Could the black hole in the center of the galaxy be a white hole? In the center of the galaxy there is a strong radio source which we call Sagittarius A*. Based on the high speed and orbit of nearby stars we have calculated that something with the mass of more than 4 million Sun’s is located in this small area of space. And such a big mass in such a small area can only be a black hole, and the observed electromagnetic radiation comes from the accretion disk of the black hole.
But there is also another solution to this method of logic deduction, Sagittarius A* might optionally be a white hole.
”Like black holes, white holes have properties like mass, charge, and angular momentum. They attract matter like any other mass, but objects falling towards a white hole would never actually reach the white hole's event horizon” source
And if we look at the observations this solution seems to fit beautifully:


*

*Sagittarius A* don’t have any "appetite". The  Chandra telescope observe a lot of gas close to Sag A*, and this gas is ejected outwards by an unknown mechanism. We have never observed anything going into Sag A*, but based on the light given off by Sag A* the researchers have calculated that less than 1 % is "eaten" by the black hole and more than 99 % is the ejected gas we observe. The gas is not ejected outwards by gravitational slingshot effects, as it is too close and have too little velocity, tidal forces ejecting material is one hypothesis they are working on to explain this mystery. If Sag A* is a black hole it seems like there is some strange physics going on, if Sag A* is a white hole, ejection of material is what we would expect.

*Light is flowing from a much larger area then a tiny accretion disk of a black hole. If energy, matter and antimatter is pouring in through Sag A* this will create light. The Chandra telescope did neither observe the accretion disk which we expected to see with Chandra's high detail and resolution, only gas being ejected from Sag A*.

*A large area around Sag A* is energized. A black hole doesn’t energize nearby space much, but mostly energizes a tiny accretion disk.

*Close to the galactic center we observe the formation of many new stars, it is the most massive breeding ground for new stars in the galaxy and a large area close to the galactic center is populated by young stars. A black hole would devour stars instead of giving birth to stars, while a white hole would give excellent conditions for star birth. Neither have we observed any star being devoured by Sag A*, or anything else, and we have observed it for 40 years.

*In 2011 the scientists got exited, a huge cloud of gas called G2 was accelerating towards Sagittarius A*, they expected that the black hole to pull apart and devour the gas cloud and the accretion disk of the black hole would light up. But it was a big flop as the accretion disk showed no sign of lighting up and nothing extra was eaten, and it is a mystery that G2 was not ripped apart by the strong gravitational forces of the black hole. Now they speculate if G2 actually is a star. Well if it is a star, and it is not feeding the black hole, could it instead feed itself?

*We observe a large cloud of antimatter in the galactic center, where
the highest intensity of the signature frequency is at Sag A*. 

There is a theory that wormholes shift matter into antimatter.
Antimatter is often described as matter with reversed time, also
discussed in this
question.
A wormhole would cause matter to go back in time and it might then
shift into antimatter:

...wormhole would seem to allow the conversion of matter to antimatter Source
  Wikipedia

If Sagittarius A* is a white hole it could then be the source of the
antimatter we observe. Today the antimatter is explained by being
created by some binary x-ray stars close to the galactic centre, but
why do we then only see this behavior for these binary stars and not
all the millions of others? They neither know how these stars
potentially produce the antimatter or why the amount is so high.

*The universe is expanding with an accelerated speed. This requires energy to be added, and if energy pours in through white holes, energy is added.

*Black hole singularity physics has not been able to come to final answers despite huge effort, still many says that the laws of physics break down inside a black hole and we can't find the final solutions. We have never observed any singularity elsewhere in the universe or in micro scale. So why are so many sure that a black hole singularities exist?

*Information seems to be lost in a black hole singularity, which goes against the rules of quantum mechanics; a white hole would be a solution to this black hole information paradox.

*Two gigantic fermi bubbles extends up and down from the galactic center, for at least 30 000 light years. These bubbles requires wast amounts of energy to be created and can't be created by a slumbering black hole accretion disk. So the scientist suggests that the black hole had an eruption 2 million years ago. Instead of erupting black holes, a white hole could fuel the fermi bubbles.


*Quasars are active galactic nuclei that can be 100 times brighter than the whole Milky Way. Quasar are currently believed to be made from the accretion disk of black holes, and they shoot out immense galactic jets, but the exact physics is unclear. Quasars show strange redshifts which by using Hubbles law put them up to 29 billion light years comoving distance away, this is larger and longer than the universe, which is explained by the expansion of the universe. These observations puts many of the most powerful quasars in the early universe. Astronomer Halton Arp pointed out that often quasars don't match the redshift of its surroundings and might be much closer than what redshift show, he worked with it for many years and found quite a lot of evidence, but he was ridiculed as science trust distance measured by redshift. There is one solution that allows both Arp and science to be correct, that quasars are white holes connected to a wormhole, and we might be staring into another universe or optionally, another part of this universe. Another fun fact, before accretion disk theory took over and explained quasars, there was this hypothesis that quasars where the white end of a wormhole.

*The stars around Sgr A* is young and close to their escape velocity, and then had to migrate from the galactic disk and break down to come into an orbit, If Sag A* is a white hole they could be made where they are, and be pushed outward which makes them go close to their escape velocity.:



The researchers hope to continue to study the dancing stars to solve a long-held riddle as to how such stars ended up in their orbits about Sagittarius A*. They are too young to have migrated far, and scientists think it's improbable the stars formed in their current orbits where they'd be exposed to the extreme tidal forces of the black hole.
  http://www.space.com/6208-observations-detail-milky-big-black-hole.html



*The Penrose Schwarzschild-radius space time diagram, compress space and time so it can be drawn on a sheet of paper, it includes a black hole and a white hole. They are kind of embarrassed of the white hole, as no one has seen it, and if there were any white holes they would certainly light up so we could observe them. A white hole would stand out while a supermassive black hole could more easily hide in the shadows. 
If we just look at these observations it might seem like they count in favor of Sag A* being a white hole. And it is an important question, as science are currently stuck with the option that Sag A* is a black hole singularity. If there is a white hole in the center of the galaxy instead, the implications are enormous and it could give us answers to many grand problems in astrophysics.

A white hole or a black hole? That's the question!
 A: 
Could the black hole in the center of the galaxy be a white hole?

I think not. IMHO there are no white holes. IMHO white holes are a mathematical fantasy. 

In the center of the galaxy there is a strong radio source which we call Sagittarius A*. Based on the high speed and orbit of nearby stars we have calculated that something with the mass of more than 4 million Suns is located in this small area of space. And such a big mass in such a small area can only be a black hole, and the observed electromagnetic radiation comes from the accretion disk of the black hole.

That's what people say. We're pretty confident that there's something very massive and very small there, but we aren't so confident that the radiation comes from an accretion disk.  

But there is also another solution to this method of logic deduction, Sagittarius A* might optionally be a white hole. ”Like black holes, white holes have properties like mass, charge, and angular momentum. They attract matter like any other mass, but objects falling towards a white hole would never actually reach the white hole's event horizon” source

Note that the article says there are no known processes through which a white hole could be formed. And that we don't actually know that a black hole has the properties of charge and angular momentum. And that according to the "frozen star" black hole interpretation, objects falling towards a black hole never cross the event horizon. See mathspages for a mention of that. It's not a particularly favourable mention, but hey ho.   

And if we look at the observations this solution seems to fit beautifully:
  1.Sagittarius A* don’t have any "appetite"...

Rather surprisingly, people say that only a small percentage of infalling matter makes it into the black hole. An awful lot of it gets "blown away". See this physicsworld article where you can read that "according to new research done in the US that suggests that the black hole – called Sagittarius A* – has a tendency to blow away 99.99% of the matter available for its consumption". 

So the Sag A* rather pushes material away than devours it.

Yes. And in 2001 Friedwardt Winterberg proposed a form of a "firewall" wherein a black hole devours no material at all, because it breaks material down into photons and neutrinos and creates a gamma-ray-burst.  

If energy, matter and antimatter is pouring in through Sag A* this will create light.

There's other ways this can happen. Which do not involve matter falling up. That's the showstopper I'm afraid. There are stars in tight orbits, because of an intense gravitational field.   


A large area around Sag A* is energized. A black hole doesn’t energize nearby space much, but mostly energizes a tiny accretion disk.

Remember we don't actually know what a black hole is really like.  

A black hole would devour stars instead of giving birth to stars

People have suggested that black holes give birth to whole galaxies. See this for example: "A startling new study suggests that supermassive black holes can trigger the formation of stars, thus 'building' their own host galaxies". 

We observe a large cloud of antimatter in the galactic center

See Wikipedia where you can read that the cloud is asymmetrical and matches the pattern of X-ray binaries. It might not be anything to do with black holes.  

the antimatter is explained by being created by some binary x-ray stars close to the galactic centre, but why do we then only see this behavior for these binary stars and not all the millions of others? 

Ah, I see you've spotted that. We don't know all the answers, but that doesn't mean the antimatter is evidence for a white hole.  

The universe is expanding with an accelerated speed. This requires energy to be added

No it doesn't. Think of the balloon analogy. The balloon is in a vacuum, and the pressure of the air inside is balanced by the tension in the skin. There's two ways to make it expand. One way is to blow more air into the balloon. That's like adding energy. But there's another way - reduce the tension. You make the skin weaker. Make it a bubble-gum balloon. 

We have never observed any singularity, so why should a black hole singularity exist?

Agreed. I don't think they do myself. Because a gravitational field is a place where the coordinate speed of light varies, and it can't go lower than zero. 

Information seems to be lost in a black hole singularity, which goes against the rules of quantum mechanics; a white hole would be a solution to this black hole information paradox.

There is no actual paradox. Whenever you see mention of a paradox, it means somebody doesn't understand something properly, that's all.  

Instead of erupting black holes, a white hole could fuel the fermi bubbles. 

The problem with that is that your pencil falls down, not up. 

Quasars are active galactic nuclei that can be 100 times brighter than the whole Milky Way. Quasar are currently believed to be made from the accretion disk of black holes, and they shoot out immense galactic jets, but the exact physics is unclear. 

Yes the exact physics is unclear, but that doesn't mean they're white holes. 

There is one solution that allows both Arp and science to be correct, that quasars are white holes connected to a wormhole, and we might be staring into another universe or optionally, another part of this universe.

I just don't buy things like wormholes. I know people like "exciting" things like wormholes and time travel and the multiverse, but there's just no evidence for such things. 

If there is a white hole in the center of the galaxy instead, the implications are enormous and it could give us answers to many grand problems in astrophysics.

I'm sorry to rain on your parade, but like I said at the beginning, I think white holes are a mathematical fantasy. 

A white hole or a black hole? That's the question!

And I think the answer is: black hole!  
A: I'd like to address the misconceptions in your quote from the wikipedia article.

”Like black holes, white holes have properties like mass, charge, and angular momentum. They attract matter like any other mass, but objects falling towards a white hole would never actually reach the white hole's event horizon"

They do "have" mass, charge, and angular momentum. But they are also over and done.
There are nice diagrams called Carter-Penrose diagrams or Penrose diagrams or just conformal diagrams. They diagram the regions of spacetime in question in a way that shows the causal structure quite well (so that you can see what can affect what) potentially have some extra events in the infinite distance, infinite past, or infinite future and more. And generally are designed to fit everything in a nice finite size picture. Here arr some examples from wikipedia (https://upload.wikimedia.org/wikipedia/en/thumb/f/f0/PENROSE2.PNG/660px-PENROSE2.PNG)

So let's look at the diagram for an "eternal" black hole (like the one on the upper left) with no charge, no angular momentum, and mass $M.$ Just because it is the simplest. It consists of a diamond with 45 degree sides that had he top and bottom chopped off by equal amounts so there is a nice 45 degree X connecting the four new corners created. The top line is the black hole singularity. The bottom line is the white hole singularity. The diamond to the right of the X is an external universe and the diamond to the left of the X is another external universe.
When I say external universe I mean it has a space that looks the region outside a black hole of surface area $4\pi(2MG)^2$ that has times that go from $t=-\infty$ all the way up to  $t=+\infty.$ A whole eternal universe fit into a diamond. Really every point is a time and a whole spherical shell of fixed radius. You just draw it so that times are radial lines through where the X has the center and you space out an infinite number of radial lines through the diamond. And surfaces of constant radius outside the black hole are hyperbolas that asymptotically approach the X. The X itself is at the surface of surface area $4\pi (2MG)^2.$
Why do we do this? Because it easily fits on a sheet of paper and light moves on 45 degree lines making it easy to see what affects what.
Why did I go to all this effort? Because you don't move towards a white hole, by definition.
Pick any event in the right diamond. Draw an X at 45 degrees with the cross at that point. That's how light goes. If you go more up than over you go less than lightspeed, and that is how you can move without breaking the laws of physics. You see that you can move towards the black hole singularity and you can move towards that original line from the original boundary of the diamond. You never ever ever ever move towards the white hole.
Even if you look back in time towards the white hole all the parts outside you see are themselves just points outside like any other which are points that could be reached by being farther outside farther back in time that got close before heading towards you.
So take a trip back in time heading towards the X, stop before you get to the X and then head away from the X you see that point is just someone that rushes towards the black hole, changes their mind and heads back out.
That point that is in your past that is closer to the event horizon is just a normal person rushing towards the black hole long ago that hadn't gotten close enough to cross yet.
That region to the right literally is the set of spatial points like $(x,y,z)$ with $x^2+y^2+z^2>2MG$ and times with $t\in (-\infty,+\infty).$ And absolutely every event is one that can only move towards the black hole singularity or move towards no singularity.
Nothing moves towards white hole event horizons from the outside. They are defined as surfaces that can only be crossed from the inside to the outside.
But remember when I said these diagrams compressed all the points into a finite picture but also added some extra points?  The white hole and it's event horizon ate extra points.
Those points are not in the future of any point in $(x,y,z)$ with $x^2+y^2+z^2>2MG$ and with times with $t\in (-\infty,+\infty).$ Not in the future of any of them, not a single one. So to any thing and any one outside the black hole event horizon, the white hole is in the past or elsewhen (which means in this case it is in the past of that whole other universe, the diamond to the left of the big X). And it will always be in your past (at best) and never your future.
So it is misleading to say that you move towards a white hole event horizon from the outside. By definition that is impossible since by definition it is a surface that you can only cross from inside to outside. And they aren't even really there, except in a picture.

but objects falling towards a white hole would never actually reach the white hole's event horizon"

You don't reach it because you aren't moving towards it because it in your past. You don't fall towards it. And that's why you don't reach it.
A: There are numerous misconceptions here, but allow me to address just a few:
Black holes do not have "appetite."  In order for an object to be consumed by a black hole, the object's trajectory would need to literally intersect with the event horizon (i.e. be on a collision course with it), otherwise the object will continue to orbit the black hole.  Because black holes are extremely compact, it actually makes it relatively difficult for orbiting objects to fall in. Instead, objects might come close to the black hole, and be accelerated to relativistic speeds, which accounts for the energetic phenomena that we observe in the vicinity of black holes. 
All of this applies to Sgr A*. Despite how massive it is, it's also very compact. This makes it a relatively rare event to observe a star (or a gas cloud) actually falling into it.

We observe a large cloud of antimatter in the galactic center...

The "cloud of antimatter" to which you refer is not a cloud of antimatter, but a cloud of matter with a smattering of positrons that is slightly greater than elsewhere in the interstellar medium. It's also not quite centered on Sgr A*. For a much more complete answer on this subject see https://physics.stackexchange.com/a/111758/10334.

The universe is expanding with an accelerated speed. This requires energy to be added, and if energy pours in through white holes, energy is added.

...but we don't observe any energy "pouring in" from Sag A*. Furthermore, we know that the repulsive force of dark energy is uniformly distributed throughout space, and not localized to centers of galaxies.

We have never observed any singularity, so why should a black hole
  singularity exist?

The singularity is, by definition, hidden inside the black hole, which is why we can never observe it.
A: I would have to conclude that it is a black hole most of the time. I would conjecture most of the time we observe a black hole with a very strong magnetic field in addition to its powerful gravitational field. The strong magnetic field can account for a number of the observations that were pointed out in your question. I prefer to refer to it as a "BlacktoWhite""MagneticGravitational" thermal equilibrium Galactic Center.


*

*The magnetic field character serves to explain the large Fermi Fields at the center of our galaxy that are observed by NASA's Fermi Telescope. The electrons and protons of the electron to photon and proton to proton interactions giving rise to the measured Gama Rays can be accounted for by the plasma flow and hypothesized spinning magnetic field vortex of this "Grey" hole. Together the gravitational force and the dynamically balanced magnetic forces can account for the presence and speed of the ionic particles necessary for the Gama & X-Ray Radiation. As the ions are drawn in by gravity they are also directed away from the center magnetically. 
Article supporting the large Magnetic field of SGR A*
http://blogs.discovermagazine.com/d-brief/2013/08/14/the-strong-magnetic-field-around-our-galaxys-black-hole/#.VgQwUMtViko
"This past spring, astronomers discovered PSR J1745-2900, and after making absolutely certain that they really had finally found a pulsar near Sgr A*, they began figuring out what the star has to say about the black hole. A paper in this week’s edition of Nature details how they discovered that a surprisingly strong, large scale magnetic field infuses the area around Sgr A*."
"A strong magnetic field around the supermassive black hole at the centre of the Galaxy"
From Paper Cited Below
http://www.nature.com/nature/journal/v501/n7467/full/nature12499.html
"Here we report multi-frequency radio measurements of a newly discovered pulsar close to the Galactic Centre9, 10, 11, 12 and show that the pulsar’s unusually large Faraday rotation (the rotation of the plane of polarization of the emission in the presence of an external magnetic field) indicates that there is a dynamically important magnetic field near the black hole. If this field is accreted down to the event horizon it provides enough magnetic flux to explain the observed emission—from radio to X-ray wavelengths—from the black hole."



Please see supporting Article : 
http://www.astronomy.com/news/2014/06/powerful-magnetic-fields-challenge-black-holes-pull
“When the infalling gas carries enough magnetic field in our simulations, then the magnetic field near the black hole gets stronger until it balances gravity," explains Alexander Tchekhovskoy of LBNL, a co-author of the study. “This fundamentally changes the behavior of the gas near the black hole.”
"The largest X-ray flare from the Milky Way's supermassive black hole has been detected.
Chandra caught this flare, which was 400 times brighter than the black hole's usual output, in September 2013.Researchers also saw a second large X-ray flare a little over a year later. Astronomers have two theories about what could be causing these "megaflares" from Sgr A*. The first idea is that the strong gravity around Sgr A* tore apart an asteroid in its vicinity, heating the debris to X-ray-emitting temperatures before devouring the remains. Their other proposed explanation involves the strong magnetic fields around the black hole. If the magnetic field lines reconfigured themselves and reconnected, this could also create a large burst of X-rays."
Source: http://chandra.harvard.edu/photo/2015/sgra/


*Observation a lot of antimatter near the center. 
The strong magnetic field of the "Grey" hole is probably providing the right conditions for the antimatter to be produced & preserved for relatively long time. Some how isolating it from matter thereby delaying its annihilation. The acceleration effects on pure energy that creates antimatter would probably be the result of the magnetic vortex and its changing EMF. The Magnetic Pulsing could result in accelerating {infinitely} very small masses or pure energy close to the speed of light at which point matter and antimatter could be the expected result set.


Supporting Article follows :
Trapping Antimatter with Magnets
"Researchers at the ALPHA experiment at CERN made major news today with the announcement that they’ve trapped antimatter atoms for 1,000 seconds. That’s more than 16 minutes and 5,000 times longer than their last published record of two tenths of a second."
They used special magnetic field structure to accomplish this.


*"Sagittarius A* don’t have any "appetite". less than 1 % is "eaten" by the black hole and more than 99 % is the ejected gas we observe. If Sag A* is a black hole it seems like there is some strange physics going on, if Sag A* is a white hole, ejection of material is what we would expect."


By mathematical definition a white hole is the mathematical reverse of a black hole. So if 1% of the cold gases are actually getting into SGR A* it would infer that it can not be a white hole by definition. Nothing can enter a white hole, matter and EM radiation can only leave it. But the fact that SGA A* is ingesting/accumulating mass does not preclude it could not become a white hole and may have done just this transition in the past a couple million years ago.
The Magnetic vortex or flux is often used to explain accretion jets or the departing matter and EMR from Black holes. Large Magnetic fields as found in SGR A* could
account for the hot gases being rejected close to the event horizon of this black hole.
As was observed in the G2 incident you reference above. 
"Observations with ALMA have detected a very strong magnetic field close to the black hole at the base of the jets and this is probably involved in jet production and collimation." 
Source: https://en.wikipedia.org/wiki/Supermassive_black_hole
While we are mentioning event horizons I think it is important to point out Super Massive black holes are very different than smaller black holes. Also their densities vary as well.
From : https://en.wikipedia.org/wiki/Supermassive_black_hole
"Supermassive black holes have properties that distinguish them from lower-mass classifications. First, the average density of a supermassive black hole (defined as the mass of the black hole divided by the volume within its Schwarzschild radius) can be less than the density of water in the case of some supermassive black holes.[5] This is because the Schwarzschild radius is directly proportional to mass, while density is inversely proportional to the volume. Since the volume of a spherical object (such as the event horizon of a non-rotating black hole) is directly proportional to the cube of the radius, the density of a black hole is inversely proportional to the square of the mass, and thus higher mass black holes have lower average density. In addition, the tidal forces in the vicinity of the event horizon are significantly weaker for massive black holes"
General belief it is a black hole. "No known astronomical object other than a black hole can contain 4.1 million M☉ in this volume of space."
Source : https://en.wikipedia.org/wiki/Supermassive_black_hole
"Astronomers are very confident that our own Milky Way galaxy has a supermassive black hole at its center, 26,000 light-years from the Solar System, in a region called Sagittarius A*[15] because:
The star S2 follows an elliptical orbit with a period of 15.2 years and a pericenter (closest distance) of 17 light-hours (1.8×1013 m or 120 AU) from the center of the central object.[16]
From the motion of star S2, the object's mass can be estimated as 4.1 million M☉,[17][18] or about 8.2×1036 kg.
The radius of the central object must be less than 17 light-hours, because otherwise, S2 would collide with it. In fact, recent observations from the star S14[19] indicate that the radius is no more than 6.25 light-hours, about the diameter of Uranus' orbit. However, applying the formula for the Schwarzschild radius yields just about 41 light-seconds, making it consistent with the escape velocity being the speed of light.
No known astronomical object other than a black hole can contain 4.1 million M☉ in this volume of space."
 


*Close to the galactic center we observe the formation of many new stars, it is the most massive breeding ground for new stars in the galaxy and a large area close to the galactic center is populated by young stars. A black hole would devour stars instead of giving birth to stars, while a white hole would give excellent conditions for star birth. Neither have we observed any star being devoured by Sag A*, or anything else, and we have observed it for 40 years.


Source : http://arxiv.org/abs/1303.3403
ALMA Observations of the Galactic Center: SiO Outflows and High Mass Star Formation near Sgr A*  "The SiO clumps are interpreted as highly embedded protostellar outflows, signifying an early stage of massive star formation near Sgr A* in the last 104−105 years." 
We can assume the star formations are taking place outside the event horizon since we are observing strong outflows of up to 99% of the gases. We would need to account for the observed SiO clump positons relative to the point of singularity to get a better handle on just where the new stars are forming. And the strong gravitation pull on the hot SiO gases not being ingested can account for the stars forming near the galatic center but outside the event horizon of the black hole. Again the magnetic field must be a large force in the new stars formations by helping to keep the hot gases to stay just out of the event horizon. 
In closing : Perhaps for every black hole there exists its reverse, its white hole.
Some how this seems intuitively correct since all the energy, matter and information entering a black hole needs to be conserved and probably needs to be returned to our universe albeit scrambled or at least to an alternative universe.
The more massive the black hole the more essential this becomes. Apparently the nature 
of the Black hole drops off dramatically as it becomes even more massive. It is interesting to note most super massive black holes have strong magnetic fields and weaker tidal forces at the event horizons and have a lower average density. A great number also emmit gamma and or x-ray jets and other gamma and x-ray distortions as well as Hawking radiation and radio waves. Apparently super massive black holes do a lot more than just draw in mass, energy and information never to be seen again once the event horizon is breached. Perhaps like many energetic systems there is a dissipation energy event that takes place in a black hole that necessitates its reverse to take over. Sort of a critical mass and at that point the balance tips to a white hole eruption phenomena.
Similar to a long contraction period with the accumulation of mass and then a short expansion period or burst of matter with the whole cycle taking place over a mega-annum. While the ongoing emissions over the long term can be due to the magnetic flux.
To be as complete as possible on this answer as time permits we should also mention the thermal equilibrium black hole model Steven Hawkins puts forth. 
"In quantum mechanics, the black hole emits Hawking radiation and so can come to thermal equilibrium with a gas of radiation. Because a thermal-equilibrium state is time-reversal-invariant, Stephen Hawking argued that the time reverse of a black hole in thermal equilibrium is again a black hole in thermal equilibrium.2 This may imply that black holes and white holes are the same object. The Hawking radiation from an ordinary black hole is then identified with the white-hole emission."
From : https://en.wikipedia.org/wiki/White_hole 

Source : http://astrobites.org/2013/09/08/chandra-observes-sgr-a-rejecting-material/
Figure 2 – The X-ray spectrum of Sgr A*. The left-hand plot shows a zero metallicity continuum fit with various Gaussian lines. The right-hand plot shows the fit of a model with nearly equal inflow and outflow rates.
"Sgr A* feeds off the winds of these stars. Wang et al. modeled the exact inflow rate of material, which leads to accretion onto the disk. The team found that the powerful inflow of stellar gas nearly balanced the outflow – existing in a state near equilibrium. This may be seen in the right-hand plot in Figure 2. In such a state, one can easily deduce why Sgr A* naturally has such low bolometric luminosity and a lack of powerful jets.
But while approximately 50% of the gas falls onto the accretion disk and funnels toward the event horizon, Sgr A* may not necessarily capture it. Wang et al. found that Sgr A* has difficulty in actually capturing these winds because of their high temperatures. They studied the relative strengths of individual emission lines, which are powerful diagnostics of the accretion flow and plasma temperature, and came to the conclusion that most of the gas is simply too hot to swallow.
Over the course of the observing campaign, Sgr A* rejected 99% of this material – letting only a small amount of cool gas in. In order to be captured by a black hole, material must lose heat and momentum. This can be accomplished by ejecting most of the gas, carrying away energy and momentum, in order to allow a small amount to reach the black hole itself."

Source:
https://www.cfa.harvard.edu/news/2012-16
"The central accretion disk can warp as it spirals in toward the black hole, under the influence of the black hole's spin," explained co-author Douglas Finkbeiner of the CfA. "The magnetic field embedded in the disk therefore accelerates the jet material along the spin axis of the black hole, which may not be aligned with the Milky Way."
The two structures also formed differently. The jets were produced when plasma squirted out from the galactic center, following a corkscrew-like magnetic field that kept it tightly focused. The gamma-ray bubbles likely were created by a "wind" of hot matter blowing outward from the black hole's accretion disk. As a result, they are much broader than the narrow jets.


*

*See more at: https://www.cfa.harvard.edu/news/2012-16#sthash.t2NpNFOV.dpuf
