Simulation to create a Milky Way-like galaxy. Supercomputer experiment supports cosmological model of a "cold dark matter" universe After nine months of number-crunching on a powerful supercomputer, a beautiful spiral galaxy matching our own Milky Way emerged from a computer simulation of the physics involved in galaxy formation and evolution. The simulation by researchers at the University of California, Santa Cruz, and the Institute for Theoretical Physics in Zurich solves a longstanding problem that had led some to question the prevailing cosmological model of the universe.
"Previous efforts to form a massive disk galaxy like the Milky Way had failed, because the simulated galaxies ended up with huge central bulges compared to the size of the disk," said Javiera Guedes, who recently earned her Ph.D. in astronomy and astrophysics at UC Santa Cruz and is first author of a paper on the new simulation, called "Eris. " The paper has been accepted for publication in the Astrophysical Journal. Hubble Heritage Gallery Images. Out-of-This-World Hypothesis: Cosmic Forces Control Life on Earth.
The rise and fall of species on Earth might be driven in part by the undulating motions of our solar system as it travels through the disk of the Milky Way, scientists say. Two years ago, scientists at the University of California, Berkeley found the marine fossil record shows that biodiversity-the number of different species alive on the planet-increases and decreases on a 62-million-year cycle. At least two of the Earth's great mass extinctions-the Permian extinction 250 million years ago and the Ordovician extinction about 450 million years ago-correspond with peaks of this cycle, which can't be explained by evolutionary theory.
Now, a team of researchers at the University of Kansas (KU) have come up with an out-of-this-world explanation. Their idea hinges upon the fact that, appearances aside, stars are not fixed in space. They move around, sometimes rushing headlong through galaxies, or approaching close enough to one another for brief cosmic trysts. Galactic bow shock. Active galactic nucleus. Models of the active nucleus[edit] Accretion disc[edit] In the standard model of AGN, cold material close to a black hole forms an accretion disc. Dissipative processes in the accretion disc transport matter inwards and angular momentum outwards, while causing the accretion disc to heat up. The expected spectrum of an accretion disc peaks in the optical-ultraviolet waveband; in addition, a corona of hot material forms above the accretion disc and can inverse-Compton scatter photons up to X-ray energies. The radiation from the accretion disc excites cold atomic material close to the black hole and this in turn radiates at particular emission lines.
A large fraction of the AGN's radiation may be obscured by interstellar gas and dust close to the accretion disc, but (in a steady-state situation) this will be re-radiated at some other waveband, most likely the infrared. Relativistic jets[edit] Radiatively inefficient AGN[edit] Observational characteristics[edit] Types of active galaxy[edit] Cosmology - Galaxies. We already met our Milky Way galaxy in the Our Galaxy section. We also discussed stars which are members of galaxies. Most of the beautiful phenomenon we see in the night sky - comets, planets, star clusters, planetary nebula and diffuse nebula - are all around or within our own galaxy.
Beyond our galaxy are other interesting phenomenon: A variety of other galaxies Clusters of galaxies - covered in their own section Supercluster of galaxies - covered in their own section Active Galactic Nuclei Cosmic Background Radiation - covered in The Big Bang By studying these galaxies and their motion relative to us and each other we learn about how our Universe was formed.
What we know about galaxies gives vital clues as to how the Universe began. It has been recently discovered that while there are a few spiral galaxies in the early Universe, the majority of galaxies are elliptical. There is a variety of galaxies, all with different sizes and shapes. (Image Credit) A galactic comparison: Back to Top. Seeing Circuits (2) Jan 13, 2005 Seeing Circuits (2) In Part 1 we listed some of the effects of circuits in space and noted that they were all power-consuming effects. We asked: Where is the power source? The power could be generated locally. The rotational inertia of a body could drive the circuit in much the same way as a water-driven turbine in a dam drives a generator. Early plasma physicists often simply assumed such a mechanism. But because smaller-scale circuits in space are invariably coupled to larger-scale circuits (such as the coupling between the auroral circuit and the "solar wind" circuit), the Electric Universe posits a remote power supply.
An electrical current in plasma will generate its own magnetic field and "self constrict" the current channel. These cables have been identified running from equator to poles in the circuits that power the aurora. If all these filaments are Birkeland currents, they are only the visible portions of entire circuits. Galactic magnetic fields. Introduction Magnetic fields are a major agent in the interstellar medium (ISM) of spiral, barred and irregular galaxies.
They contribute significantly to the total pressure which balances the ISM against gravity. They may affect the gas flows in spiral arms, around bars and in galaxy halos. Magnetic fields are essential for the onset of star formation as they enable the removal of angular momentum from the protostellar cloud during its collapse. MHD turbulence distributes energy from supernova explosions within the ISM. Magnetic reconnection is a possible heating source for the ISM and halo gas. Magnetic fields also control the density and distribution of cosmic rays in the ISM. Galactic magnetic fields can be observed in the optical range via starlight which is polarized by interstellar dust grains in the foreground. At short radio wavelengths the orientation of the observed polarization vectors is perpendicular to the field orientation. The Origin of Galactic Magnetic Fields References. Galaxies, bar glaxy, the milky way, and our solar system. Zooming Out of our galaxy.
After a 14-Year Search --Elusive Ancient Galaxy Found. In the Hubble Deep Field Region of the Universe (above), an international team of astronomers managed for the first time to determine the distance of the galaxy HDF850.1, well-known among astronomers as being one of the most productive star-forming galaxies in the observable universe. The galaxy is at a distance of 12.5 billion light years when the universe was less than 10 percent of its current age. For the past 14 years, HDF850.1 has remained strangely elusive. Its location in space, specifically its distance from Earth – the subject of many studies – ultimately remained unknown. How was that possible? "A vast cloud of dust keeps HDF850.1 hidden from telescopes searching the universe in the visible light range, so even the Hubble Space Telescope can't see it," Robertson said.
"If it wasn't for the dust layer, this galaxy would shine bright and blue with the intense light from the newly forming stars. " The galaxy HDF850.1 was discovered in 1998. Journal reference: Nature. Galaxy Colonization. Science with Out of this World Info. Daily Galaxy.
The Scale of Things. The Milky Way. Dim Matter. Colliding Galaxies. There are many instances where galaxies appear to be interacting with each other enough to cause obvious distortions of the galaxies that interact. These interactions may have a significant connections with the manner in which galaxies evolve with time. Example: Arp 273 Interacting Galaxies The adjacent pair of interacting spiral galaxies in the constellation Andromeda at a distance of about 200 million light years is called Arp 273 (Source). The larger galaxy at the upper left is strongly tidally distorted. The companion (seen edge-on in the lower right) exhibits a relatively undisturbed spiral disk, but a luminous, star burst nucleus (one in which there is a burst of new star formation). SOURCE: CREDIT: National Optical Astronomy Observatories Example: A Fiery Galactic Collision The ring is a wave of star formation traveling outwards at about 200,000 miles per hour that would not be there if the galaxy had not collided with another.