Symmetrical cosmic objects have been found to be sources of gamma radiation.

Compact Symmetrical Objects (CSOs) are small active galaxies characterized by unusual "miniature" jets that extend no more than a thousand light-years. So far, astronomers have identified only three CSOs that emit gamma rays. However, an analysis of archival observations from the LAT gamma telescope revealed that the previously classified as an uncertain type blazar, galaxy DA 362, is actually the fourth CSO emitting in the gamma range.

2025-01-07 14:10:21https://naked-science.ru/article/astronomy/simmetrichnye-kosmicheski

Streams of electrons, charged ions, and other particles burst forth from the vicinity of supermassive black holes, believed to reside at the centers of nearly all galaxies, extending thousands and even millions of light-years. In comparison, the relativistic jets emitted by active galactic nuclei (AGN), characterized by intense radio emission, are merely tiny (less than a thousand light-years).

Despite their modest size, these jets exhibit symmetry: when observed in the radio range, they can be seen ejecting in both directions from the center almost like a mirror image. Astronomers believe that AGN are either very "young" (only a few thousand years old) or that their jet growth is hindered by a dense surrounding medium. The nature of these objects has been explained by researchers previously.

Now, scientists from the Inter-University Center for Astronomy and Astrophysics in Pune (India) have classified the galaxy DA 362 as a subclass of AGN, confirming its gamma-ray emission with 95 percent accuracy. Before this, the object was thought to be a blazar—an active galaxy whose jets are directed toward the observer. The research has been accepted for publication in the journal The Astrophysical Journal.

By analyzing multi-wavelength data collected by the LAT gamma-ray telescope over the past 15 years, astronomers observed a stable background gamma-ray emission from DA 362, as well as a gamma-ray flare (10 times exceeding the average) that occurred around 2020-2021. This is a unique phenomenon for AGN: the three previously detected objects—TXS 0128+554, NGC 3894, and NGC 6328—did not exhibit such "flares."

The authors of the study also noted that during the first 12 years of the LAT telescope's operation, DA 362 was in a quiescent state, and the later-detected flare indicates gamma-ray emission coming from the jet or core (not from the radio lobes of the AGN).

Results also showed that when transitioning to other wavelengths, the fourth AGN behaves unusually: it is virtually invisible in the optical and ultraviolet ranges (possibly due to dust obscuration), unlike in the infrared range, where the object stands out brightly. Spectral analysis of the gamma-ray properties of DA 362 (and its comparison with three other AGN) revealed that the fourth is the brightest object and has a softer gamma spectrum.

This rare source of gamma-ray emission raises new questions about the formation and evolution of active galaxies in the early stages of their development. Further study of DA 362 will allow astronomers to determine the exact cause of this AGN's powerful gamma-ray emission. Possible causes, according to the authors, may include jets erupting from the center at near-light speed or intense star formation.