Scientists work with astronomers from all across the world to better comprehend faraway galaxies

Artistic rendering of the BL Lac jet with a spiral magnetic field. Credit: Iris Nieh

A group of 86 scientists from 13 nations has conducted intensive high-resolution optical monitoring of BL Lacertae, a distant active galaxy (BL Lac). One of the astronomers involved in the experiment was Mike Joner, a BYU research professor of physics and astronomy. Dr. Joner and BYU undergraduate student Gilvan Apolonio obtained nearly 200 observations of the galaxy using the BYU West Mountain Observatory's 0.9-meter reflecting telescope. In a partnership known as the Whole Earth Blazar Telescope, these measurements were integrated with observations obtained by other scientists from across the world (WEBT). During periods of high unpredictability, the WEBT network allows for round-the-clock monitoring of items from various places.

Using WEBT data from the summer of 2020, researchers observed remarkably fast brightness fluctuations in the galaxy BL Lac's core jet. These cycles of brightness change are attributed to twists in the jet's magnetic field, according to scientists. Their findings were just published in Nature. West Mountain Observatory at BYU was one of 37 ground-based telescopes throughout the world that monitored the optical fluctuations of BL Lac, an active galaxy categorized as a blazar that is approximately 1 billion light years distant.

Throughout the spring and summer of 2020, Joner and Apolonio alternated working different groups of nights at the observatory, a duty that was made more difficult by the epidemic. This unusual work schedule was required since observations were required on every clear night and there were no other certified student observers in the Provo region. Understanding the high-energy data from the space-based Fermi Gamma-Ray Telescope required an examination of the high-cadence optical observations.

According to Joner, data from high-energy satellite observatories must be combined with optical ground-based monitoring data. The billion-dollar space telescopes employed in such programs frequently need to compare results to optical ground-based observations. Correlating what was seen in the high-energy observations with what was seen in the ground-based light curves helped substantiate the fast periodic oscillations detected in the high-energy data from space.

Despite his status as an acknowledged specialist in astrophysics study, Joner says he is still astounded by the degree of information scientists are recording through such observations. And he's glad for the opportunity to explore the outer reaches of the universe with his BYU students. A blazar's center jet is relatively modest on a cosmic scale. It's incredible to be able to observe the jet's fluctuations so vividly. Even though it is blended with light from hundreds of billions of stars in the host galaxy, the jet's fluctuation is plainly seen.

It is worth noting that, even in this day and age of huge telescopes and space-based research, it is still important to rely on modestly sized and well-equipped facilities like the ones we have at BYU to study the undiscovered depths of the cosmos.

Melissa Hallum, a Boston University doctorate student and previous student of Dr. Joner's, was also a co-author of the publication.