Its challenging to make high-resolution images of such a big object in the sky, which is why a current study of Centaurus A is so impressive.
One concept thats difficult to visualize is the obvious size of objects in the sky. No the actual size of a things, however rather the quantity of area a things covers in the sky. Obvious size depends on an items real size and its range from us. The Sun is about 400 times wider than the Moon, but also about 400 times more remote, so the Sun and Moon have approximately the same evident size.
One idea thats hard to picture is the evident size of items in the sky. No the real size of an item, however rather the quantity of area a things covers in the sky. Apparent size depends upon an objects real size and its range from us. The Sun is about 400 times larger than the Moon, however likewise about 400 times more remote, so the Sun and Moon have roughly the exact same apparent size.
A composite image comparing the size of the Moon with the Andromeda galaxy. Credit: Tom Buckley-Houston/Stephen Rahn/NASA
The majority of the astronomical images we see are of single objects. So when we see a photo of a galaxy, we might believe it needs to be truly small, and the telescope just made it appear big. That isnt always the case. Take, for instance, the Andromeda galaxy. With the naked eye, we can just see it as a small faint spot in the constellation Andromeda. Even then we can only see it under very dark conditions. If it were much better (or our eyes much more light-sensitive) we would see a vast galaxy roughly five times wider than the Moon. It would be a tremendous sight. The very same holds true of numerous nebulae. The Orion nebula appears bigger than the Moon, and some fainter nebulae are even larger.
Of course, these contrasts just consider appearances in noticeable light. The sky would appear extremely different if you include other wavelengths such as radio. Huge radio light is produced in a number of ways, but one of the most common sources are the jets powered by galactic black holes. Ionized plasma is spewed away from the stellar core, producing substantial lobes that produce radio light. By studying these radio lobes, astronomers can better understand supermassive great voids.
A radio picture of Centaurus A. Credit: Ben McKinley, ICRAR/Curtin and Connor Matherne
One of the closest and most powerful active galaxies is Centaurus A. Its about 12 million light-years from Earth. However its jets are so large that they cover more than 16 Moon-widths in the sky. Hold your hand at arms length, splay your fingers, whichs how large Centaurus A would appear if you could see in radio
Its tough to make high-resolution images of such a big things in the sky, which is why a recent study of Centaurus A is so outstanding. Utilizing the Murchison Widefield Array (MWA) in Western Australia, the group mapped the radio lobes in information. They then combined it with optical and x-ray data. The team did more than create a fantastic image. From their data, they found evidence to support an idea understood as disorderly cold accretion. Essentially, that cold gas within the stellar halo can be up to the black hole, which in turn powers the development of large jets. This might help describe why some galaxies such as Centaurus A have tremendously active great voids.
It all goes to show what astronomers can learn when they take a broader view.
Recommendation: McKinley, B., et al. “Multi-scale feedback and feeding in the closest radio galaxy Centaurus A.” Nature Astronomy (2021 ): 1-12.
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