galactic nucleus

Scientific  

1. The center of a galaxy, usually small, very bright, and containing a high density of stars and other objects.

2. ◆ An active galactic nucleus is a nucleus that emits more radiation than can be explained in terms of stars alone. Blazars and quasars are thought to be active galactic nuclei; the nuclei of Seyfert galaxies are also active, and are thought to contain an extremely massive black hole.

---

Example Sentences

De Graaff and her colleagues tested a wide range of galaxy and active galactic nucleus models against the object's spectrum, attempting to reproduce its features.

From Science Daily

In this model, the central engine is an active galactic nucleus containing a supermassive black hole with an accretion disk, but instead of dust, the entire system is enshrouded in a thick layer of hydrogen gas that reddens the emitted light.

From Science Daily

The active galactic nucleus heats the surrounding gas envelope in a way that resembles how fusion heats the outer layers of a star, producing a similar outward appearance.

From Science Daily

The steep rise in the spectrum that inspired the name The Cliff can be explained by a dense, spherical, turbulent gas envelope around an active galactic nucleus.

From Science Daily

For the first time, researchers believe they have observed a supermassive black hole begin to gorge on surrounding gas, transforming itself into an active galactic nucleus—and in doing so, becoming the brightest steady light source in the universe.

From Science Magazine