söndag 14 november 2010

More about galactic tornados.

Picture: NASA/JPL-Caltech/UCLA
Ucla, newsroom Astronomers report an unprecedented elongated double helix nebula near the center of our Milky Way galaxy. The part of the nebula the astronomers observed stretches 80 light years in length. "We see two intertwining strands wrapped around each other as in a DNA molecule," said Mark Morris. "Nobody has ever seen anything like that before in the cosmic realm. Most nebulae are either spiral galaxies full of stars or formless amorphous conglomerations of dust and gas — space weather. What we see indicates a high degree of order." The double helix nebula is approximately 300 light years from the enormous black hole at the center of the Milky Way. (The Earth is more than 25,000 light years from the black hole at the galactic center.)

This new gamma ray went 25000 lightyears to both sides.

"We know the galactic center has a strong magnetic field that is highly ordered and that the magnetic field lines are oriented perpendicular to the plane of the galaxy," Morris said. "If you take these magnetic field lines and twist them at their base, that sends what is called a torsional wave up the magnetic field lines.
"You can regard these magnetic field lines as akin to a taut rubber band," Morris added. "If you twist one end, the twist will travel up the rubber band."
"We see this twisting torsional wave propagating out. We don't see it move because it takes 100,000 years to move from where we think it was launched to where we now see it, but it's moving fast — about 1,000 kilometers per second — because the magnetic field is so strong at the galactic center — about 1,000 times stronger than where we are in the galaxy's suburbs." A strong, large-scale magnetic field can affect the galactic orbits of molecular clouds by exerting a drag on them. It can inhibit star formation, and can guide a wind of cosmic rays away from the central region; understanding this strong magnetic field is important for understanding quasars and violent phenomena in a galactic nucleus. This magnetic field is strong enough to cause activity that does not occur elsewhere in the galaxy; the magnetic energy near the galactic center is capable of altering the activity of our galactic nucleus. All galaxies that have a well-concentrated galactic center may also have a strong magnetic field at their center.
The magnetic field at the galactic center, though 1,000 times weaker than the magnetic field on the sun, occupies such a large volume that it has vastly more energy than the magnetic field on the sun. It has the energy equivalent of 1,000 supernovae.
What launches the wave, twisting the magnetic field lines near the center of the Milky Way? Morris thinks the answer is not the monstrous black hole at the galactic center, at least not directly.
Orbiting the black hole like the rings of Saturn, several light years away, is a massive disk of gas called the circumnuclear disk; Morris hypothesizes that the magnetic field lines are anchored in this disk. The disk orbits the black hole approximately once every 10,000 years.
"Once every 10,000 years is exactly what we need to explain the twisting of the magnetic field lines that we see in the double helix nebula," Morris said.
Published in Nature.
UCLA astronomers present the first evidence that tens of thousands of black holes are orbiting the monstrous black hole at the center of the Milky Way. The supermassive black hole, with a mass more than 3 million times that of our sun, is in the constellation of Sagittarius.

How were millions of young stars able to form at the center of our Milky Way galaxy in the presence of an enormous black hole with a mass 4 million times that of the sun? Millions of young stars packed closely together in this region are obscured by enormous quantities of dust but are easier to observe in the infrared because infrared light can penetrate the dust. More star formation is occurring in this region than anywhere else in the galaxy.

The Milky Way has "a wimpy galactic center," according to Becklin, who noted that while black holes in the center of other galaxies can be up to billions of times the mass of our sun, ours is only some 4 million times as massive. "Our previous assumption was that the black hole would make that star formation next to impossible; the tidal forces would not allow the collapse of a cloud of gas and dust to form a star. But it's happening, within just a light year of the black hole," said Mark Morris. "We are trying to understand, through observations using both short and long infrared wavelengths, what happens to the dust and gas that allows stars to form. We have some ideas.""We can study the dust and see what it is made of, and by knowing what it is made of and how big the dust grains are, we can model the evolutionary history of the dust and determine its fate. Most of the energy coming from the galactic center comes from the dust. The dust absorbs starlight and reemits it as infrared; that's why we are observing it in the infrared. We study the energy pouring out of the galactic center by analyzing the dust."
The amount of dust in the galactic center, which is approximately 500 light years across, is approximately 1 million times the mass of our sun, Morris said. Star formation is strongly affected by the presence of a magnetic field. A strong enough magnetic field can prevent a cloud from collapsing to form a star, Morris said.

UCLA astronomers report that three stars have accelerated by more than 250 thousand miles per hour per year as they orbit the monstrous black hole at the center of our Milky Way galaxy. "We are actually seeing stars begin to curve in their orbits," Ghez said. "One of these stars may complete its orbit around the supermassive black hole in as little as 15 years. The two closest stars are only 10 light days from the black hole, but Ghez predicts they will orbit the enormous black hole and not be swallowed by it. In 1995 the three stars were moving at two million miles per hour, and by 1999 they had changed their velocities by more than one million miles per hour.

UCLA astronomers report they have detected remarkably stormy conditions in the hot plasma being pulled into the monstrous black hole residing at the center of our Milky Way galaxy. The black hole is dining on a calm stream of plasma that experiences glitches only 2 percent of the time," said Andrea Ghez, professor of physics and astronomy at UCLA, who headed the research team. "Our infrared detection shows for the first time that the black hole's meal is more like the Grand Rapids, in which energetic glitches from shocked gas are occurring almost continually."

Animation of the stellar orbits in the central parsec. Images taken from the years 1995 through 2008 are used to track specific stars orbiting the proposed black hole at the center of the Galaxy.

UCLA and Japan have discovered evidence of "natural nuclear accelerators" at work in our Milky Way galaxy. Cosmic rays of the highest energies were believed by physicists to come from remote galaxies containing enormous black holes capable of consuming stars and accelerating protons at energies comparable to that of a bullet shot from a rifle. These protons — referred to individually as "cosmic rays" — travel through space and eventually enter our galaxy. But earlier this year came a surprising discovery: Many of the energetic cosmic rays found in the Milky Way are not actually protons but nuclei — and the higher the energy, the greater the nuclei-to-proton ratio. "This finding was totally unexpected because the nuclei, more fragile than protons, tend to disintegrate into protons on their long journey through space," said Alexander Kusenko. Stellar explosions in our own galaxy can accelerate both protons and nuclei. But while the protons promptly leave the galaxy, the heavier and less mobile nuclei become trapped in the turbulent magnetic field and linger longer, the local density of nuclei is increased, and they bombard Earth in greater numbers. These ultra–high-energy nuclei have been trapped in the web of galactic magnetic fields for millions of years, and their arrival directions as they enter the Earth's atmosphere have been "completely randomized by numerous twists and turns in the tangled field," he said.
published Aug. 20 in the journal Physical Review Letters.

The fascinating radio image of Messier 87 (above) was taken with the Very Large Array (VLA) at a frequency of 327 MHz (millions of cycles per second), corresponding to a wavelength of about 92 cm. The brightest radio emission is shown in red, and shows a central peak at the same position as M87. There are also jets of emission extending to the west and to the east, producing large radio lobes (yellow). Note that the western lobe (to the right) takes a sudden turn to the south (bottom), suggesting that it is ramming into a denser and unseen intracluster medium.

A large halo of radio emission (green) surrounds the entire galaxy and jets. The halo stretches across a distance of about 80 kiloparsecs, more than twice the diameter of our own Milky Way Galaxy. The central galaxy and its radio halo, meanwhile, are immersed in an even larger cocoon of hot and thin gas which can be seen at x-ray wavelengths.

The VLA radio telescope team in New Mexico plotted the electrical system at the centre of the Milky Way. One scientist likened the giant plasma loops found there to a dynamo. With the more recent discovery of plasma jets from the same vicinity there is good reason to connect the two, since electricity is known to be able to bring about nuclear fusion, if not the creation of matter. (BBC News website 17 April 2000)

3 Aug 2010 : We find two red clump (RC) populations co-existing in the same fields toward the Galactic bulge. We can only understand the data if these RC peaks simply reflect two stellar populations separated. Most of our fields show the two RCs at roughly constant distance with longitude, which is also inconsistent with a tilted bar, although an underlying bar may be present. The stellar densities in the two RCs changes dramatically with longitude: on the positive longitude side the foreground RC is dominant, while the background RC dominates negative longitudes. A line connecting the maxima of the foreground and background populations is tilted to the line of sight by ~20 +/-4 deg., similar to claims for the tilt of a Galactic bar. The distance between the two RCs decreases towards the Galactic plane; seen edge-on the bulge is X-shaped, resembling some extra-galactic bulges and the results of N-body simulations. The center of this X is consistent with the distance to the Galactic center. Our observations may be understood if the two RC populations emanate, nearly tangentially, from the ends of a Galactic bar, each side shaped like a funnel or horn. Alternatively, the X, or double funnel shape, may continue to the Galactic center. This would appear peanut/box shaped from the Solar direction, but X-shaped when viewed tangentially.

Blueshifted stars are concentrated around the galactic center. The coordinate system has its origin at the Galactic center, composed of all stars (left-hand and right-hand panels) simultaneously. The upper right-hand panel shows the line-of-sight velocity distribution as a function of distance from the Sun d, while the lower right-hand panel is the cumulative distribution of BHB stars with distance from the Galactic center. With image.

Results from the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) experiment and from the Fermi space telescope suggest a local excess positron fraction e+/(e+ + e−) at energies above 10 GeV as well as an excess of e+ + e− peaking around
500 GeV. An attractive explanation is that a DM WIMP (weakly interacting massive particle) is present in our galaxy at large enough concentrations to self-annihilate into standard model leptons.

Antimatter is blueshifted and with R-parity? Antimatter is also dark matter? Has an collission between matter and antimatter happened? Is that what we see as the enormous gamma radiation burst?

An unusual distribution of Gamma Ray energy, shown in this figure as the red glow above the Milky Way plane. It has been interpreted as a region in which antimatter (electrons are positively charged [positrons] and protons have a negative charge) has interacted with conventional matter, releasing a huge amount of energy.

"Nothing we tried besides dark matter came anywhere close to being able to accommodate the features of the observation," Dan Hooper, of the Fermi National Accelerator Laboratory in Batavia, Ill., and the University of Chicago, told SPACE.com. "It's always hard to be sure there isn't something you just haven't thought of. But I've talked to a lot of experts and so far I haven't heard anything that was a plausible alternative."
Hooper conducted the analysis with Lisa Goodenough. They think the Milky Way's gamma-ray glow is caused by dark matter explosions.
By studying the data on this radiation, Hooper and Goodenough calculated that dark matter must be made of particles called WIMPs (weakly interacting massive particles) with masses between 7.3 and 9.2 GeV (giga electron volts) — almost nine times the mass of a proton. They also calculated a property known as the cross-section, which describes how likely the particle is to interact with others.
Knowing these two properties would represent a huge leap forward in our understanding of dark matter.
"It's the biggest thing that's happened in dark matter since we learned it existed," Hooper said. "So long as no unexpected alternative explanations come forward, I think yes, we've finally found it."

3 kommentarer:

  1. More information
    15.11.10 Gamma rays are the highest-energy form of light. Other astronomers studying gamma rays hadn't detected the bubbles partly because of a fog of gamma rays that appears throughout the sky. The fog happens when particles moving near the speed of light interact with light and interstellar gas in the Milky Way.
    The bubble emissions are much more energetic than the gamma-ray fog seen elsewhere in the Milky Way. The bubbles also appear to have well-defined edges. The structure's shape and emissions suggest it was formed as a result of a large and relatively rapid energy release.

    In many other galaxies, astronomers see fast particle jets powered by matter falling toward a central black hole. While there is no evidence the Milky Way's black hole has such a jet today, it may have in the past. The bubbles also may have formed as a result of gas outflows from a burst of star formation, perhaps the one that produced many massive star clusters in the Milky Way's center several million years ago.

    Electrons moving near the speed of light are an important source of the Milky Way's diffuse gamma-ray glow; they also power a new galactic structure uncovered in Fermi data. When a relativistic electron strikes a low-energy (radio or infrared) photon, the collision slightly slows the electron and ramps up the photon to gamma-ray energies.

    The bubbles display a much more energetic ("harder") spectrum (left), with peak energies around 10 GeV, than the diffuse gamma-ray glow. the electrons responsible for the bubble emission must have energies greater than 500 GeV.

  2. A video is seen here

  3. http://matpitka.blogspot.com/2010/11/what-might-be-origin-of-fermi-bubbles.html
    The Planck constant change make antimatter invisible?

    I would rather compare it to a superconductive state. Also usual tornados can have strange effects (of superconduction, dark matter?).