Who discovered Seyfert galaxies, and when?

Edwin Hubble in 1929, during his study of galaxy types Carl Seyfert in 1943, who identified a class of spiral galaxies with unusually bright and compact nuclei Vera Rubin in 1970, while measuring galaxy rotation curves Maarten Schmidt in 1963, the same year he identified the first quasar

What is the difference between a Type 1 and a Type 2 Seyfert galaxy?

Type 1 Seyferts are spiral galaxies; Type 2 Seyferts are elliptical galaxies Type 1 Seyferts show both broad and narrow emission lines; Type 2 Seyferts show only narrow lines because the dusty torus hides the broad-line region Type 1 Seyferts have one jet; Type 2 Seyferts have two jets Type 1 Seyferts are more luminous than quasars; Type 2 Seyferts are less luminous than normal galaxies

How do Seyfert galaxies compare to quasars in luminosity?

Seyfert galaxies are as luminous as quasars but much closer to Earth Seyfert galaxies are much less luminous — they represent the low-luminosity end of the AGN spectrum and are far more common Seyfert galaxies are more luminous than quasars because they have larger accretion disks Seyfert galaxies and quasars have identical luminosities

What type of galaxy are Seyfert galaxies?

Spiral galaxies — Seyfert galaxies are almost always spiral or barred spiral galaxies with active nuclei Elliptical galaxies — the smooth shape makes it easy to see the bright nucleus Irregular galaxies — the chaotic structure is caused by their active nucleus Lenticular galaxies — they have a disk but no spiral arms interfering with the nucleus

What is a blazar?

An AGN whose jet is pointed directly away from Earth, making it particularly faint An AGN whose relativistic jet is pointed almost directly at Earth, making it extremely bright and rapidly variable A type of quasar that emits only in the X-ray and gamma-ray bands A galaxy in the process of colliding with another galaxy, causing the nucleus to brighten

What are the two types of blazars?

Megablazars and Microblazars, distinguished by the length of their jets Type 1 and Type 2 blazars, depending on whether the jet is hidden by the dusty torus BL Lacertae objects (BL Lacs) and Flat Spectrum Radio Quasars (FSRQs) Radio blazars and optical blazars, depending on which wavelength they are brightest in

What is NGC 1068 (also known as M77) famous for?

The first quasar ever discovered It is the most studied Type 2 Seyfert galaxy, providing key evidence for the dusty torus hiding the broad-line region A blazar with the most powerful jet ever measured The nearest radio galaxy to the Milky Way

Why are blazars important for high-energy astrophysics?

Blazars are useful because they are close enough to image with optical telescopes Blazars are only important for radio astronomy — they emit no high-energy radiation Blazars are among the most powerful particle accelerators in the universe and are likely sources of high-energy cosmic rays and neutrinos Blazars are important because they are the only AGN that host Cepheid variable stars

How does the unified model explain the different types of AGN?

Each AGN type represents a completely distinct physical object formed by a different mechanism All AGN types have the same basic structure; the apparent differences arise from the viewing angle and the power of the central black hole The different AGN types represent different stages of a black hole's life cycle AGN types are determined by the type of host galaxy — ellipticals always produce one type, spirals another

Why do blazars show dramatic brightness variations on timescales as short as hours?

Blazars orbit close enough to Earth that we can detect individual stellar flares in their nuclei The central black hole in a blazar spins faster than in other AGN, causing rapid changes Changes in the jet emission — such as shocks moving through the jet or new blobs of plasma being ejected — are amplified by relativistic beaming and reach us almost simultaneously Blazars vary because their host galaxies are rapidly rotating and taking the jet in and out of alignment