FORMATION

If a star is large enough and it collapsed, it is possible that nothing (including light) could escape from it. All the matter of a star (even its energy) would be drawn into a dense single point.

SCHARZSCHILD BLACK HOLES

If the core of a star collapses and contains more than 2-3 solar masses, it will continue to shrink down into a singularity and form a black hole. If the object becomes small enough, the escape velocity nearby is so high that no light can escape. Information about the object or about the volume of space near it can not be recieved after it reaches this point. This region is refered to as a black hole. The boundary around this region in called the event horizon, because any event that takes place inside the surface is invisible to an outside observer. The Schwarzschild radius (Rs) is the radius within which an object must shink to become a black hole. Schwarzschild radius=2GM/c^2, where G is the gravitational constant (6.67X 10^-11 Nm^2/kg^2), M is the mass, and c is the speed of light.

KERR BLACK HOLES

A solution to the equations of general relatitivy that describes the properties of a rotating black hole. The rotation of a Kerr black holes splits the event horizon into two concentric surfaces, which touch at the poles. The region between these surfaces is known as the ergosphere. In the ergosphere, one could not resist being dragged around the black hole. It is possible for a particle to escape from the ergosphere and extract energy from the black holes.

Name of star	Black hole mass (in solar masses)	Scharzschild Radius (distant to event horizon)
A0620-00	3-4	8844-11792 m
Cygnus X-1	4-8	11792-23585m
Sco X-1	3-10	8844-23585m
GS2000+25	3-10	8844-23585m
GX339-4	3-10	8844-23585m
V 404 Cygni	8-12	23585-35377m
Nova Muscae 1991	3-10	8844-23585m
Nova Ophiuchi 1977	6-7	17688-20636m
LMC X-3	7-10	20636-23585m

Galaxy Name	Black hole mass (in solar masses)	Scharzschild Radius (distant to event horizon)
IE1740.9-2942	100,000	0.0019 Au
SgrA	2,000,000	0.0396 Au
Messier 32	3,000,000	0.0594 Au
Centaurus A	< 14,000,000	< 0.2770 Au
Messier 31	30,000,000	5.9358 Au
Messier 106	40,000,000	0.7914 Au
NGC 3379	50,000,000	0.9893 Au
NGC 3377	100,000,000	1.9786 Au
Messier 84	300,000,000	5.9358 Au
NGC 4486B	500,000,000	9.8931 Au
NGC 4594	1 X 10^9	19.7861 Au
NGC 4261	1 X 10^9	19.7861 Au
NGC 3115	2 X 10^9	39.5723 Au
Messier 87	3 X 10^9	59.3585 Au
Cygnus- A	5 X 10^9	98.9309 Au
Messier 51	Unknown
NGC 4151	Unknown

Galaxy	RA	Dec	Location	Type	Distance	M B	M BH
(units-->)	h m s	deg min sec	Constellation		light-years		M Sun
OurGalaxy	17 45 40	-29 00 28	Sag	Sbc	2.8X10^3	-17.7	3X10^6
M32= NGC221	0 42 41.9	+40 51 55	Andro	E2	2.3X10^6	-15.5	3X10^6
M31= NGC224	0 42 44.4	+41 16 8	Andro	Sb	2.3X10^6	-18.8	3X10^7
NGC3115	10 5 14.1	-7 43 7	Sextans	S0	27X10^6	-19.9	1X10^9
M104= NGC4594	12 39 59.4	-11 37 22	Virgo	Sa	30X10^6	-20.9	1X10^9
NGC3377	10 47 41.7	+13.59 0	Leo	E5	32X10^6	-18.8	8X10^7
M105= NGC3379	10 47 49.9	+12 34 57	Leo	E1	32X10^6	-19.8	1X10^8
NGC4342	12 23 38.8	+7 3 19	Virgo	S0	50X10^6	-17.0	3X10^8
NGC4486B	12 30 32.1	+12 29 27	Virgo	E1	50X10^6	-16.7	6X10^8
M84= NGC4274	12 25 3.7	+12 53 15	Virgo	E1	50x10^6	-21.0	1X10^9
M87= NGC4486	12 30 49.7	+12 23 24	Virgo	E0	50X10^6	-21.4	3X10^9
NGC4261	12 19 22.8	+5 49 36	Virgo	E2	94X10^6	-20.9	5X10^8
NGC7052	21 18 33.1	+26 26 55	Vulpecula	E4	191X10^6	-21.3	3X10^8
NGC6251	16 32 33.6	+82 32 17	Ursa Minor	E2	346X10^6	-22.7	6X10^8
M77= NGC1068	2 42 40.2	-00 00 48	Cetus	Sb	49X10^6	-18.8	1X10^7
M106= NGC4258	12 18 57.9	+47 18 16	Canes Venatici	Sbc	24X10^6	-17.3	4X10^7
NGC4945	13 05 26.2	-49 28 15	Centaurus	Scd	12X10^6	-15.1	1X10^6
ARP220			Serpens		250X10^6
M51= NGC5194			Whirlpool Galaxy		23X10^6
NGC1316			Fornax A Galaxy		53X10^6
NGC1566			Dorade		50X10^6
M33= NGC598			Triangulum Galxy		2.7X10^6
NGC5128			Centarius A		10X10^16		1X10^9
GX339-4	17 02 49	-48 47 35

*RA=right ascension in hours, seconds, and minutes*Dec=declination*M B=absolute magnitude*M BH=black hole mass realative to solar mass*

A0620-00 is an X-ray binary companion of a K star. 490-560nm spectra for A0620-00 was obtained at KPNO on January 17, 1985. The mass of the compart X-ray source is found to have a lower limit of 3.2 solar masses, strongly implying that it is a black hole, its mass is shown to exceed 7.3 solar masses if the K dwarf fills its Roche lobe during quiescence.

Cygnus X-1 was discovered as an X-ray source 30 years ago. This binary system is distant of 2.5 kpc, consists of the O9.7 Iab type supergiant with a temperature of about 31,000 K called, HDE 226868. A companion, significantly larger then 5 solar masses. It is about 14,000 light years away form earth. The rotation seen through spectral lines shifts back and forth of about 5.6 days. Of course, there is evidence that says that Cyhnus X-1 is not a black hole. It could be that HDE 226868 has a low mass for its size.

Nova Muscae 1991 is an X-ray binary believed to be composed of a low-mass late-type companion that is orbiting a massive object, possibly a black hole. The nova event was detected in 1991 both as a transient X-ray source and as an increase in optical brightness by about eight magnitudes. The tremendous brightening of the source probably arose from the sudden accretion of material from the low mass star onto its invisible companion. Recent optical photometric and spectroscopic observations reveal an orbital period of 10.4 hours. The low mass KO-K4 star is orbiting around an invisible companion with a maximum observed velocity of 409 km/s. Because the inclination of the orbit to the plane of the sky is unknown, the mass of the compact companion cannot be determined for sure. However, it is quite likely that the invisible star is at least 3 solar masses and therefore might be a black hole.