Sigma (cosmology)
Encyclopedia
Sigma in cosmology
was a property of galaxies
used when trying to work out the mystery of galaxies and their supermassive black hole
s.
experts had made observations with a spectroscope of two galaxies, one of an active galaxy
with an active galactic nucleus called NGC10-68 and a dormant galaxy next door to us named Andromeda
.
The observations are shown. The light from the centre in Andromeda galaxy was distorted proving the existence of super-massive black holes.
Other observations proved most galaxies had a similar centre whether it be active or dormant.
They then realised that the black hole
s must have something to do with a galaxy's formation, so they turned to something they thought was useless: the speed of the star
s around the edge of the galaxy. This was Sigma, the speed of the stars at the edge of the galaxy supposedly unaffected by the mass of the black hole at the centre.
team calculated the sigma of several stars in different galaxies and the mass of the black hole at the (nucleus) centre. They expected no correlation
what so ever. But when plotting their results on a Scatter diagram and drawing a line of best fit they ended up with a positive correlation. It appeared that the heavier the black hole
at the centre was the faster the stars within the galaxy travelled.
This property helped them realise that a Supermassive black hole
nucleus must be the reason for the galaxies in some way.
They saw that the clouds of gas before the galaxies compressed forming a black hole, the black hole would produce phenomenal amounts of energy which would force the rest of the galaxy away and form stars.
Sigma comes into use when the black hole gets heavier from the increased mass
. The stars at the edge of the newly formed galaxy were spinning around at high speeds. The faster they were travelling, the heavier the black hole would have to be to force them away. Then once everything had been moved away from it the black hole stops feeding.
The correlation above has been proved by the process of galactic creation. (see Galaxies)
in lower case with star velocity in subscript (σν☉). In physics and mathematics lower case sigma means set or group. This is appropriate for the property sigma as it is a measurement of a group of star speeds.
The above correlation is given by-
[(Q2+(J/M)2≤M2)=106*M☉]≈50 km/s(σν☉)
The black hole mass equal to 1,000,000 times the mass of the sun is approximately equal to the sigma of a star travelling at 50 km/s.
The increase factor is
106n*101=xKm/s+50 km/s.
Cosmology
Cosmology is the discipline that deals with the nature of the Universe as a whole. Cosmologists seek to understand the origin, evolution, structure, and ultimate fate of the Universe at large, as well as the natural laws that keep it in order...
was a property of galaxies
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
used when trying to work out the mystery of galaxies and their supermassive black hole
Supermassive black hole
A supermassive black hole is the largest type of black hole in a galaxy, in the order of hundreds of thousands to billions of solar masses. Most, and possibly all galaxies, including the Milky Way, are believed to contain supermassive black holes at their centers.Supermassive black holes have...
s.
History
In the late 1990s the NUKERNuker Team
The Nuker Team was organized in 1985 to use the Hubble Space Telescope, with its high-resolution imaging and spectroscopy, to investigate the central structure and dynamics of galaxies. The team uses the space telescope to examine supermassive black holes and determined the relationship between a...
experts had made observations with a spectroscope of two galaxies, one of an active galaxy
Active galactic nucleus
An active galactic nucleus is a compact region at the centre of a galaxy that has a much higher than normal luminosity over at least some portion, and possibly all, of the electromagnetic spectrum. Such excess emission has been observed in the radio, infrared, optical, ultra-violet, X-ray and...
with an active galactic nucleus called NGC10-68 and a dormant galaxy next door to us named Andromeda
Andromeda Galaxy
The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the...
.
The observations are shown. The light from the centre in Andromeda galaxy was distorted proving the existence of super-massive black holes.
Other observations proved most galaxies had a similar centre whether it be active or dormant.
They then realised that the black hole
Black hole
A black hole is a region of spacetime from which nothing, not even light, can escape. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that...
s must have something to do with a galaxy's formation, so they turned to something they thought was useless: the speed of the star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s around the edge of the galaxy. This was Sigma, the speed of the stars at the edge of the galaxy supposedly unaffected by the mass of the black hole at the centre.
Usage In Cosmology
The NUKERNuker Team
The Nuker Team was organized in 1985 to use the Hubble Space Telescope, with its high-resolution imaging and spectroscopy, to investigate the central structure and dynamics of galaxies. The team uses the space telescope to examine supermassive black holes and determined the relationship between a...
team calculated the sigma of several stars in different galaxies and the mass of the black hole at the (nucleus) centre. They expected no correlation
Correlation
In statistics, dependence refers to any statistical relationship between two random variables or two sets of data. Correlation refers to any of a broad class of statistical relationships involving dependence....
what so ever. But when plotting their results on a Scatter diagram and drawing a line of best fit they ended up with a positive correlation. It appeared that the heavier the black hole
Black hole
A black hole is a region of spacetime from which nothing, not even light, can escape. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that...
at the centre was the faster the stars within the galaxy travelled.
This property helped them realise that a Supermassive black hole
Supermassive black hole
A supermassive black hole is the largest type of black hole in a galaxy, in the order of hundreds of thousands to billions of solar masses. Most, and possibly all galaxies, including the Milky Way, are believed to contain supermassive black holes at their centers.Supermassive black holes have...
nucleus must be the reason for the galaxies in some way.
They saw that the clouds of gas before the galaxies compressed forming a black hole, the black hole would produce phenomenal amounts of energy which would force the rest of the galaxy away and form stars.
Sigma comes into use when the black hole gets heavier from the increased mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
. The stars at the edge of the newly formed galaxy were spinning around at high speeds. The faster they were travelling, the heavier the black hole would have to be to force them away. Then once everything had been moved away from it the black hole stops feeding.
The correlation above has been proved by the process of galactic creation. (see Galaxies)
Formulation and Notation
Sigma is given by the Greek letter sigmaSigma
Sigma is the eighteenth letter of the Greek alphabet, and carries the 'S' sound. In the system of Greek numerals it has a value of 200. When used at the end of a word, and the word is not all upper case, the final form is used, e.g...
in lower case with star velocity in subscript (σν☉). In physics and mathematics lower case sigma means set or group. This is appropriate for the property sigma as it is a measurement of a group of star speeds.
The above correlation is given by-
[(Q2+(J/M)2≤M2)=106*M☉]≈50 km/s(σν☉)
The black hole mass equal to 1,000,000 times the mass of the sun is approximately equal to the sigma of a star travelling at 50 km/s.
The increase factor is
106n*101=xKm/s+50 km/s.