Milky Way Center is a Massive Rotating Bar of Stars
In recent decades astronomers have suspected that the center of our galaxy has an elongated stellar structure, or bar, that is hidden by dust and gas. Many spiral galaxies in the universe exhibit such a bar through the center bulge, while other spiral galaxies are simple spirals. Astronomers ask, why? In a recent paper Dr. Andrea Kunder, of Cerro Tololo Inter-American Observatory (CTIO) in northern Chile, and a team of colleagues have presented data that demonstrates how this bar is rotating.
As part of a larger study dubbed BRAVA, for Bulge Radial Velocity Assay, a team assembled by Dr. R. Michael Rich at UCLA, measured the velocity of a large sample of old, red stars towards the galactic center by observing the spectra of these stars, called M giants, which allows the velocity of the star along our line of sight to be determined.
Over a period of 4 years almost 10,000 spectra were acquired with the CTIO Blanco 4-meter telescope, located in the Chilean Atacama desert, resulting in the largest homogeneous sample of radial velocities with which to study the core of the Milky Way.
Analyzing the stellar motions confirmed that the bulge in the center of our galaxy appears to consist of a massive bar, with one end pointed almost in the direction of the sun, which is rotating like a solid object. Although our galaxy rotates much like a pinwheel, with the stars in the arms of the galaxy orbiting the center, the BRAVA study found that the rotation of the inner bar is cylindrical, like a toilet roll holder. This result is a large step forward in explaining the formation of the complicated central region of the Milky Way.
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The full set of 10,000 spectra were compared with a computer simulation of how the bar formed from a pre-existing disk of stars. Dr. Juntai Shen of the Shanghai Observatory developed the model. The data fits the model extremely well, and suggests that before our bar existed, there was a massive disk of stars.
This is in contrast to the standard picture in which our galaxy’s central region formed from the chaotic merger of gas clouds, very early in the history of the Universe. The implication is that gas played a role, but appears to have largely organized into a massive rotating disk, that then turned into a bar due to the gravitational interactions of the stars.
The stellar spectra also allow the team to analyze the chemical composition of the stars. While all stars are composed primarily of hydrogen, with some helium, it is the trace of all the other elements in the periodic table, called “metals” by astronomers, that allow us to say something about the conditions under which the star formed.
The BRAVA team found that stars closest to the plane of the Galaxy have a lower ratio of metals than stars further from the plane. While this trend confirms standard views, the BRAVA data cover a significant area of the bulge that can be chemically fingerprinted. By mapping how the metal content of stars varies throughout the Milky Way, star formation and evolution is deciphered, just as mapping carbon dioxide concentrations in different layers of Antarctic ice reveal ancient weather patterns.
The international team of astronomy on this project has made all of their data available to other astronomers so that additional analysis will be possible. They note that in the future it will be possible to measure more precise motions of these stars so that they can determine the true motion in space, not just the motion along our line of sight.
Over a period of 4 years almost 10,000 spectra were acquired with the CTIO Blanco 4-meter telescope, located in the Chilean Atacama desert, resulting in the largest homogeneous sample of radial velocities with which to study the core of the Milky Way.
Analyzing the stellar motions confirmed that the bulge in the center of our galaxy appears to consist of a massive bar, with one end pointed almost in the direction of the sun, which is rotating like a solid object. Although our galaxy rotates much like a pinwheel, with the stars in the arms of the galaxy orbiting the center, the BRAVA study found that the rotation of the inner bar is cylindrical, like a toilet roll holder. This result is a large step forward in explaining the formation of the complicated central region of the Milky Way.
.
The full set of 10,000 spectra were compared with a computer simulation of how the bar formed from a pre-existing disk of stars. Dr. Juntai Shen of the Shanghai Observatory developed the model. The data fits the model extremely well, and suggests that before our bar existed, there was a massive disk of stars.
This is in contrast to the standard picture in which our galaxy’s central region formed from the chaotic merger of gas clouds, very early in the history of the Universe. The implication is that gas played a role, but appears to have largely organized into a massive rotating disk, that then turned into a bar due to the gravitational interactions of the stars.
The stellar spectra also allow the team to analyze the chemical composition of the stars. While all stars are composed primarily of hydrogen, with some helium, it is the trace of all the other elements in the periodic table, called “metals” by astronomers, that allow us to say something about the conditions under which the star formed.
The BRAVA team found that stars closest to the plane of the Galaxy have a lower ratio of metals than stars further from the plane. While this trend confirms standard views, the BRAVA data cover a significant area of the bulge that can be chemically fingerprinted. By mapping how the metal content of stars varies throughout the Milky Way, star formation and evolution is deciphered, just as mapping carbon dioxide concentrations in different layers of Antarctic ice reveal ancient weather patterns.
The international team of astronomy on this project has made all of their data available to other astronomers so that additional analysis will be possible. They note that in the future it will be possible to measure more precise motions of these stars so that they can determine the true motion in space, not just the motion along our line of sight.
The Daily Galaxy via National Optical Astronomy Observatory
Image credit: ESO
Comments
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Quote:"Many spiral galaxies in the universe exhibit such a bar through the centre bulge, while other spiral galaxies are simple spirals. Astronomers ask, why?"
AD: The answers are very simple: We are talking of cyclical inwards and outwards circuit movements. The barred galaxies have an outgoing movement and the "smooth and close arms" spiralling galaxies with a great luminous centre have an inwards turning movement.
That is: The formation in our galaxy goes outwards from the centre via the bars in a horizontal circular motion that creates both the own-rotation of the stars and planets etc. and the orbiting motion of planets around a star.
This horizontal outgoing movement via the bars also explain the 60 degree difference between the galactic plane and the orbiting plane in our Solar System.
That is again: The Solar system was once formatted directly from within the Milky Way centre and fairly gently slung out in the galactic surroundings, already having the rotation and orbiting velocity and the formation data as we can observe today.
And: This formation explanation also debunks the orthodox explanation of our solar system supposedly being formattet via a local molecular dust cloud that suddenly decided to collapse via gravity. Our solar system is clearly an integrated part of the Milky Way outgoing formation and orbiting motion.
- This outgoing movement in our galaxy explains logically "the galactic rotation anomaly" where objects in our galaxy doesn´t follow the Newtonian laws of celestial orbits around a gravity centre, but orbits in our galaxy with the very same velocity. Newton´s laws clearly doesn´t work here.
The objects in our galaxy have all left the Milky Way centre with the same Milky Way rotation momentum – and therefore all objects orbit the Milky Way centre with the same velocity. There is obviously NO gravitational “black hole” or “black object” in the Milky Way centre – or in other barred galaxies. And there is NO need for “dark matter” in our galaxy to explain the actual orbiting movement.
The only urgent cosmologically need is, in order to understand the movement in the Universe, to look at all formations in the Universe as being cyclically. Something like the movement in a 3D Cell structure with all its dynamic movements via the basically forces of electrodynamics: thermodynamics; hydrodynamics; magnetodynamics and nuclear dynamics.
NB: This galactic formation and motion is also explained very clearly in the many globally and mythically Stories of Creation. One just have to read and interpret the creation myths and symbols as having a concrete cosmological meaning.
Ivar Nielsen
Natural Philosopher
Posted by: Ivar Nielsen | December 20, 2011 at 01:59 AM
Wait... seriously? It's the Milky Way Bar?
That's straight from the Department of You Can't Make This Stuff Up.
(I like it.)
PS: Nice analysis, Ivar.
Posted by: Bob Greenwade | December 20, 2011 at 09:08 AM
I believe our universe is the basic construct showing how an (DNA)amino acid is created in space , but on a grand scale, the body within a body within a body!
Posted by: node | December 21, 2011 at 04:58 AM