Massive Black Holes Dwell In Most Galaxies

Hubble's observation confirmed more than two centuries of theory and conjecture about the reality of black holes. The term black hole was coined in 1967 by American physicist John Wheeler. However, French scientist Simone Pierre LaPlace first speculated that "dark stars" might exist, which would have such intense gravitation that light itself could not escape. Despite this fact (a perfect definition of invisibility), if something is falling into a black hole, it disintegrates completely in the process, radiating high amounts of energy.

A candidate to be a black hole must fullfill these conditions:

It must radiate lots of energy.
This energy must be produced in a relatively small region.
Everything around this object must orbit with high speed.

Some Hubble findings fit all three.

First came the discovery of black holes inside active galaxies. A team of astronomers, leaded by Doug Richstone of the University of Michigan, presented at the 1997 AAS meeting the discovery of three black holes in normal galaxies, suggesting nearly all galaxies may harbor supermassive black holes wich once powered quasars. The key results are:

Supermassive black holes are so common, nearly every large galaxy has one.
A black hole's mass is proportional to the mass of the host galaxy, so that, for example, a galaxy twice as massive as another would have a black hole that is also twice as massive. This discovery suggests that the growth of the black hole is linked to the formation of the galaxy in which it is located.
The number and masses of the black holes found are consistent with what would have been required to power the quasars.

**ADOPTED MASSIVE BLACK HOLE DETECTIONS**
Galaxy	Comment	Constellation	Type	Distance¹	Luminosity²	Mass³
Milky Way			Sbc	2800	1.9	2 Million
NGC 224 = M31	Andromeda Nebula	Andromeda	Sb	2.3 Million	5.2	30 Million
NGC 221 = M32	Satellite of M31	Andromeda	E2	2.3 Million	0.25	3 Million
NGC 3115		Sextans	SO	27 Million	14.2	2 Million
NGC 4258	Maser Detection	Canes Venacti	Sbc	24 Million	1.3	40 Million
NGC 4261		Virgo	E2	90 Million	33	400 Million
NGC 4486 = M87		Virgo	E0	50 Million	56	3 Billion
NGC 4594 = M104	The Sombrero	Virgo	Sa	30 Million	47	1 Billion
New Objects Reported Today
NGC 3377		Leo	E5	32 Million	5.2	100 Million
NGC 3379		Leo	E1	32 Million	13	50 Million
NGC 4486b	Satellite of M87	Virgo	E0	50 Million	0.82	500 Million

Table Footnotes: ¹In units of Light Years; ²In units of one billion solar luminosities. For spirals, we quote bulge luminosities.; ³In units of one solar mass.

These three normal galaxies are believed to contain central supermassive black holes. NGC4486B (lower-left) has a double nucleus (blow-up of the central 0.5 arcseconds on lower-right). The images of NGC 3377 and NGC 4486B are 2.7" on a side and for NGC3379 the size is 5.4".

Massive Black Holes Dwell In Most Galaxies.
Karl Gebhardt (Univ. of Michigan), Tod Lauer (NOAO), and NASA
January 13, 1997

NGC 4261

This is a Hubble Space Telescope image of an 800-light-year-wide spiral-shaped disk of dust fueling a massive black hole in the center of galaxy, NGC 4261, located 100 million light-years away in the direction of the constellation Virgo. By measuring the speed of gas swirling around the black hole, astronomers calculate that the object at the center of the disk is 1.2 billion times the mass of our Sun, yet concentrated into a region of space not much larger than our solar system.

Suprisingly, the black hole is offset by 20 light-yeats from the center of the disc. furthermore, it's not at the exact center of the galaxy. One possibility is that material spilling onto the black hole creates a rocket-like effect.

DUST DISK AROUND A BLACK HOLE IN GALAXY NGC 4261
(L. Ferrarese. 4-12-1995)

M 87
Is located 50 million light-years from us in the Virgo constellation. As early as 1917, astronomers discovered a long finger of energy emanating from the nucleus. Investigations using radio telescopes in the 1950s detected large emissions of energy from the galaxy. In high resolution images, the jet appears as a string of knots (some as small as ten light-years across) within a widening cone extending out from M87's core. A massive black hole had been the suspected "engine" for generating the enormous energies that power the jet. The gravitational energy is released by gas falling into the black hole, producing a beam or jet of electrons spiraling outward at nearly the speed of light.
Hubble's observation confirms more than two centuries of theory and conjecture about the reality of black holes.
"If it isn't a black hole, then I don't know what it is," says Dr. Holland Ford of the Space Telescope Science Institute and The Johns Hopkins University in Baltimore, Maryland.
He used HST's Faint Object Spectrograph to measure the speeds of orbiting gas on regions located about 60 light-years from the black hole at the center. They calculated that the disk of hot (about 10,000 Kelvin), ionized gas is rotating at a speed of about 1.2 million miles per hour (550 kilometers per second).

HUBBLE CONFIRMS EXISTENCE OF MASSIVE BLACK HOLE AT HEART OF ACTIVE GALAXY
(Holland Ford and Richard Harms. 25-5-1994)

NGC 1068
NGC1068 is located at a distance of approximately 60 Million Light Years and is the prototype of a class of galaxies, known as Seyfert Type 2. In active galaxies, typically the core shines with the brightness of a billion solar luminosities, and the brightness of the core fluctuates over the period of a few days implying that the energy is being released from a region only a few light-days in extent. The most likely source for this enormous amount of energy is a "super massive" black-hole with a total mass of 100 million stars like the Sun.

HST REVEALS THE CENTRAL REGION OF AN ACTIVE GALAXY
(D. Macchetto)