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Hubble Sees Faintest Stars
ancient globular star cluster NGC 6397
Globular clusters are spherical concentrations of hundreds of thousands of stars. Seeing the whole range of stars in this area will yield insights into the age, origin, and evolution of the cluster.
These clusters formed early in the 13.7-thousand-million-year-old universe. The cluster observed by Hubble, called NGC 6397, is one of the closest globular star clusters to Earth.
Although astronomers have conducted similar observations since Hubble was launched, a team led by Harvey Richer of the University of British Columbia, Vancouver, is reporting that they have at last unequivocally reached the faintest stars. Richer's team announced their findings on 17 August at the 2006 International Astronomical Union General Assembly in Prague, Czech Republic, and in the 18 August edition of the journal Science.
"We have run out of hydrogen-burning stars in this cluster. There are no fainter such stars waiting to be discovered," said Richer. "We have discovered the lowest-mass stars capable of supporting stable nuclear reactions in this cluster. Any less massive ones faded early in the cluster's history and by now are too faint to be observed".........
Posted by: Sean Permalink Source
Astronomers proclaim Pluto is a planet
And it's about to be joined by several more, thanks to a new definition of the word "planet" announced recently by the world's astronomers through the International Astronomical Union (IAU).
The seven-person international panel that spent two years defining the difference between planets and smaller "solar system bodies" such as comets and asteroids includes an MIT astronomer.
If the definition is approved this week at the IAU General Assembly in Prague, our solar system will include 12 planets, with more to come. They include the eight classical planets that dominate the system, three planets in a new and growing category of "plutons" - Pluto-like objects - and Ceres. Pluto remains a planet and is the prototype for the new category of plutons.
"It's time to rewrite the textbooks," said Richard Binzel, an MIT professor of planetary science in the Department of Earth, Atmospheric and Planetary Sciences.
As per the new draft definition, two conditions must be satisfied for an object to be called a planet. First, the object must be in orbit around a star, while not being itself a star. Second, the object must be large enough (or, to be more technically correct, massive enough) for its own gravity to pull it into a nearly spherical shape.........
Posted by: Sean Permalink Source
Stellar Pinwheels At Our Galaxy's Core
A multinational team led by Peter Tuthill of the University of Sydney in Australia, used the extraordinary resolution of the 10-meter telescope at the W.M. Keck Observatory in Hawaii, to determine the nature of the enigmatic objects. They report their findings in the Aug. 18 issue of the journal Science.
Until these observations, researchers had not known whether the extremely red "cocoon" quintuplets were aging stars surrounded by shells of dust, or young stars accompanied by disks of bright gas. Neither hypothesis was convincing, and neither fully explained the enormous light output: Each quintuplet emits 10,000 to 100,000 times as much radiation as the Sun.
The new findings indicate the quintuplets are members of a rare class called "Wolf-Rayet colliding-wind binaries" -- massive, fast-burning star pairs that live only a few million years before exploding in terminal supernovae. By contrast, the Sun is about 5 billion years old and only middle-aged. The pinwheel effect is caused by the way each star's dusty mantle is affected by that of its partner, producing spiral plumes.........
Posted by: Sean Permalink Source
Surprising Telescope Observations
CU-Boulder astrophysicist Jeffrey Linsky said new data gathered by NASA's Far Ultraviolet Spectroscopic Explorer, or FUSE, satellite, shows why deuterium appears to be distributed unevenly in the Milky Way Galaxy. It apparently has been binding to interstellar dust grains, changing from an easily detectable gaseous form to an unobservable solid form, said Linsky, a fellow of JILA, a joint institute of CU-Boulder and the National Institute of Standards and Technology.
The FUSE deuterium study, six years in the making, solves a 35-year-old mystery concerning the distribution of deuterium in the Milky Way while posing new questions about how stars and galaxies are made, as per the research team. A paper on the subject by a team of international scientists led by Linsky is being reported in the Aug. 20 issue of The Astrophysical Journal.
"Since the 1970s, we have been unable to explain why deuterium levels vary all over the place," said Linsky. "The answer we found is as unsettling as it is exciting".........
Posted by: Sean Permalink Source
Large and small stars in harmonious coexistence
This image reveals a large number of low-mass infant stars coexisting with young massive stars.........
Posted by: Sean Permalink Source
Hidden Milky Way deuterium found
This form of hydrogen, called deuterium, was created a few minutes after the Big.
Bang, but has been slowly destroyed as it is burned in stars and converted to heavier elements. In fact, it now turns out, that destruction has been occurring even more slowly than previously thought.
Reported in the Aug. 20 issue of the Astrophysical Journal, the FUSE team's new large deuterium survey solves a 35-year-old mystery concerning deuterium's uneven distribution in the Milky Way galaxy even as it poses new questions about how stars and galaxies are made.
"For more than three decades, we have struggled to understand and explain the widely varying levels of deuterium," said Warren Moos, principal investigator of NASA's.
FUSE mission and a professor in the Henry A. Rowland Department of Physics and Astronomy at the Krieger School of Arts and Sciences at Johns Hopkins. "Though the answer we have found may be unsettling to some, it represents a major step forward in our understanding of chemical evolution".........
Posted by: Sean Permalink Source
Electric Dust Storms on Mars
In 1976, the twin Viking landers scooped up Martian soil and added nutrients mixed with water to it. If microscopic life were present, the nutrients would be used up and waste products would be released. Three different experiments involved in this test gave conflicting results. The Labeled Release and the Gas Exchange experiments indicated something active was in the soil, because the nutrients were broken down. However, the Mass Spectrometer experiment did not find any organic matter in the soil.
In 1977, Viking researchers suggested that the contradiction could be explained if a very reactive nonorganic substance that imitated the activity of life by breaking down the nutrients was embedded in the soil. Hydrogen peroxide and ozone (O3) were considered possible reactive compounds.
While ultraviolet radiation from the sun could produce a certain amount of reactive chemicals in the atmosphere, nobody knew how large amounts of such reactive material could accumulate in the Martian soil. Some researchers at the time thought that dust storms might be electrically active like thunderstorms on Earth, and that these storms might be a source of the new reactive chemistry.........
Posted by: Sean Permalink Source
Atlantis Poised at the Pad
The STS-115 crew consists of Commander Brent W. Jett, Jr., Pilot Christopher J. Ferguson and Mission Specialists Heidemarie M. Stefanyshyn-Piper, Joseph R. Tanner, Daniel C. Burbank and Steven G. MacLean, who represents the Canadian Space Agency.
During their 11 days in space, the astronauts will install the integrated P3/P4 truss segment with its two large solar arrays that will provide one-fourth of the total power generation capability of the completed station.........
Posted by: Sean Permalink Source
15 Billion Kms And Counting
Voyager 1 is now heading away from the Sun at a speedy 17 km/s (38,250 mph) through the heliosheath and should pass beyond the heliopause - the point where the wind from the Sun is balanced by the wind from other stars which demarks interstellar space - within the next 10 years. The flight controllers expect that Voyager 1 (and Voyager 2) will still keep returning data up until 2020, so hopefully our first interstellar travellers will then be able to send back some interesting information about the heliopause.
For more information listen to a nice JPL podcast (13.3 MB).........
Posted by: Sean Permalink Source
Deeper Into Granicus And Tinjar Valles
Granicus Valles and Tinjar Valles
For high resolution images See this page
See these new images which are taken by the High Resolution Stereo Camera (HRSC) on board ESA's Mars Express spacecraft, show the regions of Granicus Valles and Tinjar Valles. It is believed that these regions may have been formed partly through the action of subsurface water, due to a process known as sapping.
The HRSC was able to obtained these images during orbit 1383 at a ground resolution of approximately 23.7 metres per pixel. These images have been rotated 90 degrees counter-clockwise, so that North would be directed to is to the left.
They show the regions of Granicus Valles and Tinjar Valles, lying at approximately 26.8 degree North and 135.7 degree East. The northwest-aligned Granicus Valles and Tinjar Valles are part of the Utopia-Planitia region, an area believed to be covered by a layer of lava that flowed from the northwest flanks of Elysium Mons into the Utopia-Planitia Basin.
Today, this once-smooth volcanic plain is incised by channels of variable size and appearance, including Granicus Valles (towards the West) and Tinjar Valles (towards the North).
Both channel systems evolve from a single main channel entering the image scene from southeast (upper right), exhibiting an approximate width of 3 km and extending 300 m below the surrounding terrain at maximum. The impressive sinuous lava channel emanates from the mouth of a radial, a circular drainage area, and runs to the Elysium rise trending into a graben, which is terrain dissected by tectonic deformation.........
Posted by: Sean Permalink Source
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