have become of increased importance in our understanding of the universe and I believe this could increase in unexpected ways in the future.”
Reinhard Genzel and Andrea Ghez, who together shared half of the 10 million Swedish kronor prize money, each lead a group of astronomers which focused on a region called Sagittarius A* at the centre of our galaxy since the early 1990s.
The orbits of the brightest stars closest to the middle of the Milky Way have been mapped with increasing precision. The measurements of both groups both found extremely heavy, invisible objects that pull on the jumble of stars, causing them to rush around at dizzying speeds.
Around four million solar masses are packed together in this region which is no larger than our own solar system.
Genzel and Ghez used the world’s largest telescopes to see through the huge clouds of interstellar gas and dust to the centre of the Milky Way.
They also found ways to compensate for distortions caused by the Earth’s atmosphere during their long-term research. Their pioneering work has given us the most convincing evidence yet of a supermassive black hole at the centre of the Milky Way.
On being the fourth female Nobel Laureate in Physics, Andrea Ghez said: “To me it’s always been very important to encourage young women into the sciences, so to me it means an opportunity and a responsibility to encouraging the next generation of scientists who are passionate about this kind of work into the field.”
On her inspiration to become an astrophysicist she added: “I think it’s a passion for the universe. It amazes me every time we go to the telescope to think about ‘here is this light that we’re capturing that’s been on a journey for 26,000 years’.”
“And you know, if you think about 26,000 years ago when these photons left the vicinity around the black hole it’s just … it’s rather amazing to think we can do this as human beings.”