Archive for April 3, 2013

NGC 602: Taken Under The “Wing” Of The Small Magellanic Cloud

Credit: X-ray: NASA/ CXC/ Univ.Potsdam/ L.Oskinova et al; Optical: NASA/STScI; Infrared: NASA/JPL-Caltech

Credit: X-ray: NASA/ CXC/ Univ.Potsdam/ L.Oskinova et al; Optical: NASA/STScI; Infrared: NASA/JPL-Caltech

The Small Magellanic Cloud (SMC) is one of the Milky Way’s closest galactic neighbors. Even though it is a small, or so-called dwarf galaxy, the SMC is so bright that it is visible to the unaided eye from the Southern Hemisphere and near the equator. Many navigators, including Ferdinand Magellan who lends his name to the SMC, used it to help find their way across the oceans.

Modern astronomers are also interested in studying the SMC (and its cousin, the Large Magellanic Cloud), but for very different reasons. Because the SMC is so close and bright, it offers an opportunity to study phenomena that are difficult to examine in more distant galaxies.

New Chandra data of the SMC have provided one such discovery: the first detection of X-ray emission from young stars with masses similar to our Sun outside our Milky Way galaxy. The new Chandra observations of these low-mass stars were made of the region known as the “Wing” of the SMC. In this composite image of the Wing the Chandra data is shown in purple, optical data from the Hubble Space Telescope is shown in red, green and blue and infrared data from the Spitzer Space Telescope is shown in red.

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Astrophysicists To Probe Dark Matter In Sunny California

April 3, 2013 1 comment

Uncloaking the secrets of dark matter in the universe is a cosmological conundrum puzzling some of the brightest astrophysicists. An upcoming conference, sponsored by the American Astronomical Society and organized by Rochester Institute of Technology professor Sukanya Chakrabarti, will probe the mass that does not absorb or emit light, and which is never seen, only inferred by its gravitational effects on other objects.

“The idea is to bring together people working on different probes of dark matter from dynamics, which is my area, to gravitational lensing, to indirect probes of dark matter like gamma ray radiation and to get everyone together,” says Chakrabarti, assistant professor in RIT’s School of Physics and Astronomy.

Computational astrophysicist Chakrabarti developed the “tidal analysis” method for probing dark matter while on a post-doctoral fellowship at UC Berkeley in 2009. An observational data set of the Milky Way compiled by a graduate student inspired her current research.

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AMS Experiment Measures Antimatter Excess In Space

The international team running the Alpha Magnetic Spectrometer (AMS1) today announced the first results in its search for dark matter. The results, presented by AMS spokesperson Professor Samuel Ting in a seminar at CERN2, are to be published in the journal Physical Review Letters. They report the observation of an excess of positrons in the cosmic ray flux.

The AMS results are based on some 25 billion recorded events, including 400,000 positrons with energies between 0.5 GeV and 350 GeV, recorded over a year and a half. This represents the largest collection of antimatter particles recorded in space. The positron fraction increases from 10 GeV to 250 GeV, with the data showing the slope of the increase reducing by an order of magnitude over the range 20-250 GeV. The data also show no significant variation over time, or any preferred incoming direction. These results are consistent with the positrons originating from the annihilation of dark matter particles in space, but not yet sufficiently conclusive to rule out other explanations.

“As the most precise measurement of the cosmic ray positron flux to date, these results show clearly the power and capabilities of the AMS detector,” said AMS spokesperson, Samuel Ting. “Over the coming months, AMS will be able to tell us conclusively whether these positrons are a signal for dark matter, or whether they have some other origin.”

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What Is Behind Einstein’s Turbulences?

© D. Radice, L. Rezzolla (AEI)

© D. Radice, L. Rezzolla (AEI)

The American Nobel Prize Laureate for Physics Richard Feynman once described turbulence as “the most important unsolved problem of classical physics”, because a description of the phenomenon from first principles does not exist. This is still regarded as one of the six most important problems in mathematics today. David Radice and Luciano Rezzolla from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute / AEI) in Potsdam have now taken a major step towards solving this problem: For the first time, a new computer code has provided relativistic calculations that give scientists a better understanding of turbulent processes in regimes that can be found in astrophysical phenomena.

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Understanding The Turbulence Of Gases In Planet-Forming Protoplanetary Disks

Many newly formed stars are surrounded by what are called protoplanetary disks, swirling masses of warm dust and gas that can constitute the core of a developing solar system. Proof of the existence of such disks didn’t come until 1994, when the Hubble telescope examined young stars in the Orion Nebula.

Protoplanetary disks may potentially become celestial bodies such as planets and asteroids. But just how they make that transformation will remain a mystery to science until researchers can get a grasp on the disordered movement, or turbulence, that characterizes the constituent gases of the disks. Turbulence is what some people regard as “the last great classical physics problem.”

“By understanding the nature of the gases, we can learn something about how small particles interact with each other, coagulate to become larger particles and then ultimately form planets,” says Jake Simon of the University of Colorado, principal investigator of a research project currently taking on two primary challenges in the quest to understand protoplanetary disk turbulence.

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Pre-Existing Mineralogy May Survive Lunar Impacts

Large impacts on the Moon can form wide craters and turn surface rock liquid. Geophysicists once assumed that liquid rock would be homogenous when it cooled. Now researchers have found evidence that pre-existing mineralogy can survive impact melt.

The researchers have discovered a rock body with a distinct mineralogy snaking for 18 miles across the floor of Copernicus crater, a 60-mile-wide hole on the Moon’s near side. The sinuous feature appears to bear the mineralogical signature of rocks that were present before the impact that made the crater.

The deposit is interesting because it is part of a sheet of impact melt, the cooled remains of rocks melted during an impact. Geologists had long assumed that melt deposits would retain little pre-impact mineralogical diversity.

“The takeaway here is that impact melt deposits aren’t bland,” said Deepak Dhingra, a Brown graduate student who led the research. “The implication is that we don’t understand the impact cratering process quite as well as we thought.”

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