Wesley Stine, Copy Editor
LIGO, the Laser Interferometer Gravitational Observatory, made news earlier this year with the first detection of a gravitational wave. This signal, from the collision of inspiraling black holes, originated roughly 1.3 billion light years away. Now, Ph.D. student Marek Szczepanczyk, under supervision of Dr. Michele Zanolin and other faculty of Embry-Riddle Aeronautical University, is leading an effort to pick up a gravitational signal much closer to home.
Szczepanczyk completed his bachelor’s and master’s degrees at the University of Warsaw, Poland. He started working on gravitational waves while still in Europe, and is now in the third year of his Ph. D. program, as well as his third year with LIGO. He currently serves as chairman of the LIGO group working on core-collapse supernovae.
There are several other people in ERAU working with gravitational waves, including faculty members Dr. Michele Zanolin, Dr. Andri Gretarsson, Dr. Brennan Hughey, and Dr. Sergio Gaudio as well as undergraduate students Jasmine Gill, Sophia Schwalbe, Marina Koepke, and James Pratt. Visiting master’s student from Rome, Martina Muratore, is also involved.
“We’re searching for gravitational waves from core-collapse supernova,” Szczepanczyk said. “When a star is burning, it burns fuel from hydrogen up to iron, and becomes like an onion, with many shells. You have the iron core, then you have silicon, then you have lighter and lighter elements outside”.
“When the iron core exceeds roughly 1.5 solar masses, it collapses under itself, and the core shrinks from 1000 km down to 20 km… right after collapse, it becomes a proto neutron star. Most of the energy goes with neutrinos, and the rest (around one percent) mostly goes into optical energy. Only a tiny bit is converted into gravity waves,” according to Szczepanczyk.
Szczepanczyk explained how the resulting signal is nine orders of magnitude weaker than the inspiral signal that was announced in February, and is thus detectable only over a much shorter range. “People were expecting the inspiral signal to be detected first… it’s more energetic, much more energetic. [But] we expect that if a supernova were to explode in our galaxy, we might see something…. Our range is the Local Group, up to 20 megaparsecs.” (For comparison, the signal detected in February was 400 Mpc away).
Astronomers expect supernova to occur in the Milky Way galaxy at a rate of one or two per century. However, according to Szczepanczyk, “If a supernova were to explode in our galaxy, we expect only a ten percent chance that we would see it with the naked eye.”
Galactic gas and dust obscure most light sources within the Milky Way, including supernovae, making them invisible from earth in the optical band. The most recent supernova visible to the naked eye was observed by Kepler in 1604. However, modern instruments allow the detection of the otherwise-hidden supernova because “Gravity waves and neutrinos can be seen through the dust,” Szczepanczyk explained.
As to the chances of success, Szczepanczyk describes his project as “like a gamble…. It may happen or it may not happen for the next few years. There are many different models of gravitational wave emission, and right now we are working on constraining the emission models. With the extreme models, we could see supernovae far away outside our galaxy, but with the conservative ones not too far.”
“When Galileo built his telescope,” Szczepanczyk concluded, “he saw new objects, and astronomy has changed. Now, with gravitational wave interferometers, we are able to see new objects. This is new gravitational wave astronomy.”