With gravitational forces powerful enough to warp space-time, black holes are considered among the most mysterious and alarming things in the universe.
This semester at Northern Kentucky University, a guided research course was created for a group of physics students with a specific interest in black holes. Sharmanthie Fernando, a professor with an extensive record of publications on black hole physics, designed a course to theoretically study massless and massive particles orbiting black holes immersed in dark energy.
With graduate-level material, this course provides students with a passion for black holes the unique opportunity to work with a professor who has several years of experience with black hole physics research.
“We are trying to work towards a publication that the world can read,” Kevon Reis, physics major and part of Fernando’s research course, said. “That’s how the physics field gets expanded. People work on something, other people get inspired…Then it get’s expanded on and expanded on.”
The Research
Although Fernando typically takes on one student at a time for research, the high amount of interest prompted her to plan a class for multiple students to take part this semester. Fernando designed the guided research course to allow three students at different levels in their physics studies to develop the skills to tackle the complex mathematics involved in studying black holes.
“You have to want to know about it, and you have to want to learn about it a lot,” Jonathan Wright, physics major and student in the class, said. “The mathematics behind it are kind of dizzying.”
This course introduces the students to geodesics and other aspects of differential geometry that students typically see in graduate school in order to study various black hole models. The students utilize a computer software, Mathematica, to understand the geometry of the massive and massless particle orbits and solve equations with answers that might end up being over a page long.
As part of the course, Reis, Wright and Scott Meadows were assigned to study different models of black holes immersed in dark energy. Their three projects examined the differences between the orbit of photons around a charged black hole, the orbit of massive particles around a neutral black hole and the orbit of massive particles around a charged black hole.
“Even the slight changes change just drastically over these different types of models,” Reis said.
Such studies are significant to comprehending and interpreting astrophysical observations of orbits in the future because the galaxies and planetary systems are considered to be formed by particles moving in circular orbits around an attractive center, according to Fernando.
“There is a lot to [NKU’s physics program] if you look for it, go out and seek it,” Reis said. “To be able to come to such a small program and study things like this, I think it is absolutely just amazing.”
In addition, some of the projects lead to publication. In the past, Fernando and her research students have published several papers on black hole research in well-established journals.
Next school year, Fernando plans to to write a paper with Reis and Meadows on the research they conducted this semester.
More recently, Fernando worked with Juan Correa, a senior physics major, and published their research titled “Quasi normal modes of Bardeen black holes: scalar perturbations” in 2012.
Black holes “oscillate just like a vibrating string does,” and when this happens specific types of frequencies called quasi-normal frequencies are produced, according to Fernando. Quasi-normal frequencies have “implications on observations of black holes.” For this project, they computed the quasi-normal frequencies for one black hole class.
“We really don’t know what is going on with black holes,” Correa said. “We have so many models and theories that need to be tested.. It is just really rewarding being able to come up with different models and apply them and see if they are going to work.”
With 32 publications concerning black holes and General Theory of Relativity, Fernando has become an expert in her field of research. Last year alone, she published five papers on the subject.
She is always looking for new projects to work on by herself or in collaboration with NKU students, according to Fernando. Currently, she is writing a book on black hole physics.
This theoretical research and collaboration is important to black hole examinations in the future. Black hole studies have been “a major component in the current research community working on gravitational physics and particle physics,” according to Fernando.
Although scientists cannot directly observe black holes, it is possible to infer their presence and learn more by studying their effect on different matter.
“So, if we are able to observe a black hole, we can rule out what kind of behavior it is not doing because of the things we have already done with general relativity,” Wright said.
What is a black hole?
Although the name seems to describe an empty area, black holes consist of a massive amount of matter packed into a very small region of space. Recent observations suggest that black holes are at the center of many, if not all, galaxies, according to Fernando.
“No one knows what these things are,” Reis said. “We don’t even know what the inside is. We know that mass just collapses, but what goes on inside the black hole?”
This still image was taken from an artist’s animation of energy escaping a black hole. Scientists at NASA’s Goddard Space Flight Center say this black hole spins and pumps energy out through cable-like magnetic field lines into the chaotic gas whipping around it, making the gas — already infernally hot from the sheer force of crushing gravity — even hotter.
A black hole can be thought of as “a star 10 times more massive than the sun squeezed into a sphere approximately the diameter of New York City,” according to NASA’s website. Nothing, including light, can escape the strength of its gravitational field.
Through his theory of general relativity, Albert Einstein predicted the existence of black holes in the universe. The theory describes black holes as an end-state for massive stars. They are formed when a massive star runs out of fusible material and collapses with nothing holding back the gravitational force.
Some stars are so massive that gravity “crushes and compacts the material down to a smaller and smaller volume and continues compacting until it has no volume,” according to Wright. This process continues until the dead star’s mass exists in an infinitely small point called a singularity.
“The math physically fails [at the singularity],” Reis said.
The gravitational force is so powerful near the singularity that light cannot escape. The area around the singularity is called an event horizon. Since no light can pass through it, it appears black. Anything that crosses the event horizon is trapped and can never return.
“It is quite literally trapped inside,” according to Reis.
Dark Energy: A Mystery
Though roughly 70 percent of the universe is made up of dark energy, many theoretical black hole models exclude its presence.
As a relatively new phenomena, “there is much to do in terms of understanding the structure of black holes immersed in a universe with dark energy,” according to Fernando.
“Dark energy is so important because it is believed to explain why the universe is accelerating,” Wright said. “They think it is absolutely crucial.”
Scientists were aware that the universe was expanding. However in 1998 they realized it was not only expanding, it was accelerating, and there had to be some form of energy causing that.
“It turns out that when we add the dark energy [into the model], it more or less changes the geometry,” Reis said.
Despite making up most of the universe, dark energy remains a mystery.
