Physics
The Darkest Mysteries of the Cosmos are Revealed
The Strangest Objects in the Universe are Finally Acknowledged by the Nobel Committee
I’m feeling overjoyed upon hearing the news about the Nobel laureates this year. The reason behind my excitement is that this year’s prize has finally been awarded in my own research field i.e specifically in the advancement of our understanding of black holes. I cheerfully pay my heartiest congratulations to the brilliance of these geniuses.
It’s a moment of excitement for all the astronomy and astrophysics community. Because there is a long-running joke about awarding prizes in astronomy and astrophysics that the Nobel community doesn’t bother about these observational subjects.
In these fields, it was last awarded in 2006 “for their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation” and in 2011 “for the discovery of the accelerating expansion of the Universe through observations of distant supernovae”. Now it’s been two years in a row, in 2019 “for the discovery of an exoplanet orbiting a solar-type star and for theoretical discoveries in physical cosmology” and now finally in astronomy for long-running mysteries i.e black holes in 2020.
The Royal Swedish Academy of sciences has decided to present One half of the Nobel prize share to Roger Penrose for the theoretical prediction of black holes assumed in Einstein’s general theory of relativity. While the other half jointly to Reinhard Genzel and Andrea Ghez for their discovery of the supermassive black hole in the center of our own MilkyWay (our universe’s darkest secret).
Background and Current Affiliation of the Nobel-Trio
- Roger Penrose came to St John’s college in 1952 as a grad student and completed his doctoral dissertation on tensor methods in algebraic geometry, in 1957. He is now an emeritus professor at the Mathematical Institute at the University of Oxford, United Kingdom. Also, he is an honorary fellow of St John’s College, Cambridge, and University College London (UCL).
- Andrea Ghez was an undergrad student at MIT and she completed her doctorate from Caltech in 1992. Including Andrea, MIT has now become home to 102 Nobel laureates. She is the fourth woman to be awarded Nobel Prize in Physics, after Marie Curie in 1903, Maria Goeppert-Mayer in 1963, and Donna Strickland in 2018. She asserted, “It amazes me every time I go to the telescope.” Andrea Ghez is currently affiliated with the University of California, Los Angeles.
- Reinhard Genzel studied early physics at the University of Freiburg. He completed his doctorate in physics and astronomy at the University of Bonn in 1978. His dissertation was about radio astronomy at the Max Planck Institute for Radio Astronomy at Bonn. Genzel is currently serving as co-director of the Max Planck Institute for Extraterrestrial Physics, Germany. Also, he is a professor at Ludwig Maximilian University, Munich, and an emeritus professor at the University of California, Berkeley.
How singularities arise?
Now let us have a review of the structure and geometry of these cosmic beasts in detail. In 1915, Albert Einstein wrote the tensor equations that describe the motion of matter and its effect on the surrounding celestial bodies. He wrote them by making two torsion-free quantities i.e Einstein tensor and matter tensor, proportional to each other. One side of the equation tells us about the matter distribution and the other side corresponds to the geometry.
The first-ever solution to these highly non-linear equations was derived by Karl Schwarzschild in 1916, with few assumptions. That solution consisted of both essential and removable singularities.
Hence, the solutions of Einstein’s field equations predicted the presence of singularities in the universe. But, we know mathematics fails to cope with singularities or infinities as there is no physical meaning they have.
If anything aims to enter inside a black hole, it is doomed forever. Not even the signals of light are capable enough to reach back to us, that’s why they are named black. Time and space cease to exist inside them.
The concept of their existence is so bizarre and extreme that even Einstein had doubts about it. In 1939, he wrote a paper in Annals of Mathematics and deduced that the idea of black holes was not so convincing.
A Brief Explanation of Their Work
Roger Penrose wrote a ground-breaking paper with the late Stephen Hawking in 1970. They presented in that paper a new generalized theorem on spacetime singularities which revolutionized our understanding of spacetime. They proved that if our universe obeys Einstein’s general theory of relativity and Friedmann’s models about the universe, then there is essentially a singularity at the beginning. According to the Nobel Prize website:
“Penrose used ingenious mathematical methods in his proof that black holes are a direct consequence of Albert Einstein’s general theory of relativity.”
This time the Nobel prize is awarded for theoretical and observational discoveries. The theoretical work was being done in the 1970s by the legends Stephan Hawking and Roger Penrose, and it was observationally proved in the 21st century. They used Einstein’s general theory of relativity and proved the singularity theorems i.e the existence of a point in space-time where the gravitational pull is so strong that even light could not escape. These were just mathematical manipulations at that time but now it’s a truth in front of us.
Now it’s an obvious question to ask why they both didn’t receive Nobel prize when we knew the black hole’s existence for so long. The answer to this is the Nobel community likes a theory to be experimentally or observationally verified. For example, Einstein predicted the existence of gravitational waves in 1916 and the Nobel community awarded them in 2017 upon their detection. This year it is awarded because we finally have received the incredible image of a supermassive black hole in the center of M-87 the previous year. It was brought to light by a huge collaborative team of the EHT (Event Horizon Telescope).
Now one can wonder why not the prize is shared between the EHT team and Roger Penrose. Well, it is hard to swallow but it’s the policy of Nobel that the prize is only shared between three people and not the entire collaboration.
Professor Genzel and Andrea Ghez both have done an incredible job to answer the biggest mystery that lies inside our MilkyWay galaxy. They were observing stars near the galactic center using high-resolution infrared telescopes.
Infrared light has a long wavelength than visible light, which means it’s not blocked by tiny particles of interstellar dust in the space. We can’t see the center of our galaxy with visible light but with infrared light. Hence, in this way, one can measure the position and speed of stars locating near the center of the MilkyWay, then work out the orbits of those stars and the influence of gravity around them, after that one can calculate the mass of the central object to speculate the size of that object at the center.
In 1969, Donald Lynden-Bell and Martin Rees have put forward a suggestion that our home galaxy might contain a dense, compact supermassive black hole at its core. But there was no way to verify that because the core of the galaxy was always hidden behind gases and interstellar dust.
At that time Genzel was working as a post-doctoral fellow at UC Berkely with the late Charles Townes who was a Nobel laureate. His collaborator asserted that he presented a “remarkable technique, in which he can measure very accurately and determine quite precisely the mass and behavior of stars circulating around the galactic center.”
Together with this technique and the ground-based telescopes at ESO (European Southern Observatory) i.e NTT (New Technology Telescopes) located in Chile, they observed the motion and position of ten stars for about four years from 1992 to 1996. They collected data and modeled the orbits of those stars and derived the mass of a central object as about 2.45 million times the mass of the Sun. But that was just one result and hence can not be generalized at that time.
Observation by Genzel’s research group about the stars orbiting the galactic center also confirmed the predictions of Einstein’s general theory of relativity; that the orbit of a star follows a flower-like pattern (perihelion shift) while orbiting a massive object.
Andrea Ghez has done that with much more precision with her team the galactic center group at UCLA. With more high-resolution W.M. Keck observatory’s telescopes in Hawaii, they observed the interstellar medium and dust around the supermassive black hole i.e Sagittarius A*.
They used adaptive spectroscopy, more precisely the laser technology to avoid turbulence which disrupts the light under observation in the atmosphere. They removed all kinds of turbulence and noise from their data. They observed more than 3000 stars for 12 years from 1995 to 2007. Finally, they obtained the result of the mass of a central object to be 4.5 million times the mass of the Sun. She also studied the dynamics and interactions between the stars. That observation again confirmed the previous result that a dense compact supermassive black hole resides in the galactic center.
The amazing work done by both independent teams has been recognized by royal Swedish academy of sciences. They said it “has given us the most convincing evidence yet of a supermassive black hole at the center of the Milky Way.” Keck Observatory Director Hilton Lewis admired Ghez as “one of our most passionate and tenacious Keck users.”
Andrea has been acknowledged by many people from MIT in very kind words. Nergis Mavalvala said,
“All of her careers, Andrea has been an awe-inspiring scientist, educator, and a role model for women and girls. And now, as a Nobel laureate, her groundbreaking science, and her story are sure to reach even farther and inspire a generation of young women to pursue careers in science.”
In the announcement, the chair of the Nobel Committee David Haviland added in appreciation that,
“The discoveries of this year’s laureates have broken new ground in the study of compact and supermassive objects. 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.”
Thank you for reading this story and see you again. Feel free to leave a comment if you have any thoughts, feedback, or suggestions about it!
