November 25, 2009, 8:17 AM CT

About first black holes

The first large black holes in the universe likely formed and grew deep inside gigantic, starlike cocoons that smothered their powerful x-ray radiation and prevented surrounding gases from being blown away, says a newly released study led by the University of Colorado at Boulder.

The formation process involved two stages, said Mitchell Begelman, a professor and the chair of CU-Boulder's astrophysical and planetary sciences department. The predecessors to black hole formation, objects called supermassive stars, probably started forming within the first few hundred million years after the Big Bang some 14 billion years ago. A supermassive star eventually would have grown to a huge size -- as much as tens of millions of times the mass of our sun -- and would have been short-lived, with its core collapsing in just in few million years, he said.

In the newly released study to be published in Monthly Notices of the Royal Astronomical Society in London, Begelman calculated how supermassive stars might have formed, as well as the masses of their cores. These calculations allowed him to estimate their subsequent size and evolution, including how they ultimately left behind "seed" black holes.

Begelman said the hydrogen-burning supermassive stars would had to have been stabilized by their own rotation or some other form of energy like magnetic fields or turbulence in order to facilitate the speedy growth of black holes at their centers. "What's new here is we think we have found a new mechanism to form these giant supermassive stars, which gives us a new way of understanding how big black holes may have formed relatively fast," said Begelman......... Posted by: Sean      Read more         Source

November 17, 2009, 8:33 AM CT

Hidden Details in the Birth of Super-Suns

The constellation of Orion is a hotbed of massive star formation, most prominently in the Great Nebula that sits in Orion's sword. The glowing gas of the Nebula is powered by a group of young massive stars, but behind it is a cluster of younger stars and clumps of gas. Still gathering together under gravity's pull, these gas clumps will eventually ignite into stars.

The youthful cluster cannot be seen with traditional telescopes because of the surrounding gas and dust, but a new high-resolution time-lapse movie reveals the process of massive star formation with radio images a thousand times sharper and more detailed than any previously obtained. The movie shows that massive stars form like their smaller siblings, with disk accretion and magnetic fields playing crucial roles.

The way that massive stars form remains mysterious, in part, because massive stars are rare and tend to spend their youth enshrouded by dust and gas hiding them from view.

"We know how these stars die, but not how they are born," said Lincoln Greenhill, a principal investigator of the study and part of a team comprising researchers from the Harvard-Smithsonian Center for Astrophysics (CfA) and the National Radio Astronomy Observatory (NRAO).

Unlike Hubble and other visible-light telescopes, radio telescopes can penetrate dusty veils around stars. The research astronomers studied a massive young protostar called Source I (pronounced "eye") at radio wavelengths, using the National Science Foundation's Very Long Baseline Array (VLBA) as a powerful "zoom lens."........ Posted by: Sean      Read more         Source

November 2, 2009, 11:09 PM CT

Light On Longstanding Cosmic Mystery

An international collaboration that includes researchers from the University of Delaware's Bartol Research Institute in the Department of Physics and Astronomy has discovered very-high-energy gamma rays in the Cigar Galaxy (M82), a bright galaxy filled with exploding stars 12 million light years from Earth.

The gamma rays observed by the team have energies more than a trillion times higher than the energy of visible light and are the highest-energy photons ever detected from a galaxy undergoing large amounts of star formation.

The discovery, made from data taken over a two-year-long observing campaign by the VERITAS collaboration of more than 100 researchers from 22 different institutions in the United States, Ireland, United Kingdom, and Canada, appears in the Nov. 1 advance online edition of the scientific journal Nature.

VERITAS (Very Energetic Radiation Imaging Telescope Array System) is a gamma ray observatory located at the Fred Lawrence Whipple Observatory near Amado, Ariz.

The finding provides "good evidence" that exploding stars are the origin of cosmic rays, as per Jamie Holder, assistant professor of physics and astronomy at the University of Delaware and deputy spokesperson for the VERITAS collaboration.

Produced in violent processes in our own galaxy and beyond, cosmic rays are actually energetic particles that continually bombard Earth's atmosphere. They are important, Holder says, because they make up a large fraction of the energy budget of our galaxy, The Milky Way. The amount of energy in cosmic rays is comparable to the energy contained in both starlight, and in Galactic magnetic fields, Holder notes......... Posted by: Sean      Read more         Source

October 29, 2009, 10:28 PM CT

New Celestial Map Gives Directions for GPS

A number of of us have been rescued from unfamiliar territory by directions from a Global Positioning System (GPS) navigator. GPS satellites send signals to a receiver in your GPS navigator, which calculates your position based on the location of the satellites and your distance from them. The distance is determined by how long it took the signals from various satellites to reach your receiver.

The system works well, and millions rely on it every day, but what tells the GPS satellites where they are in the first place?.

"For GPS to work, the orbital position, or ephemeris, of the satellites has to be known very precisely," said Dr. Chopo Ma of NASA's Goddard Space Flight Center in Greenbelt, Md. "In order to know where the satellites are, you have to know the orientation of the Earth very precisely."

This is not as obvious as simply looking at the Earth - space is not conveniently marked with lines to determine our planet's position. Even worse, "everything is always moving," says Ma. Earth wobbles as it rotates due to the gravitational pull (tides) from the moon and the sun. Even apparently minor things like shifts in air and ocean currents and motions in Earth's molten core all influence our planet's orientation.

Just as you can use landmarks to find your place in a strange city, astronomers use landmarks in space to position the Earth. Stars seem the obvious candidate, and they were used throughout history to navigate on Earth. "However, for the extremely precise measurements needed for things like GPS, stars won't work, because they are moving too," says Ma......... Posted by: Sean      Read more         Source

October 14, 2009, 7:08 AM CT

The Milky Way's tiny neighbor

In the new ESO image, Barnard's Galaxy glows beneath a sea of foreground stars in the direction of the constellation of Sagittarius (the Archer). At the relatively close distance of about 1.6 million light-years, Barnard's Galaxy is a member of the Local Group (ESO 11/96), the archipelago of galaxies that includes our home, the Milky Way. The nickname of NGC 6822 comes from its discoverer, the American astronomer Edward Emerson Barnard, who first spied this visually elusive cosmic islet using a 125-millimetre aperture refractor in 1884.

Astronomers obtained this latest portrait using the Wide Field Imager (WFI) attached to the 2.2-metre MPG/ESO telescope at ESO's La Silla Observatory in northern Chile. Even though Barnard's Galaxy lacks the majestic spiral arms and glowing, central bulge that grace its big galactic neighbours, the Milky Way, the Andromeda and the Triangulum galaxies, this dwarf galaxy has no shortage of stellar splendour and pyrotechnics. Reddish nebulae in this image reveal regions of active star formation, where young, hot stars heat up nearby gas clouds. Also prominent in the upper left of this new image is a striking bubble-shaped nebula. At the nebula's centre, a clutch of massive, scorching stars send waves of matter smashing into the surrounding interstellar material, generating a glowing structure that appears ring-like from our perspective. Other similar ripples of heated matter thrown out by feisty young stars are dotted across Barnard's Galaxy......... Posted by: Sean      Read more         Source

October 7, 2009, 8:44 PM CT

New aluminum-water rocket propellant

Scientists are in the process of developing a new type of rocket propellant made of a frozen mixture of water and "nanoscale aluminum" powder that is more environmentally friendly than conventional propellants and could be manufactured on the moon, Mars and other water-bearing bodies.

The aluminum-ice, or ALICE, propellant might be used to launch rockets into orbit and for long-distance space missions and also to generate hydrogen for fuel cells, said Steven Son, an associate professor of mechanical engineering at Purdue University.

Purdue is working with NASA, the Air Force Office of Scientific Research and Pennsylvania State University to develop ALICE, which was used earlier this year to launch a 9-foot-tall rocket. The vehicle reached an altitude of 1,300 feet over Purdue's Scholer farms, about 10 miles from campus.

"It's a proof of concept," Son said. "It could be improved and turned into a practical propellant. Theoretically, it also could be manufactured in distant places like the moon or Mars instead of being transported at high cost".

Findings from spacecraft indicate the presence of water on Mars and the moon, and water also may exist on asteroids, other moons and bodies in space, said Son, who also has a courtesy appointment as an associate professor of aeronautics and astronautics......... Posted by: Sean      Read more         Source

October 6, 2009, 7:00 AM CT

The female astronaut

In the early years of the "space race" (1957-1975) two men sought to test a scientifically simple yet culturally complicated theory: that women might be innately better suited for space travel than men. In 1960 the thought of a woman in space was a radical one, and justifiably so. On the ground 75% of American women did not work outside the home and females were banned from military flight service altogether. In marriage, wives were mandatory to have their husband's permission to take out a bank loan, buy property, or purchase large household goods such as a refrigerator. Despite the social odds, a Harvard-educated surgeon and a U.S. Air Force General sought to determine if, from a purely practical perspective, women were suitable for space flight.

The latest look at the intersection of physiology, spaceflight and politics is captured in a new article entitled "A Forgotten Moment in Physiology: The Lovelace Woman in Space Program (1960-1962)," written by Kathy Ryan, Jack Loeppky and Donald Kilgore*. Their article appears in the September edition of Advances in Physiology (http://advan.physiology.org/cgi/reprint/33/3/157), a publication of the American Physiological Society (APS; www.the-aps.org/press). The APS has been an integral part of the scientific discovery process since it was founded in 1887......... Posted by: Sean      Read more         Source

September 30, 2009, 6:46 AM CT

Cosmic Rays Hit Space Age High

Planning a trip to Mars? Take plenty of shielding. As per sensors on NASA's ACE (Advanced Composition Explorer) spacecraft, galactic cosmic rays have just hit a Space Age high.

"In 2009, cosmic ray intensities have increased 19% beyond anything we've seen in the past 50 years," says Richard Mewaldt of Caltech. "The increase is significant, and it could mean we need to re-think how much radiation shielding astronauts take with them on deep-space missions".

The cause of the surge is solar minimum, a deep lull in solar activity that began around 2007 and continues today. Scientists have long known that cosmic rays go up when solar activity goes down. Right now solar activity is as weak as it has been in modern times, setting the stage for what Mewaldt calls "a perfect storm of cosmic rays".

"We're experiencing the deepest solar minimum in nearly a century," says Dean Pesnell of the Goddard Space Flight Center, "so it is no surprise that cosmic rays are at record levels for the Space Age".

Galactic cosmic rays come from outside the solar system. They are subatomic particles--mainly protons but also some heavy nuclei--accelerated to almost light speed by distant supernova explosions. Cosmic rays cause "air showers" of secondary particles when they hit Earth's atmosphere; they pose a health hazard to astronauts; and a single cosmic ray can disable a satellite if it hits an unlucky integrated circuit......... Posted by: Sean      Read more         Source

September 23, 2009, 7:19 AM CT

First Full Simulation of Star's Final Hours

The precise conditions inside a white dwarf star in the hours leading up to its explosive end as a Type Ia supernova are one of the mysteries confronting astrophysicists studying these massive stellar explosions. But now, a team of researchers, composed of three applied mathematicians at the U.S. Department of Energy's (DOE) Lawrence Berkeley National Laboratory and two astrophysicists, has created the first full-star simulation of the hours preceding the largest thermonuclear explosions in the universe.

In a paper to be reported in the recent issue of Astrophysical Journal, Ann Almgren, John Bell and Andy Nonaka of Berkeley Lab's Computational Research Division, with Mike Zingale of Stony Brook University and Stan Woosley of University of California, Santa Cruz, describe the first-ever three-dimensional, full-star simulations of convection in a white dwarf leading up to ignition of a Type Ia supernova. The project was funded by the DOE Office of Science.

Type Ia supernovae are of particular interest to astrophysicists as they are all thought to besurprisingly similar to each other, leading to their use as "standard candles" which researchers use to measure the expansion of the universe. Based on observations of these massive stellar explosions-a single supernova is as bright as an entire galaxy-researchers believe our universe is expanding at an accelerating rate. But what if Type Ia supernovae have not always exploded in the same way? What if they aren't standard?........ Posted by: Sean      Read more         Source

September 20, 2009, 7:04 PM CT

More to Solar Cycle than Sunspots

Challenging conventional wisdom, new research finds that the number of sunspots provides an incomplete measure of changes in the sun's impact on Earth over the course of the 11-year solar cycle. The study, led by researchers at the National Center for Atmospheric Research (NCAR) and the University of Michigan, finds that Earth was bombarded last year with high levels of solar energy at a time when the sun was in an uncommonly quiet phase and sunspots had virtually disappeared.

"The sun continues to surprise us," says main author Sarah Gibson of NCAR's High Altitude Observatory. "The solar wind can hit Earth like a fire hose even when there are virtually no sunspots".

The study, also written by researchers at NOAA and NASA, is being published recently in the Journal of Geophysical Research. It was funded by NASA and by the National Science Foundation, NCAR's sponsor.

"It is vitally important to realize that the 'quiet' sun really isn't all that quiet," says Rich Behnke, program director in NSF's Division of Atmospheric Sciences. "These high-speed streams of wind can affect a number of of our communications and navigation systems. And they can come at any time, during any part of the solar cycle".

Researchers for centuries have used sunspots, which are areas of concentrated magnetic fields that appear as dark patches on the solar surface, to determine the approximately 11-year solar cycle. At solar maximum, the number of sunspots peaks. During this time, intense solar flares occur daily and geomagnetic storms frequently buffet Earth, knocking out satellites and disrupting communications networks......... Posted by: Sean      Read more         Source