This week’s image from the Hubble Space Telescope shows galaxy NGC 5728, captured in both the infrared and visible light wavelengths. This is a particularly energetic type of galaxy, called a Seyfert galaxy, with a very bright galactic nucleus.
“In this image, NCG 5728 appears to be an elegant, luminous, barred spiral galaxy,” the Hubble scientists write. “What this image does not show, however, is that NGC 5728 is also a monumentally energetic type of galaxy, known as a Seyfert galaxy. This extremely energetic class of galaxies is powered by their active cores, which are known as active galactic nuclei (AGNs). There are many different types of AGNs, and only some of them power Seyfert galaxies.”
Other types of galaxies with active galactic nuclei, like quasars, are difficult to see because the amount of radiation they emit obscures the entire galaxy. But Seyfert galaxies like NGC 5728 can be seen clearly and look much like standard galaxies.
This image was captured using Hubble’s Wide Field Camera 3, which images in both the visible light and infrared wavelengths, allowing it to capture the galaxy in all its glory. However, there is even more light being given off by the AGN in other wavelengths which can’t be captured by Hubble’s instruments.
This is one reason why astronomers observe the universe in a variety of wavelengths, like ultraviolet light, X-rays, or radio wavelengths. Each different wavelength allows them to see different features in nature. The infrared wavelength used by Hubble, for example, is particularly good for looking through clouds of dust to see structures that would otherwise be obscured.