The center of our galaxy could be much more powerful than we thought, scientists say

The center of our galaxy could be much more powerful than we thought, scientists say

The center of our galaxy could be much more powerful than we thought, scientists say

There are few sights more beautiful than the orange-red disc of our star, the Sun, sinking into the ocean. As the sun sets, it seems a far cry from the powerful, hot star we feel at noon and cannot even safely gaze at. If we could only see the Sun at sunset, what would we think? It would be fair to conclude that he was much weaker than he actually is.

The same could be true for astronomers’ observations of the centers of galaxies, a new study suggests.

Active galactic nuclei are the most powerful stable and compact energy sources in the cosmos. They are powered by supermassive black holes that swallow matter and far outweigh the combined light of billions of stars in their host galaxies.

Published today in Royal Astronomical Society Monthly NoticesNew research suggests that astronomers may have grossly underestimated the energy output of these objects – and the seemingly fundamental differences between them – simply because their light is dimmed by different amounts of dust.

“When there are small particles in between along our line of sight, it makes things behind them darker,” said Martin Gaskell, lead author and research associate in astronomy and astrophysics at UC Santa Cruz. “We see this at sunset on a clear day when the sun seems weaker.”

The work is based on observations of the active galactic nuclei of NGC 5548, a galaxy 250 million light-years distant in the constellation Bootes that hosts a supermassive black hole.

When the sun is setting, the light reaching the viewer’s eyes has passed through much more of the atmosphere than when it is overhead. Its radiation hits more molecules. Red and orange have the longest wavelengths of light, so they more easily pass through Earth’s atmosphere to reach your eyes. The light intensity is also less, having been filtered by the atmosphere, so you can watch a setting sun with the naked eye. He looks paler.

Similarly, dust in active galactic nuclei also causes them to appear redder than they actually are, with the amount of reddening related to the amount of dimming, the study suggests.

The study shows that “far ultraviolet light from a typical active galactic nucleus is attenuated by a significant factor,” according to Gaskell. It was previously assumed to be negligible.

In the new study of NGC 5548, researchers found that its dimming due to dust is more than ten times greater than the dimming caused by dust when we look at our galaxy, the Milky Way.

The implication is that in ultraviolet light — where most of the energy is radiated — a typical active galactic nucleus emits an order of magnitude more energy than previously thought, Gaskell said. Not only that, but the colors of NGC 5548 are similar to those of other active galactic nuclei, which makes active galactic nuclei in general more powerful than previously imagined.

It also means that the centers of galaxies may, in fact, be much more similar than previously thought, with what were thought to be major fundamental differences between them really just the consequences of different amounts of blushing by dust.

“It makes life easier for researchers and speeds up our understanding of what happens when black holes swallow matter,” Gaskell said.

The article was co-authored by three high school students participating in UCSC’s science internship program – Frances Anderson (now at Harvey Mudd College), Sufia Birmingham (now at Princeton University) and Samhita Ghosh (now at ‘UC Berkeley).

I wish you clear skies and big eyes.

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