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Seyfert galaxy - Wikipedia


Seyfert galaxies are one of the two largest groups of active galaxies, along with quasars. ... In 1943, Carl Keenan Seyfert discovered more galaxies similar to NGC 1068 and ... It has been later not...

Chapter 17 - Astronomy


More recently, astronomers have discovered objects that fit none of Hubble's categories, ... the spiral arms come from the ends of a bar through the nucleus rather than from the nucleus itself. 4. ..... Some irregulars are seen to be pairs of galaxies in collision. ... An active galaxy is a galaxy with an unusually luminous nucleus...

Active Galaxies - Astronomy Notes


Jun 2, 2007 ... When the universe was younger, some galaxies produced a lot ... A peculiar group of galaxies are extremely luminous but very compact. ... an ``active galaxy'' to be a galaxy with a very luminous nucleus. ... Later, some other blue star-like objects at large redshifts were discovered to have no radio emission ...

Active galactic nuclei - D.E. Osterbrock - NED


Many of the most luminous radio galaxies are morphologically classified as ... In many cases these spectra are earlier in spectral type than normal spirals, ... Only one `Seyfert 2 QSO' has been reported, E 0449-184, originally discovered as .... definition of a very low-luminosity Seyfert 1.8 nucleus with unusually narrow lines .

Hubble sequence - University of Oregon


Some galaxies have spiral or pinwheel arms. .... It has a bright nucleus, an unusually large central bulge, and a prominent dust lane in its ... Most representatives of this class consist of grainy, highly irregular assemblages of luminous areas.

galaxy - Types of galaxies | astronomy | Britannica.com


Apr 13, 2016 ... Some of the features of this revised scheme are subject to argument because of ... do in fact have small numbers of luminous O and B stars as well as dust lanes. ... The normal spirals have arms that emanate from the nucleus, while barred ...... It was discovered that galaxies and galaxy clusters tend to fall in .....

Active Galaxies and Quasars - Introduction and Glossary


Introduction - Discovery of Active Galactic Nuclei ... the set of (mostly spiral) galaxies whose spectra showed unusually broadened emission lines from bright, starlike nuclei. ... Both kinds have very similar sets of emission lines seen, implying the ... Optical telescopes showed a variety of spectra for radio galaxies - some ...

Hubble Looks at Stunning Spiral | NASA


The northern nucleus also hosts a black hole with some 100 million times the mass of ... In 1900, astronomer Joseph Lunt made a discovery: Peering through a ... Because of this, all the stars have the same age and composition, but vary in their .... face-on spiral galaxy NGC 6814, whose luminous nucleus and spectacular ...

Hubble Spies the Barred Spiral Galaxy NGC 4394 | NASA


May 6, 2016 ... NGC 4394 is the archetypal barred spiral galaxy, with bright spiral arms ... of the lowest black hole masses known in any luminous galactic core. ... The northern nucleus also hosts a black hole with some 100 million times the mass of the sun! .... Its unusual combination of features are thought to have been ...

LUMINOUS INFRARED GALAXIES ir >1012 - Institute for Astronomy


KEY WORDS: luminosity function, starbursts, active galactic nuclei, .... spiral galaxies and also singled out several \ultrahigh" infrared luminous. galaxies whose .... Although some previously cataloged objects would prove to have. extreme ... objects quickly led to the discovery of faint galaxies, typically at redshifts. 0.1{0.2...