Radio images of the sky have revealed hundreds of “baby” and supermassive black holes in distant galaxies, with light from galaxies scattering around in unexpected ways. Galaxies made up of huge cosmic bodies, thousands of light-years in size, gas, dust, and stars (like our Sun).
Given their size, you would expect that the amount of light emitted from a galaxy would change slowly and continuously, much later than a person’s lifespan. However, our study, published in the monthly notices of the Royal Astronomical Society, found a surprising population of galaxies whose light changed more rapidly in a few years whose light changed more rapidly.
What is a radio galaxy?
Astronomers believe that most galaxies have a supermassive black hole at the center. Some of these are “active”, meaning they emit large amounts of radiation.
Their strong gravitational fields pull them apart from the places around them, tearing them apart to form a hot plasma rotating donut called an “attraction disc”.
This disk orbits a black hole at almost the speed of light. Magnetic fields accelerate high-energy particles from disks from long, thin currents or “jets” along the rotating axis of a black hole. As they grow further from the black hole, these jets explode in large mushroom-shaped clouds or “lobes”.
This whole structure forms a radio galaxy, so it called because it shuts off a lot of radio-frequency radiation. It can be thousands, thousands or even millions of light years and so it can take regular time to show dramatic changes. Astronomers have long questioned why some radio galaxies host many lobes, while others remain small and limited. Two theories exist. One is that jets held by dense material around black holes, often known as frustrated lobes.
However, the details surrounding this incident remain unknown. It is not yet clear whether the lobes temporarily confined by a small, extremely dense environment – or if they are gradually enlarging but pushing through a less dense environment.
The second theory to explain small arrows is that jets are young and have not yet extended to large distances.
The old ones are red the kids are blue
Radio galaxies, both young and old, can characterize by the clever use of modern wireless astronomy: seeing their “radio color”. We looked at data from the Galactic and Extragalactic All Sky MWA (JLIM) survey, which showed the sky 20 different radio frequencies, showing astronomers an incomparable “radio color” of the sky.
From the data, baby radio galaxies appear in blue, meaning they are brighter at higher radio frequencies. Meanwhile old and dead radio galaxies appear red and glow at lower radio frequencies. We detected 554 baby radio galaxies. When we looked at the identical data a year later, we were surprised to see 123 of them shine brightly. It has puzzled us.
Multiple light years in shape cannot change so much in brightness in less than a year without breaking the laws of physics. Therefore, either our galaxies were much smaller than expected, or something else was happening. Fortunately, we had the necessary data for the search.
Past research on the variability of radio galaxies has used a small number of galaxies; archived data collected from many different telescopes or conducted using only a single frequency. For our research, we surveyed more than 21,000 galaxies over a single year across multiple radio frequencies. This makes it the first “spectral variability” study, enabling us to see how galaxies change brightness at different frequencies.
Our Bouncing Baby Radio galaxies have changed so much over the years that we suspect they are children at all. These compact radio galaxies are actually more likely than Angie teens to grow faster than adults are. Although most of our variable galaxies have increased or decreased in brightness by almost the same amount across the color of all radios, some have not.
