Thursday, June 28, 2012

Galaxy signed by 100 million years ago, still rings like a bell

An international team of astronomers that our Milky Way, was 100 million years ago, and that experience is still ringing like a bell in the form of a small galaxy or a massive dark matter as may be encountered with a recently discovered

Sloan Digital Sky Survey galaxy discovered near 300,000 (SDSS) is based on observations by a large way. The Milky Way contains a disk of about 20-30 kilometers per second, a big move up and down at a brisk 220 km per second at the center of the planets orbiting. This was very close to the position and speed at regular intervals as previously thought, according to the results of research to do.

"We are clearly in the plane of the Milky Way Galaxy, and a vertical rise above the bottom of the stellar distribution having the appearance of unexpected differences in the look - something that nobody has seen before, "said the Queen's University physicist Larry Widrow, lead researcher of the project

Researchers from the celestial object that is passed through the Milky Way has been able to find. This is a small satellite galaxy of our Milky Way has been the center, or an example of a dark matter halo as a near infra-structure that one can move. It may not be a single isolated incident in the past, and it may even be running

North and South Book Galaxy midplane researchers analyzed the distribution of small, but statistically significant differences detected SDSS data. More than a year, the asymmetry of the definition of the North seeking, but unable to solve a mystery. So they began to search for information about their events, the recent history of the Milky Way.

Scientists know that more than 20 visible satellite galaxy of the catch from one million to one billion solar masses from the public sphere with the center of the Milky Way. The satellite can make the invisible dark matter. In general, as the visible universe is dark matter, as there are six times. Astronomers computer simulations, that large-scale structure of the invisible things that move around our Milky Way is made available to hundreds.

Because of the abundance of the dark matter satellites, the satellite galaxy of the Milky Way is visible through the mid-plane and the vertical shear wave is probably

Computer simulations indicate that the next 100 million years or more, in our Milky Way "stop ringing." The North-South asymmetry and vertical motion of the stars disappear in the equilibrium orbit in the solar neighborhood do not go back again if we get hurt.

Tuesday, October 18, 2011

New Sun-bound probe

A NASA spacecraft set to launch in 2015 will come eight times closer to the Sun than any previous probe, operating within the star's scorching outer atmosphere, or corona. The $750 million Solar Probe will study the birthplace of the solar wind. During its expected seven-year lifetime, Solar Probe will make seven gravity slingshots around Venus, each time getting closer to the Sun. At its closest approach, it will orbit the Sun from within the outer part of the corona, at a distance of between 8 and 10 solar radii from the centre of the Sun. That is much closer than the previous record holder, the Helios spacecraft, which came within 67 solar radii of the star in the 1970s.Scientists hope the probe will help solve two enduring solar mysteries: Why is the Sun's outer atmosphere, or corona, so much hotter than its visible surface, which lies beneath it? And what accelerates the solar wind, a stream of charged particles from the Sun, to supersonic speeds? Heat shield: The idea of studying the Sun at close range was first proposed by the US National Academy of Science in 1958. But scientists have only recently been able to design heat shields for such a spacecraft within NASA's tight budgetary guidelines. The mini-bus sized Solar Probe will be protected from the Sun's fierce radiation by a disc-shaped, carbon-composite heat shield that will be 2.

The probe is 7 meters in diameter and about 15 centimeters thick. The heat shield technology is based on that used in Messenger, a NASA spacecraft that completed its first flyby of Mercury in January and that was also designed by engineers at APL. The side of the shield facing the Sun will heat up to 1400 °Celsius (2600 °F), while the instrument-carrying payload behind the shield will remain at room temperature.

New mystery on Mars

One of the supposedly best understood and least interesting landscapes on Mars is hiding something that could rewrite the planet's history. Or not. In fact, about all that is certain is that decades of assumptions regarding the wide, flat Hesperia Planum are not holding up very well under renewed scrutiny with higher-resolution, more recent spacecraft data.

"Most scientists don't want to work on the flat things," noted geologist Tracy Gregg of University at Buffalo, State University of New York. So after early Mars scientists decided Hesperia Planum looked like a lava-filled plain, no one really revisited the matter and the place was used to exemplify something rather important: The base of a major transitional period in the geologic time scale of Mars. The period is aptly called the Hesperian and it is thought to have run from 3.7 to 3.1 billion years ago.

But when Gregg and her student Carolyn Roberts started looking at this classic Martian lava plain with modern data sets, they ran into trouble.

"There's a volcano in Hesperia Planum that not many people pay attention to because it's very small," Gregg said. "As I started looking closer at the broader region -- I can't find any other volcanic vents, any flows. I just kept looking for evidence of lava flows. It's kind of frustrating. There is nothing like that in the Hesperia Planum."

"A likely cause of this trouble is the thick dust that blankets Hesperia Planum," she said. "It covers everywhere like a snowfall."

So she turned her attention to what could be discerned on Hesperia Planum: about a dozen narrow, sinuous channels, called rilles, just a few hundred meters wide and up to hundreds of kilometers long. These rilles have no obvious sources or destinations and it is not at all clear they are volcanic.

"The question I have is what made the channels," said Gregg. Was it water, lava, or something else? "There are some lavas that can be really, really runny. And both are liquids that run downhill." So either is a possibility.

To begin to sort the matter out, Gregg and Roberts are now looking for help on the Moon. Their preliminary findings are being presented at the Annual Meeting of The Geological Society of America in Minneapolis.

"On the Moon we see these same kinds of features and we know that water couldn't have formed them there," Gregg said. So they are in the process of comparing channels on the Moon and Mars, using similar data sets from different spacecraft, to see if that sheds any light on the matter. She hopes to find evidence that will rule out water or lava on Hesperia Planum.

"Everybody assumed these were huge lava flows," said Gregg. "But if it turns out to be a lake deposit, it's a very different picture of what Mars was doing at that time." It would also make Hesperia Planum a good place to look for life, because water plus volcanic heat and minerals is widely believed to be a winning combination for getting life started.

"The 'volcanic' part is an interpretation that's beginning to fall apart," said Gregg. "What is holding up is that the Hesperian marks a transition between the Noachian (a time of liquid water on the surface and the formation of lots of impact craters) and the Amazonian (a drier, colder Mars)."

She has found that other scientists are interested in her work because of its possible implications on the Mars geological time scale. Gregg is not worried that Mars history will need to be rewritten, but she does suspect that Hesperia Planum is a lot more complicated than people has long thought.

Friday, July 29, 2011

Getting Ready for ALMA’s First Scientific Observations

The first European antenna for the Atacama Large Millimeter/submillimeter Array (ALMA) has reached new heights, having been transported to the observatory's Array Operations Site (AOS) on 27 July 2011. The 12-metre diameter antenna has arrived at the Chajnantor plateau, 5000 metres above sea level. Here, it joins antennas from the other international ALMA partners, bringing the total number at the AOS to 16.

Although 16 sounds like just another number, it is the number of antennas specified for ALMA to begin its first science observations, and is therefore an important milestone for the project. Soon, astronomers will begin conducting new scientific research with ALMA.

The antenna, manufactured by the European AEM Consortium [1] under contract from ESO, was handed over to the observatory in April at the Operations Support Facility (OSF), after six months of testing. The OSF is at an altitude of 2900 metres in the foothills of the Chilean Andes. There, it was equipped with highly sensitive detectors, cooled by liquid helium, and other necessary electronics. Now, one of the giant ALMA transporter vehicles has taken it 28km further, along the dry desert road to the AOS. The AOS is the last port of call in a long journey that began when the component parts of the antenna were manufactured in factories across Europe, under the rigorous oversight of ESO.

The ALMA Antenna Project Manager at ESO, Stefano Stanghellini said, "It's great to see the first European ALMA antenna reach Chajnantor. It is from this arid plateau that these masterpieces of technology will be used to study the cosmos."

ALMA's Early Science observations are planned to begin later this year. Although ALMA will still be under construction, the 16-antenna array that will be available already outmatches all other telescopes of this kind. Astronomers from around the world have submitted almost 1000 proposals for Early Science observations. This level of demand is about nine times the number of observations that are expected be carried out during the first phase of Early Science, which demonstrates how excited researchers are to use ALMA, even at this early stage.

The final step from the OSF to the Chajnantor plateau is a relatively short journey, but for ALMA it makes a great difference. The plateau's elevated location -- 2100 metres higher than the OSF -- gives it the extremely dry conditions that are vital for observing at millimetre and submillimetre wavelengths, since these faint signals from space are easily absorbed by Earth's atmosphere.

While Chajnantor is perfect for ALMA, the extremely high altitude and lack of oxygen make it less pleasant for the site's human visitors. Although there is a Technical Building on Chajnantor -- it is in fact one of the highest buildings in the world -- the people working on ALMA do as much as possible from the lower altitude of the OSF, operating the telescope remotely.

When construction is completed in 2013, ALMA will have a total of 66 state-of-the-art antennas, which will work together as a single powerful telescope observing millimetre- and submillimetre-wavelength light. ALMA will help astronomers study the origins of planets, stars, galaxies and even the Universe itself, by observing cool molecular gas and dust in the Milky Way and beyond, as well as the relic radiation left over from the Big Bang.

ALMA, an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

Twenty-five European ALMA antennas, including this one, are being provided by ESO through a contract with the European AEM Consortium. ALMA will also have 25 antennas provided by North America, and 16 by East Asia.

Eclipses Yield First Images of Elusive Iron Line in the Solar Corona

Solar physicists attempting to unlock the mysteries of the solar corona have found another piece of the puzzle by observing the sun's outer atmosphere during eclipses.

Ground-based observations reveal the first images of the solar corona in the near-infrared emission line of highly ionized iron, or Fe XI 789.2 nm. The observations were taken during total solar eclipses in 2006, 2008, and 2009 by astrophysicist Adrian Daw of NASA's Goddard Space Flight Center in Greenbelt, Md., with an international team of scientists led by Shadia Habbal from the University of Hawaii's Institute for Astronomy (IfA).

"The first image of the corona in Fe XI 789.2 nm was taken during the total solar eclipse of March 29, 2006," said Daw.

The images revealed some surprises. Most notably, that the emission extends out at least three solar radii -- that's one-and-a-half times the sun's width at its equator, or middle -- above the surface of the sun, and that there are localized regions of enhanced density for these iron ions.

Combined with observations of other iron charge states, the observations yield the two-dimensional distribution of electron temperature and charge-state measurements for the first time, and establish the first direct link between the distribution of charge states in the corona and in interplanetary space. "These are the first such maps of the 2-D distribution of coronal electron temperature and ion charge state," said Daw.

Mapping the distribution of electron temperature and iron charge states in the corona with total solar eclipse observations represents an important step in understanding the solar corona and how space weather impacts Earth.

The scientists' results will be presented at the American Astronomical Society meeting on January 4 in Washington and published in the January issue of the Astrophysical Journal.