This image from the Hubble Space Telescope features MCG-01-24-014. It is a spiral nebula situated 275 million light-years away with an active galactic nucleus, categorizing it as a Type-2 Seyfert galaxy. Seyfert galaxies, typically nearer to Earth compared to quasars, are identified by their special spectra, especially the prohibited emissions in Type-2 Seyferts. Credit: ESA/Hubble & & NASA, C. KilpatrickThis whirling Hubble Space Telescope image includes a bright spiral nebula understood as MCG-01-24-014, which lies about 275 million light-years from Earth. In addition to being a well-defined spiral galaxy, MCG-01-24-014 has an extremely energetic core, understood as an active galactic nucleus (AGN), so it is described as an active galaxy.Even more particularly, it is categorized as a Type-2 Seyfert galaxy. Seyfert galaxies host one of the most common subclasses of AGN, along with quasars. Whilst the accurate classification of AGNs is nuanced, Seyfert galaxies tend to be relatively nearby ones where the host galaxy remains plainly noticeable alongside its main AGN, while quasars are invariably extremely remote AGNs whose extraordinary luminosities outshine their host galaxies.Understanding Seyfert Galaxies and Their SpectraThere are further subclasses of both Seyfert galaxies and quasars. In the case of Seyfert galaxies, the predominant subcategories are Type-1 and Type-2. These are separated from one another by their spectra– the pattern that results when light is split into its constituent wavelengths– where the spectral lines that Type-2 Seyfert galaxies discharge are especially related to specific so-called prohibited emission.To understand why produced light from a galaxy could be considered prohibited, it assists to comprehend why spectra exist in the very first place. Spectra look the method they do due to the fact that specific atoms and molecules will take in and produce light very dependably at really particular wavelengths.The factor for this is quantum physics: electrons (the tiny particles that orbit the nuclei of atoms and particles) can just exist at extremely specific energies, and for that reason electrons can just lose or acquire really specific quantities of energy. These extremely specific quantities of energy represent specific light wavelengths being taken in or emitted.The Phenomenon of Forbidden EmissionsForbidden emission lines, therefore, are spectral emission lines that ought to not exist according to certain rules of quantum physics. But quantum physics is complicated, and some of the rules utilized to anticipate it use presumptions that suit laboratory conditions here on Earth.Under those guidelines, this emission is prohibited– so unlikely that its ignored. In area, in the midst of an exceptionally energetic galactic core, those assumptions do not hold any longer, and the prohibited light gets an opportunity to shine out towards us.
