Relatively fascinating
Gravitational waves, black holes and the search for dark energy
L AST Saturday marked the one-year anniversary of the announcement of the discovery of gravitational waves, actual ripples in the fabric of the space/time continuum.
At the time, the announcement rocked the scientific world. Not only did it prove Albert Einstein’s general theory of relativity, it gave scientists a new tool to study things like black holes, neutron stars and supernovas.
Since then, the Laser Interferometer Gravitational Wave Observatory (LIGO) — twin labs in Washington and Louisiana — have detected another set of gravitational waves. In both cases, the waves were created by the collision of black holes more than 1 billion years ago.
Recently, University of Texas astrophysics professor Karl Gebhardt sat down with the Houston Chronicle to talk about his work, which focuses on both black holes and dark energy.
His work on black holes has helped build the case that a class of medium-mass black holes exists in between the stellar-mass black holes that result when massive stars explode as supernovae and the supermassive black holes that lie at the hearts of galaxies.
He also is one of the architects of HETDEX, the $34 million Hobby-Eberly Telescope Dark Energy Experiment. The project seeks to understand dark energy, the mysterious force causing the universe’s expansion to speed up.
Gebhardt graciously agreed to detour a bit from the conversation about his fascinating work and discuss the implications of the gravitational wave announcement one year ago.
Q So what has the discovery of gravitational waves meant for science?
A For me, it’s one of the top scientific discoveries of all times. There’s evolution, DNA/RNA, general relativity. It’s up there.
I can’t stress this enough: What we’re doing with gravitational waves is interacting with space. We knew gravitational waves existed. We had measured those. But we’ve never interacted with space itself. It’s a new way to interact with the fundamental component of the universe and where that will lead to... who knows?
In a thousand years, they will be talking about the day it was announced. It’s that important.
Q How has the discovery of gravitational waves changed the study of black holes? Has it changed?
A Not yet, but it will. There’s a caveat in there. It’s the mass of the black hole that they had discovered which was really interesting because there were very few predictions to find a black hole with a mass in that range. That’s what caught everyone off guard. So we’re up to two solid detections and one semi. The word on the street is there another pile in the can, something like 10-15 is the number I’ve heard tossed out there.
But it’s the mass range that’s interesting. We know of black holes that are about the mass of the sun. We know of black holes that are in the middle of the galaxy that are about a million times the mass of the sun. These were about 50 times the mass of the sun and that is kind of hard to make.
It’s not a surprise that you would find some of the more massive ones because they are easy to detect. But these are different.
Q I know there are some significant upgrades that have happened recently with the LIGO detectors. How will that change things?
A That will be huge! That will be phenomenal. What they’ll do is increase the sensitivity by a factor of about a two and a half that will increase how much you can observe because it goes by a volume by a factor of 10. So they should increase their numbers by a factor of 10. So yeah, that’s what we’ve all been waiting for.
I am expecting a flood of data in the next six months or so … I really want to use McDonald facilities for some of the follow-up studies. We have a new instrument called VIRUS, which I would argue is the most ideal instrument in the world right now because most of the telescopes when they do follow-ups are going to take an image of something that fluctuates, something that got bright and dimmed.
With our instrument that we’re building now, VIRUS, you can get spectra and tell how far away the object is and then you can pinpoint, because you have that information from gravitational waves, and you can pinpoint location that much more accurately.