Astronomers discover hundreds of new galaxies by ignoring the avoidance zone

There are regions of the sky that astronomers are afraid to see. Filled with a cloud of black dust, hiding an invisible mass. It has a very large mass and attracts the Milky Way and other galaxies.

Well, that may be an exaggeration, but it’s true. This region is known as the avoidance zone, and it happens to lie roughly in the direction of the galactic center. Our view of the universe is not as perfect as we would like it to be. The Sun is located within the galactic plane of the Milky Way, approximately 30,000 light-years from its center. If you look north or south of the galactic plane, you get a very ordinary view of the universe. We can peer deep into the sky and see distant galaxies.

But if you look toward the center of the galaxy, you won’t get a clear view. Instead, we see lots of stars, gas, and dust. This is fine if you want to study stars, gas, and dust, but it means that the view of distant space becomes less visible in that direction. If you want an unbiased view of the universe, you avoid that area, hence the term.

It is true that we are being pulled in that direction. There happens to be a supercluster of galaxies called the Great Attractor. We can map it out a bit by studying the relative motion of nearby galaxies. We can also see X-rays from the supercluster, so we know it’s there. However, the avoidance zone is full of gas and dust, so it cannot be studied optically. One thing we know so far is that the Great Attractor is actually made up of multiple clusters. The closest one is known as the Norma cluster, while the larger and more distant one is called the Bela supercluster. That said, there’s still a lot we don’t know about this region.

Fortunately, radio light can penetrate the dust in the zone, so radio astronomers tried to map the area. One drawback is that radio telescopes often don’t have a wide field of view, making it difficult to map the area. But new work is progressing. The paper will be published on the arXiv preprint server.

The new study uses data from the MeerKAT array telescope in South Africa. MeerKAT is particularly sensitive to neutral hydrogen radio radiation known as the HI or (21 centimeter) line. Hydrogen is abundant in the universe, so the distribution of hydrogen can be used to determine the distribution of galaxies and star clusters.

In this study, we mapped the region of the zone in the direction of the Vera supercluster with sufficient resolution to distinguish individual pockets of neutral hydrogen surrounding the galaxy. In this way, the research team was able to discover 719 galaxies within the Vera cluster. Less than a third of them were previously known.

This is just MeerKAT’s first detailed survey of the Bella Supercluster, demonstrating the true power of this relatively new observatory. Future research should provide a deeper understanding of the zones that astronomers tend to avoid.