sexta-feira, 31 de outubro de 2008

Espectáculo celeste hoy al atardecer

Estimados amigos
Este dia 31 de Octubre en cuanto se oculte el sol preparence a ver un espectáculo celeste en donde los participantes principales son La Luna, Antares Venus (el mas brillante en éstos dias) y Júpiter.

Mapa celeste proporcionado porla NASA.

Esperando que lo disfruten

Su amigo de siempre
Fernando Cruz
Desde Cd. Sahagún, Hgo. México

quinta-feira, 30 de outubro de 2008

COROT sees sunquakes in other stars

Posted: October 24, 2008
The CNES/ESA Earth orbiting COROT satellite has applied the technique of seismology to the study of stellar interiors, probing the interiors of three stars beyond our own Sun for the first time.

COROT can detect 'starquakes', acoustic waves generated deep within a star that ripple across the star's surface, altering its brightness. By studying these variations, a star's mass, age and structure can be determined. Image: CNES.

Like the propagation of seismic waves on Earth providing information about our planet's interior, sound waves travelling throughout the Sun and other stars carry information about what is happening below the surface. The study of these waves propagating through a star is known as helioseismology, and has already been used to generate complex models of the interior conditions on our Sun, showing that different layers of our home star rotate at different speeds to generate the Sun's magnetic field, and that jet streams of plasma run thousands of kilometres below the surface.
Oscillations of the Sun's surface can also be tracked by direct observations and related to interior processes by the tool of helioseismology. Similar oscillations can be observed on other stars by watching for variations in the light emitted by the star as the surface wobbles, revealing both the internal structure of the star and the way energy is transported from the core to the surface.
"Other techniques to estimate stellar oscillations have been used from the ground, but they are limited in what they can do," says Malcolm Fridlund, ESA Project Scientist for COROT at ESA's European Space Research and Technology Centre (ESTEC). "Adverse weather conditions, plus the fact that you cannot observe stars during daytime, oblige ground astronomers to interrupt their observations."

COROT consists of a 27 centimetre telescope and was launched in December 2006. Image: CNES/D. Ducros.

The COROT satellite allows uninterrupted viewing from afar, and with high sensitivity instruments such as a 4-CCD camera capable of recording tiny variations of light intensity emitted from a star, COROT offers a new view of our stellar neighbourhood. In the new study, three Sun-like stars were scrutinized by COROT: HD499933, HD181420 and HD181906, revealing 'sunquakes' rumbling inside their interiors.
"The fact that COROT succeeded in probing the interior of Sun-like stars with direct measurements for the first time is a huge leap in understanding stars in general", says Fridlund. "In addition, this will help us to understand, by comparison, our own Sun even better."
COROT was launched at the end of 2006 and was designed as both a planet hunter and star surveyor, having clocked up six exoplanets to date with the aim of surveying around 120,000 stars for exoplanets, and over a hundred stars for stellar seismology studies.

Lucimary Vargas
Observatório Astronômico Monoceros
Além Paraíba-MG-Brasil

NASA orbiter reveals details of a wetter Mars

Posted: October 28, 2008
WASHINGTON -- NASA's Mars Reconnaissance Orbiter has observed a new category of minerals spread across large regions of Mars. This discovery suggests that liquid water remained on the planet's surface a billion years later than scientists believed, and it played an important role in shaping the planet's surface and possibly hosting life.

Credit: Credit: NASA/JPL-Caltech/Univ. of Arizona
Researchers examining data from the orbiter's Compact Reconnaissance Imaging Spectrometer for Mars have found evidence of hydrated silica, commonly known as opal. The hydrated, or water-containing, mineral deposits are telltale signs of where and when water was present on ancient Mars.

"This is an exciting discovery because it extends the time range for liquid water on Mars, and the places where it might have supported life," said Scott Murchie, the spectrometer's principal investigator at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "The identification of opaline silica tells us that water may have existed as recently as 2 billion years ago."

Until now, only two major groups of hydrated minerals, phyllosilicates and hydrated sulfates, had been observed by spacecraft orbiting Mars. Clay-like phyllosilicates formed more than 3.5 billion years ago where igneous rock came into long-term contact with water. During the next several hundred million years, until approximately 3 billion years ago, hydrated sulfates formed from the evaporation of salty and sometimes acidic water.

The newly discovered opaline silicates are the youngest of the three types of hydrated minerals. They formed where liquid water altered materials created by volcanic activity or meteorite impact on the Martian surface. One such location noted by scientists is the large Martian canyon system called Valles Marineris.

"We see numerous outcrops of opal-like minerals, commonly in thin layers extending for very long distances around the rim of Valles Marineris and sometimes within the canyon system itself," said Ralph Milliken of NASA's Jet Propulsion Laboratory in Pasadena, Calif.

Milliken is lead author of an article in the November issue of "Geology" that describes the identification of opaline silica. The study reveals that the minerals, which also were recently found in Gusev Crater by NASA's Mars rover Spirit, are widespread and occur in relatively young terrains.

In some locations, the orbiter's spectrometer observed opaline silica with iron sulfate minerals, either in or around dry river channels. This indicates the acidic water remained on the Martian surface for an extended period of time. Milliken and his colleagues believe that in these areas, low-temperature acidic water was involved in forming the opal. In areas where there is no clear evidence that the water was acidic, deposits may have formed under a wide range of conditions.

"What's important is that the longer liquid water existed on Mars, the longer the window during which Mars may have supported life," says Milliken. "The opaline silica deposits would be good places to explore to assess the potential for habitability on Mars, especially in these younger terrains."

The spectrometer collects 544 colors, or wavelengths, of reflected sunlight to detect minerals on the surface of Mars. Its highest resolution is about 20 times sharper than any previous look at the planet in near-infrared wavelengths.

NASA's Jet Propulsion Laboratory manages the Mars Reconnaissance Orbiter mission for NASA's Science Mission Directorate in Washington. Lockheed Martin Space Systems, Denver, is the prime contractor for the project and built the spacecraft. The Applied Physics Laboratory led the effort to build the spectrometer and operates the instrument in coordination with an international team of researchers from universities, government and the private sector.



Lucimary Vargas
Observatório Astronômico Monoceros
Além Paraíba-MG-Brasil

MESSENGER reveals more of Mercury's hidden territory

Scientists have now seen about 95 percent of the innermost planet.
Provided by NASA
This image of Mercury captured was by MESSENGER on the probe's second approach. NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington [View Larger Image]
October 29, 2008
A NASA spacecraft gliding over Mercury's battered surface for the second time this year revealed more previously unseen real estate on the innermost planet.

The probe also produced several science firsts and is returning hundreds of new photos and measurements of the planet's surface, atmosphere, and magnetic field.

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft flew by Mercury shortly after 4:40 A.M. EDT, October 6. It completed a critical gravity assist to keep it on course to orbit Mercury in 2011 and unveiled 30 percent of Mercury's surface never seen by a spacecraft.

"The region of Mercury's surface that we viewed at close range for the first time this month is bigger than the land area of South America," said Sean Solomon, principal investigator and director of the Department of Terrestrial Magnetism at the Carnegie Institution of Washington. "When combined with data from our first flyby and from Mariner 10, our latest coverage means that we have now seen about 95 percent of the planet."

The spacecraft's science instruments operated throughout the flyby. Cameras snapped more than 1,200 pictures of the surface, while the laser altimeter profiled the area's topography. The comparison of magnetosphere observations from the spacecraft's first flyby in January with data from the probe's second pass provids key new insight into Mercury's internal magnetic field and reveals new features of its magnetosphere. The magnetosphere is the volume surrounding Mercury that is controlled by the planet's magnetic field.

"The previous flybys by MESSENGER and Mariner 10 provided data only about Mercury's eastern hemisphere," said Brian Anderson of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland. "The most recent flyby gave us our first measurements on Mercury's western hemisphere, and with them, we discovered that the planet's magnetic field is highly symmetric."

The probe's Mercury Laser Altimeter (MLA), allowed scientists, for the first time, to correlate high-resolution topography measurements with high-resolution images.

"The MLA collected altimetry in regions where images from MESSENGER and Mariner 10 data are available, and new images were obtained of the region sampled by the altimeter in January," said Maria Zuber, co-investigator and head of the Department of Earth, Atmospheric, and Planetary Sciences at the Massachusetts Institute of Technology. "These topographic measurements now improve considerably the ability to interpret surface geology."

The Mercury Atmospheric and Surface Composition Spectrometer observed Mercury's thin atmosphere, known as an exosphere. The instrument searched for emissions from sodium, calcium, magnesium, and hydrogen atoms. Observations of magnesium are the first detection of this chemical in Mercury's exosphere. Preliminary analysis suggests the spatial distributions of sodium, calcium, and magnesium are different. Simultaneous observations of these spatial distributions, also a first for the spacecraft, have opened a window into the interaction of Mercury's surface and exosphere.

Spacecraft images reveal for the first time vast geologic differences on the surface.

"Now that MESSENGER's cameras have imaged more than 80 percent of Mercury, it is clear that, unlike the moon and Mars, Mercury's surface is more homogeneously ancient and heavily cratered, with large extents of younger volcanic plains lying within and between giant impact basins," said co-investigator Mark Robinson of Arizona State University in Tempe.

See's comprehensive coverage of MESSENGER's second flyby of Mercury.

Lucimary Vargas
Observatório Astronômico Monoceros
Além Paraíba-MG-Brasil

Solar system's young twin has two asteroid belts

Posted: October 27, 2008
Astronomers have discovered that the nearby star Epsilon Eridani has two rocky asteroid belts and an outer icy ring, making it a triple-ring system. The inner asteroid belt is a virtual twin of the belt in our solar system, while the outer asteroid belt holds 20 times more material. Moreover, the presence of these three rings of material implies that unseen planets confine and shape them.

This artist's conception shows the closest known planetary system to our own, called Epsilon Eridani. Credit: NASA/JPL-Caltech
The star Epsilon Eridani is slightly smaller and cooler than the Sun. It is located about 10.5 light-years from Earth in the constellation Eridanus. (A light-year is the distance light travels in one year, or about 6 trillion miles.) Epsilon Eridani is the ninth closest star to the Sun and is visible to the unaided eye. It is also younger than the Sun, with an approximate age of 850 million years.

Epsilon Eridani and its planetary system show remarkable similarities to our solar system at a comparable age.

"Studying Epsilon Eridani is like having a time machine to look at our solar system when it was young," said Smithsonian astronomer Massimo Marengo (Harvard-Smithsonian Center for Astrophysics). Marengo is a co-author of the discovery paper, which will appear in the Jan. 10 issue of The Astrophysical Journal.

Lead author Dana Backman (SETI Institute) agreed, saying, "This system probably looks a lot like ours did when life first took root on Earth."

Our solar system has a rocky asteroid belt between Mars and Jupiter, about 3 astronomical units from the Sun. (An astronomical unit equals the average Earth-Sun distance of 93 million miles.) In total, it contains about 1/20 the mass of Earth's Moon. Using NASA's Spitzer Space Telescope, the team of astronomers found an identical asteroid belt orbiting Epsilon Eridani at a similar distance of 3 astronomical units.

They also discovered a second asteroid belt 20 astronomical units from Epsilon Eridani (about where Uranus is located in our solar system). The second asteroid belt contains about as much mass as Earth's Moon.

A third, icy ring of material seen previously extends about 35 to 100 astronomical units from Epsilon Eridani. A similar icy reservoir in our solar system is called the Kuiper Belt. However, Epsilon Eridani's outer ring holds about 100 times more material than ours.

This artist's diagram compares the Epsilon Eridani system to our own solar system. The two systems are structured similarly, and both host asteroids (brown), comets (blue) and planets (white dots). Credit: NASA/JPL-Caltech
See larger image here
When the Sun was 850 million years old, theorists calculate that our Kuiper Belt looked about the same as that of Epsilon Eridani. Since then, much of the Kuiper Belt material was swept away, some hurled out of the solar system and some sent plunging into the inner planets in an event called the Late Heavy Bombardment. (The Moon shows evidence of the Late Heavy Bombardment - giant craters that formed the lunar seas of lava called mare.) It is possible that Epsilon Eridani will undergo a similar dramatic clearing in the future.

"Epsilon Eridani looks a lot like the young solar system, so it's conceivable that it will evolve similarly," said Marengo.

The Spitzer data show gaps between each of the three rings surrounding Epsilon Eridani. Such gaps are best explained by the presence of planets that gravitationally mold the rings, just as the moons of Saturn constrain its rings.

"Planets are the easiest way to explain what we're seeing," stated Marengo.

Specifically, three planets with masses between those of Neptune and Jupiter would fit the observations nicely. A candidate planet near the innermost ring already has been detected by radial velocity studies. Those studies suggested that it orbited Epsilon Eridani on a highly elliptical path, characterized by an eccentricity of 0.7. The new finding rules out such an orbit, because the planet would have cleared out the inner asteroid belt long ago through gravitational disruption.

A second planet must lurk near the second asteroid belt, and a third at about 35 astronomical units near the inner edge of Epsilon Eridani's Kuiper Belt. Future studies may detect these currently unseen worlds, as well as any terrestrial planets that may orbit inside the innermost asteroid belt.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.


Lucimary Vargas
Observatório Astronômico Monoceros
Além Paraíba-MG-Brasil

Cosmic lens reveals distant galactic violence

Astronomers gained a rare glimpse of the violent assembly of a young galaxy.
Provided by NRAO, Socorro, New Mexico
Cosmic lens
Imaging a distant galaxy using a gravitational lens. Bill Saxton/NRAO/AUI/NSF [View Larger Image]
October 21, 2008
By cleverly unraveling the workings of a natural cosmic lens, astronomers have gained a rare glimpse of the violent assembly of a young galaxy in the early universe. Their new picture suggests that the galaxy has collided with another, feeding a super-massive black hole and triggering a tremendous burst of star formation.

The astronomers used the National Science Foundation's Very Large Array (VLA) radio telescope in Socorro, New Mexico, to look at a galaxy more than 12 billion light-years from Earth, seen as it was when the universe was only about 15 percent of its current age. Between this galaxy and Earth, lies another distant galaxy so perfectly aligned along the line of sight that its gravity bends the light and radio waves from the farther object into a circle, or "Einstein Ring."

This gravitational lens made it possible for the scientists to learn details of the young, distant galaxy that would have been unobtainable otherwise.

"Nature provided us with a magnifying glass to peer into the workings of a nascent galaxy, providing an exciting look at the violent, messy process of building galaxies in the early history of the universe," said Dominik Riechers, who led this project at the Max Planck Institute for Astronomy in Germany and now is a Hubble Fellow at the California Institute of Technology (Caltech) in Pasadena.

The new picture of the distant galaxy, dubbed PSS J2322+1944, shows a massive reservoir of gas, 16,000 light-years in diameter, that contains the raw material for building new stars. A super-massive black hole is voraciously eating material, and new stars are being born at the rate of nearly 700 suns per year. By comparison, our Milky Way Galaxy produces the equivalent of about three to four suns per year.

The black hole appears to be near the edge, rather than at the center, of the giant gas reservoir. Astronomers say this location indicates the galaxy has merged with another.

"This whole picture of massive galaxies and super-massive black holes assembling themselves through major galaxy mergers so early in the universe is a new paradigm in galaxy formation. This gravitationally lensed system allows us to see this process in unprecedented detail," Chris Carilli of the National Radio Astronomy Observatory in Charlottesville, Virginia, said.

In 2003, astronomers studied PSS J2322+1944 and found the Einstein Ring by observing carbon monoxide (CO) molecules emit radio waves. When astronomers see large amounts of CO in a galaxy, they conclude that there also is a large amount of molecular hydrogen present, and thus a large reservoir of fuel for star formation.

In the latest study, scientists painstakingly produced a physical model of the lensing intermediate galaxy. By knowing the galaxy's mass, structure, and orientation, they deduced the details of how it bends light and radio waves from the more-distant galaxy. Then they reconstructed a picture of the distant object. By doing multiple VLA images made at different radio frequencies helped the team measure the motions of the gas in the distant galaxy.

"The lensing galaxy was, in effect, part of our telescope. By projecting backward through the lens, we determined the structure and dynamics of the galaxy behind it," Fabian Walter said of the Max-Planck Institute for Astronomy in Germany.

George Djorgovski of Caltech used the digitized Palomar Observatory Sky Survey to discover PSS J2322+1944. Later radio and optical studies showed it had a huge reservoir of dust and molecular gas and indicated gravitational lensing.

Albert Einstein's General Theory of Relativity predicted gravitational lenses in 1919. In 1936, Einstein showed that a perfectly aligned gravitational lens would produce a circular image, but he felt the chances of actually observing such an object were nearly zero. The first gravitational lens was discovered in 1979, and researchers using the VLA in 1987 discovered the first Einstein Ring.

MESSENGER unveils more 'hidden' territory on Mercury

Posted: October 29, 2008

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Gliding over the battered surface of Mercury for the second time this year, NASA's MESSENGER spacecraft has revealed even more previously unseen real estate on the innermost planet, sending home hundreds of photos and measurements of its surface, atmosphere, and magnetic field.

The probe flew by Mercury shortly after 4:40 a.m. EDT on October 6, 2008, completing a critical gravity assist to keep it on course to orbit Mercury in 2011 and unveiling 30 percent of Mercury's surface never before seen by spacecraft.

"The region of Mercury's surface that we viewed at close range for the first time this month is bigger than the land area of South America," says Sean Solomon, MESSENGER principal investigator and the director of the Department of Terrestrial Magnetism at the Carnegie Institution of Washington. "When combined with data from our first flyby and from Mariner 10, our latest coverage means that we have now seen about 95% of the planet."

MESSENGER's science instruments worked feverishly through the flyby - cameras snapped more than 1,200 pictures of the surface, while topography beneath the spacecraft was profiled with the laser altimeter. "We have completed an initial reconnaissance of the solar system's innermost planet, enabling us to gain a global view of Mercury's geological history and internal magnetic field geometry for the first time," Solomon continues.

The comparison of magnetosphere observations from MESSENGER's first flyby in January with data from the probe's second pass has provided key new insight into the nature of the planet's internal magnetic field and revealed new features of Mercury's magnetosphere.

"The previous flybys by MESSENGER and Mariner 10 provided data only on Mercury's eastern hemisphere," explains Brian Anderson, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. "The most recent flyby gave us our first measurements on Mercury's western hemisphere, and with them we discovered that the planet's magnetic field is highly symmetric."

"This seemingly simple result is significant for the planet's internal field because it implies that the dipole is even more closely aligned with the planet's rotation axis than we could conclude before the second flyby," says Anderson, who is deputy project scientist. "Even though the rigorous analyses of these data are ongoing, we expect that this result will allow us to limit the theories of planetary magnetic field generation to those that predict a strongly rotationally aligned moment."

The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) observed the extended tail, night side, and day side regions of Mercury's thin atmosphere - known as an exosphere - searching for emission from sodium, calcium, magnesium, and hydrogen atoms.

"The MASCS observations of magnesium are the first-ever detection of this species in Mercury's exosphere," explains MESSENGER participating scientist Ron Vervack of APL. Preliminary analysis of the sodium, calcium, and magnesium observations suggests that the spatial distributions of these three species are different and that the distribution of sodium during the second flyby is noticeably different from that observed during the first flyby.

"The spatial distributions of sodium, calcium, and magnesium are a reflection of the processes that release these species from Mercury's surface," Vervack adds. "Now that we were finally able to measure them simultaneously, we have an unprecedented window into the interaction of Mercury's surface and exosphere."

The probe's Mercury Laser Altimeter (MLA) measured the planet's topography, allowing scientists, for the first time, to correlate high-resolution topography measurements with high-resolution images.

"During the last flyby, the Mercury Laser Altimeter acquired a topographic profile in a hemisphere of the planet for which there were no spacecraft images," explains Maria Zuber, MESSENGER co-investigator and head of the Department of Earth, Atmospheric, and Planetary Sciences at the Massachusetts Institute of Technology. "During the second flyby, in contrast, altimetry was collected in regions where images from MESSENGER and Mariner 10 are available, and new images were obtained of the region sampled by the altimeter in January. These topographic measurements now improve considerably the ability to interpret surface geology."

Now that MESSENGER's cameras have imaged more than 80 percent of Mercury, it is clear that, unlike the Moon and Mars, the planet lacks hemispheric-scale geologic differences. "On the Moon, dark volcanic plains are concentrated on the near side and are nearly absent from the far side," says MESSENGER co-investigator Mark Robinson of Arizona State University. "On Mars, the southern hemisphere consists of older, cratered highlands, whereas the northern hemisphere consists of younger lowlands. Mercury's surface is more homogeneously ancient and heavily cratered, with large extents of younger volcanic plains lying within and between giant impact basins."

Color imaging also shows that Mercury's crust is compositionally heterogeneous. "Although definitive compositional interpretations cannot yet be made, the distribution of different components varies both across the surface and with depth - Mercury's crust is more analogous to a marbled cake than a layered cake," Robinson adds. "Once MESSENGER's suite of science instruments returns a host of data from the orbital phase of the mission, compositions will be determined for the newly discovered color units."

"The first two Mercury flybys have returned a rich dividend of new observations," says Solomon. "But some of the observations we are most eager to make - such as the chemical make-up of Mercury's surface and the nature of its enigmatic polar deposits - will not be possible until MESSENGER begins to orbit the innermost planet. Moreover, the very dynamic nature of Mercury's interaction with its interplanetary environment has taught us that continuous observations will be required before we can claim to understand our most sunward sister planet."

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. The MESSENGER spacecraft launched on August 3, 2004, and after flybys of Earth, Venus, and Mercury will start a yearlong study of its target planet in March 2011. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as principal investigator. The Johns Hopkins University Applied Physics Laboratory  built and operates the MESSENGER spacecraft and manages this Discovery-class mission for NASA.

The Applied Physics Laboratory, a division of the Johns Hopkins University, meets critical national challenges through the innovative application of science and technology.


Lucimary Vargas
Observatório Astronômico Monoceros
Além Paraíba-MG-Brasil

Fireball captured by Canadian cameras

Posted: October 28, 2008For the second time this year The University of Western Ontario's Meteor Group has captured rare footage of a meteor streaking across the sky and possibly falling to the ground.
The meteor was tracked by all seven of Western's Southern Ontario Meteor Network cameras at 5:28 am on Wednesday 15 October, local time. Western University astronomers suspect that some fraction of the meteor may have fallen to the ground, amounting to a few hundred grams in mass.

All seven cameras of the Meteor Network spotted this meteor streaking across the sky; this image was taken by the Orangeville camera number 6. The lights at the bottom are a moving aircraft. Video of the meteor is available here. Image: University of Western Ontario.

By studying the video footage, the astronomers concluded that the meteor penetrated the Earth's atmosphere at an altitude of around 37 kilometres whereupon it slowed down considerably. Most meteoroids burn up by the time they hit an altitude of 60-70 kilometres from the ground, but in this case, one or more small meteorites could have made it to the ground intact. The surviving fragments are predicted to lie in a region north of Guelph. The trajectory of the meteor could also be tracked back to its pre-impact orbit, putting it into the typical Earth crossing asteroid type of a stony meteorite. Stony meteorites are composed mostly of silicate minerals and account for around 95 percent of all meteorites seen to fall to Earth.
In March, the same network of all-sky cameras captured a meteor careering towards the Parry Sound area. All-sky cameras consist of a fish eye lens that enables the whole sky to be imaged at once, as the name suggests. A network of three or more cameras allows the meteors to be located via triangulation.

The fireball is suspected to have shed meteorites in a region north of Guelph. Residents are encouraged to contact researchers at Western if they witnessed the event or if they have found fragments of the meteorite. Image: University of Western Ontario.

Just a week before the Canadian accomplishment, a three-metre wide asteroid was seen powering through the skies of northern Sudan as a glowing fireball (read our report here). Meteors streak across the sky on a daily basis, and when the Earth passes through the tail of a comet, we are treated to a meteor shower, such as the Perseids, Orionids, Leonids and Geminids, which offer the best displays. However, it is quite rare that meteoritic material reaches the ground intact, but finding this treasure allows scientists to sample the material of an extraterrestrial body, teaching us about the composition of the residents of our cosmic neighbourhood. The three-metre wide asteroid was a reminder that the Earth is also at risk from potentially devasting impacts without much notice, indeed, that case study was detected less than a day before it was due to penetrate the Earth's atmosphere.

Lucimary Vargas
Observatório Astronômico Monoceros
Além Paraíba-MG-Brasil

Rare event in life of distant quasar revealed

Posted: October 29, 2008
GAINESVILLE, Fla. - A bit of serendipity has given astronomers a surprise view of a never-before-observed event in the birth of a galaxy.

University of Florida and University of California-Santa Cruz astronomers are the first to discover the onset of a huge flow of gas from a quasar, or the super-bright core of an extremely remote young galaxy still being formed. The gas was expelled from the quasar and its enormous black hole sometime in the space of four years around 10 billion years ago - an extremely brief and ancient blip noticed only by a sharp-eyed undergraduate and the unlikely convergence of two separate observational efforts.

In this artist's depiction, the outflow of blue gas surrounds the black hole in the quasar. Credit: (University of Florida/Myda Iamiceli
"It was completely serendipitous," said Fred Hamann, a UF astronomy professor. "In fact, the only way it could have happened is through serendipity."

A paper about the research appeared online this month in the Letters of the Monthly Notices of the Royal Astronomical Society.

Quasars are enormously bright cores of very distant galaxies thought to contain "super-massive" black holes a billion times larger than our sun. They are seen only in the centers of very distant galaxies that formed long ago - galaxies whose light is just now reaching Earth after billions of years in transit. The quasar in question occurred about 10.3 billion years ago.

The black holes within quasars are invisible, but the cosmic material cascading toward them builds up and forms hot "accretion" disks, the source of quasars' intense light. Some of the incoming material also can be expelled from quasars to form enormous gas clouds that zoom out at extremely high speeds. With the quasar in question, the gas is flowing at an astonishing rate of 58 million mph, Hamann said.

But while astronomers had observed the presence of such gas clouds with other quasars, they had never witnessed one actually coming into being - until now.

Hamann said the discovery was initiated when Kyle Kaplan, an undergraduate at UC-Santa Cruz, earlier this spring noticed peculiarities in the spectra, or wavelengths of light, that had been observed and recorded from the quasar. The spectra were gathered in 2006 as part of an effort to study the galaxies between the quasar and Earth.

UC-Santa Cruz Professor Jason Prochaska was aware of Hamann's work on quasars and asked him to take a look.

When Hamann and other astronomers checked the spectra against the spectra of the same region recorded in a separate sky survey in 2002, they were surprised to discover that there were zero indications of the gas cloud.

"So that's how we know this appeared between 2002 and 2006," he said.

Daniel Progra, a physics professor at the University of Nevada, Las Vegas and an expert on gas outflows from astronomical objects, indicated the discovery is a lucky one.

"I am most excited about this work," he said. "We humans cannot directly monitor changes in quasars as they take very many years. Therefore, a discovery of a change over a few years is very interesting. It is not unexpected, but chances are very small."

He said the discovery supports a computer model he developed that predicts the gas outflows are dynamic and complicated.

Hamann said the discovery also opens a window to understanding more about how quasars come into being.

"The fact that we saw one appear in so short a time frame means that it's a volatile type of structure," he said. "It could be an evolutionary phase, or maybe a transition stage from one phase to another."

It also poses interesting questions about the role of quasars in the formation of galaxies. Astronomers hope future observations will prove telling, Hamann said.

"One interesting question in astronomy is Œhow does the evolution of quasars relate to the evolution of galaxies?,'" he said. "The matter ejected from quasars might be the key to this relationship because it can disrupt or regulate the formation of galaxies around quasars. This discovery is a small piece of that story that we can see happening in real time, and what we are going to do now is keep watching."

Other astronomers and authors of the paper are Paola Rodriquez Hidalgo, a UF graduate student, and Stephane Herbert-Fort, a University of Arizona graduate student.

Lucimary Vargas
Observatório Astronômico Monoceros
Além Paraíba-MG-Brasil

Sonda vê "terremoto" de alto impacto em estrelas


da Folha de S.Paulo

Prever o comportamento de uma pessoa sem conhecê-la por dentro é impossível. Portanto, os dados enviados pelo telescópio Corot, que está a uma altura de 897 quilômetros da Terra, estão sendo comemorado pelos físicos e astrônomos. Pela primeira vez, a ciência tem dados das entranhas de estrelas mais quentes e com mais massa do que o Sol, e mostra que elas também sofrem "terremotos" internos.
O termo correto, na verdade é "estelemoto" --a palavra terremoto é aplicável apenas a estruturas sólidas e o interior das estrelas estudadas apresenta apenas plasma. Em estudo na revista "Science", os cientistas descrevem agora esses tremores em três objetos que estão de 100 a 200 anos-luz de distância da Terra, e que foram observados por pelo menos 60 dias.

"Chega a ser absolutamente surpreendente", afirma à Folha o físico José Renan de Medeiros, da UFRN (Universidade Federal do Rio Grande do Norte).
Segundo o pesquisador, um dos brasileiros que participam do Projeto Corot, de origem européia, as oscilações (os estelemotos) medidas nas três estrelas são 1,5 vezes maiores do que as registradas no Sol.
Os cálculos são feitos a partir da variação de luminosidade provocada pela retração e expansão do interior das estrelas e captadas pelo Corot --o telescópio lançado no fim de 2006 tem 27 cm de diâmetro.
"Esses dados mostram que nós temos que ir mesmo ao espaço se quisermos avançar na compreensão da emissão solar", diz.
Segundo Medeiros, o estudo, assim como toda a missão Corot, é uma grande oportunidade que existe para desvendar a história evolutiva do Sol, pois conhecer as estrelas por dentro ajuda a revelá-las por fora.
Plasma em borbulhas
A chamada granulação das estrelas --grosso modo, a quantidade de borbulhas que existe no plasma na superfície do corpo celeste-- é outra medida pioneira da Corot. "Esse dado é importante porque a granulação reflete o quanto movimentos convectivos no interior da estrela [a subida do plasma mais quente] são importantes. Isso, ao ser casado com a rotação da estrela, indica sua atividade magnética", diz Medeiros.
Com esse primeiro resultado, um dos objetivos do projeto começa a ser cumprido, explica o cientista da UFRN --em Natal há uma central que recebe dados da Corot. O estudo ajuda a entender o interior das estrelas e, por tabela, o do Sol. Este último, os cientistas já conheciam, mas não sabiam se ele era similar ao de outras estrelas.
A segunda parte da missão, diz Medeiros, também é promissora. "Estamos desenvolvendo uma técnica estatística que será uma ferramenta primordial para que se encontre centenas ou, porque não, milhares de planetas [fora do Sistema Solar] do dia para a noite."

Vénus, um planeta simples?


Imagem de Vénus produzida por computador Crédito: NASA
Foi recentemente apresentado o primeiro mapa geológico global de Vénus
É o segundo planeta mais próximo do Sol. Em termos de dimensões e massa é muito semelhante à Terra. A sua caracteristica mais marcante é possuir uma atmosfera de CO2 muito densa e um efeito de estufa muito intenso. Elaborado pelo cientista russo M. Ivanov, O estudo das imagens (de radar) disponíveis, bem como das regiões já mapeadas, permitiu o reconhecimento de 11 unidades (ou tipos de terreno) e a conclusão de que essas poucas unidades cobriam toda a superfície do segundo planeta
Um planeta é um objecto que se forma no disco que circunda uma estrela em formação e cuja massa é superior à de Plutão (1/500 da massa da Terra) e inferior a 10 vezes a massa de Júpiter. Ao contrário das estrelas, os planetas não produzem luz, apenas reflectem a luz da estrela que orbitam.
Sistema Solar
O Sistema Solar é constituído pelo Sol e por todos os objectos que lhe estão gravitacionalmente ligados: planetas e suas luas, asteróides, cometas, material interplanetário.
Dito desta forma, parece que a geologia de Vénus é bastante simples… Mas esta simplicidade é enganadora, e traduz de facto um assombroso mistério: o que se passou em Vénus? Há poucas crateras de impacto
cratera de impacto
As crateras de impacto são depressões circulares resultantes de colisões entre corpos pequenos (por exemplo cometas, asteróides ou meteoritos) e a superfície de corpos celestes maiores, tais como planetas ou satélites naturais. As crateras de impacto possuem geralmente um bordo levantado, formado pelo material ejectado aquando da colisão, o que se explica pela densa atmosfera
1- Camada gasosa que envolva um planeta ou uma estrela. No caso das estrelas, entende-se por atmosfera as suas camadas mais exteriores. 2- A atmosfera (atm) é uma unidade de pressão equivalente a 101 325 Pa., capaz de "derreter" a maior parte dos bólides que nela penetram, e a sua distribuição indica que a actual superfície do planeta é (em termos geológicos e astronómicos) relativamente jovem. Não temos dados que nos indiquem qual seria o aspecto do planeta há mais de 1 milhar de milhões de anos atrás. Até na Terra, com toda a sua dinâmica e constante renovação da superfície, existem, espalhadas pelo planeta, pequenas peças rochosas do puzzle de tempos mais remotos. Terá Vénus sido vítima de um verdadeiro cataclismo vulcânico, com uma explosão de erupções há centenas de milhões de anos atrás, capaz de refazer quase toda a superfície num curto período? O certo é que os vulcões que ainda hoje observamos em Vénus parecem estar adormecidos, quiçá moribundos, gastos… Ainda não se detectou nenhuma erupção a ocorrer no planeta. Que, recordamos, tem aproximadamente as mesmas dimensões que o nosso – mas uma história muito diferente. E definitivamente nada simples.


© NUCLIO - Núcleo Interactivo de Astronomia 2001-2006


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O Dia em Que o Mundo Não Acabou

O mundo não acabou. Ligar o maior e mais poderoso acelerador de partículas do mundo próximo a Genebra, Suiça, não disparou a criação de um buraco negro microscópico. E este buraco negro não começou rapidamente a sugar a matéria ao redor cada vez mais rápido até que devorou por completo a Terra, como jornalistas sensacionalistas sugeriram que poderia acontecer.

É claro que você já sabia disto, afinal você está vivo e lendo este artigo hoje. Atualmente o acelerador, um anel subterrâneo com cerca de 7,5 quilômetros chamado de Grande Colisor de Hádrons (Large Hadron Collider - LHC em inglês), foi desligado para reparos. Mas na hora em que esta máquina poderosíssima for religada, há alguma chance deste cenário do dia do juízo final ainda acontecer?

Relaxe. Como diria Mark Twain, relatos sobre a morte da Terra são sempre exagerados.

"Realmente nunca houve perigo vindo do acelerador, mas isto não impediu que as pessoas especulassem que poderia haver!" disse Robert Johnson, físico do Instituto Santa Cruz de Física das Partículas e membro da equipe científica do Telescópio Espacial de Raios Gama Fermi da NASA, que foi lançado em Junho para estudar raios gama de vários fenômenos, inclusive de possíveis buracos negros evaporando.

Existem vários motivos pelos quais o mundo não acabou em 10 de setembro, e porque o Grande Colisor de Hádrons não é capaz de iniciar esta calamidade.

Em primeiro lugar, sim, é verdade que o LHC pode criar microscópicos buracos negros. Mas, para registro, ele não poderia tê-los criado no seu primeiro dia. Isto porque os cientistas no CERN não puseram em rota de impacto os feixes de prótons para assim criar colisões de alta energia. O dia 10 de setembro foi apenas um pequeno aquecimento. Até agora, o colisor ainda não produziu qualquer colisão, e é a energia extrema destas colisões - até 14 tera-elétron Volts - que potencialmente poderia criar um microscópico buraco negro.

Na realidade, assim que o LHC voltar a funcionar e começar a produzir colisões, os cientistas ficarão emocionados se ele criar um pequeno buraco negro. Isto seria a primeira evidência experimental a suportar uma elegante mas não provada e controversa "teoria do tudo" chamada teoria das cordas.

Na teoria das cordas, elétrons, prótons, quarks, e todas as outras partículas fundamentais são diferentes vibrações de cordas infinitesimais de 10 dimensões: 9 dimensões espaciais e uma dimensão temporal. (As outras 6 dimensões espaciais estão escondidas por uma explicação ou outra, por exemplo por ser "embrulhada" em uma escala extremamente pequena.) Alguns cientistas exaltam a elegância matemática da teoria das cordas e sua habilidade em integrar a gravidade com outras forças da natureza. O geralmente aceito Modelo Padrão da física das partículas não inclui a gravidade, que é uma das razões dele não predizer que o LHC poderia criar um ponto gravitacionalmente colapsado - um buraco negro - enquanto a teoria das cordas o prediz.

Muitos cientistas começaram a ter dúvida se a teoria das cordas é verdadeira. Mas assumindo por um instante que ela seja, o que aconteceria quando um buraco negro nascesse dentro do LHC? A supreendente resposta é "quase nada." Mesmo que o buraco negro sobrevivesse por mais que uma fração de segundo (o que provavelmente não aconteceria), muito provavelmente ele seria arremessado no espaço. "Ele teria somente a massa de uma centena ou mais de prótons, e estaria se movendo próximo à velocidade do som, assim facilmente ele teria facilmente a velocidade de escape," explica Johnson. Já que o minúsculo buraco negro seria menor que um milionésimo do tamanho de um próton e teria um empuxo gravitacional extremamente fraco, ele poderia facilmente atravessar a rocha sólida sem sequer tocá-la - ou absorver - qualquer matéria. Do ponto de vista de algo tão minúsculo, os átomos que formam a rocha "sólida" parecem ser quase como um espaço inteiramente vazio: o enorme espaço entre o núcleo do átomo e seus elétrons. Assim, um micro buraco negro poderia mergulhar em direção ao centro da Terra e sair do outro lado sem causar nenhum dano. De qualquer maneira, ele acabaria no quase vácuo do espaço, onde a chance de tocar ou absorver qualquer matéria para se tornar uma ameaça crescente seria menor ainda.

Assim, a primeira coisa que um micro buraco negro faria era deixar para trás o planeta de forma segura. Mas existem outras razões ainda mais fortes pelas quais os cientistas acreditam que o LHC não ameaça de forma alguma a Terra. Uma delas é que um buraco negro criado no LHC quase que certamente evaporaria antes que fosse muito longe, acreditam quase todos os cientistas. Stephen Hawking, o físico que escreveu a Uma Breve História do Tempo, previu que buracos negros irradiam energia, um fenômeno conhecido como radiação de Hawking. Devido a sua perda de energia constante, o buraco negro finalmente evaporaria. Quanto menor for o buraco negro, mais intensa será a radiação Hawking, e mais rápido o buraco negro desaparecerá. Desta forma, um buraco negro milhares de vezes menor que um próton deveria desaparecer quase instantaneamente em uma rápida descarga de energia.

"A previsão de Hawking não é baseada na especulativa teoria das cordas mas sim em princípios bem conhecidos da mecânica quântica e da física das partículas," observa Johnson.

Apesar de sua forte fundamentação teórica, a radiação de Hawking nunca foi observada diretamente. Ainda assim, os cientistas estão confiantes que qualquer buraco negro criado pelo LHC não representa qualquer ameaça. Como eles podem estar tão certos? Istro deve-se aos raios cósmicos. Milhares de vezes por dia, raios cósmicos de alta energia atingem a atmosfera da Terra, colidindo com moléculas no ar com 20 vezes mais energia que a mais poderosa colisão que poderá ser criada pelo LHC. Assim, se este acelerador pudesse criar buracos negros devoradores da Terra, os raios cósmicos já o teriam feito bilhões de vezes ao longo da história da Terra.

Então, já que estamos aqui. Que comecem as colisões!!!


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Oscilações universais

Oscilações universais
Com dados do satélite Corot, cientistas detectam, em estrelas fora do Sistema Solar, fenômenos de oscilação e granulação semelhantes aos que ocorrem no Sol. Descoberta, com participação brasileira, ajudará a conhecer mais sobre a evolução da galáxia (divulgação)
Por Fábio de Castro
Agência FAPESP – A partir de dados obtidos pelo satélite francês Corot, um grupo internacional de cientistas mediu pela primeira vez vibrações físicas e características de superfície de três estrelas próximas. Até agora, as oscilações solares – cuja descoberta possibilitou os atuais estudos sobre a estrutura do interior do Sol – ainda não haviam sido medidas em outras estrelas.
Os resultados do estudo, que teve participação brasileira, foram publicados em matéria de capa da edição desta sexta-feira (24/10) da revista Science. De acordo com os autores, as três estrelas observadas apresentaram oscilações 1,5 vez mais fortes que a do Sol e granulação três vezes mais fina. Os dados, que só puderam ser obtidos graças à alta sensibilidade do satélite, deverão gerar avanços no conhecimento sobre a evolução da galáxia.
Dois astrônomos brasileiros estão entre os autores do artigo: José Renan de Medeiros, professor titular do Departamento de Física Teórica e Experimental da Universidade Federal do Rio Grande do Norte (UFRN), e Eduardo Janot Pacheco, do Instituto de Astronomia, Geofísica e Ciências Atmosféricas da Universidade de São Paulo (IAG-USP), que coordena a participação brasileira no projeto.
A missão do Corot, lançado em 2006, tem duas vertentes principais: localizar, fora do Sistema Solar, planetas com condições semelhantes às da Terra que possam abrigar vida, e estudar a estrutura e a evolução das estrelas – isto é, a sismologia estelar. De acordo com Medeiros, esses são os primeiros resultados nessa segunda vertente.
"A equipe brasileira está particularmente presente nos trabalhos voltados para a sismologia estelar. Nossa atividade consiste principalmente no tratamento e interpretação de dados. Durante a fase de observação das estrelas pelo Corot, utilizamos grandes telescópios terrestres para caracterizar as estrelas – ou seja, estabelecer seus parâmetros físicos e químicos", disse Medeiros à Agência FAPESP.
Segundo ele, as oscilações, produzidas pelo movimento do plasma que constitui o interior estelar, só haviam sido observadas até agora no Sol. Pela primeira vez foram medidas em estrelas mais quentes e mais antigas.
"As estrelas se comportam como instrumentos musicais, que produzem e propagam ondas ressonantes. Essas ondas provocam alterações periódicas de diversas propriedades que caracterizam a estrela. Assim como os sons emitidos por um instrumento dependem das características da cavidade na qual as ondas sonoras se propagam, as 'notas' emitidas pela estrela, que são seus modos próprios de oscilação, estão relacionadas ao seu interior. As oscilações refletem o que se passa além da superfície estelar", explicou.
Além das oscilações, foram detectadas as granulações da superfície das três estrelas – um fenômeno também até agora conhecido apenas no Sol. A granulação, de acordo com Medeiros, é um reflexo dos movimentos convectivos no interior do plasma solar que também fornece pistas sobre a natureza do campo magnético da estrela e sobre o comportamento de seu interior.
A fotosfera solar apresenta grânulos brilhantes rodeados por contornos mais escuros, com cerca de 700 quilômetros de diâmetro. A granulação solar é formada no topo da zona convectiva, região em que as massas de gás quente conhecidas como células de convecção crescem e transportam a energia que será dissipada na fotosfera. Com o esfriamento, os gases voltam a descer para o interior solar.

Grande precisão

De acordo com o professor da UFRN, os resultados representam um marco para a sismologia estelar, mas são apenas as primeiras descobertas de uma série.
"A filosofia de uma missão como a do Corot é descrever a história evolutiva das estrelas. Para isso, queremos observá-las em diferentes fases. Essas três estrelas são mais quentes e antigas do que o Sol, mas vamos observar também estrelas mais jovens e muito mais velhas. Isso nos dará elementos para fazer inferências sobre a história evolutiva do Sol", afirmou.
Um dos principais aspectos do estudo é que ele aponta para a universalidade dos fenômenos físicos já observados no Sol. "Isso por si só é um grande passo, porque, quando se desenvolvem teorias, é preciso ter o que chamamos de condições iniciais ou condições de contorno. Estamos conseguindo essas condições a partir de medidas feitas com precisão inédita. Isso tornará as futuras teorias muito mais consistentes", disse Medeiros.
Os resultados serviram também para confirmar a extrema precisão do Corot. "Os dados utilizados nesse estudo foram obtidos nos primeiros 150 dias de observação do satélite. Os resultados tiveram tanto impacto que a coordenação global da missão resolveu ampliar as observações, que seriam inicialmente de 18 meses, para 36 meses", contou.
O método utilizado para a obtenção dos dados, segundo Medeiros, baseia-se na técnica da fotometria estelar. "O telescópio observa a estrela e registra as flutuações na luminosidade da sua superfície. Como ele tem uma performance notável, pode detectar uma variabilidade luminosa da ordem de dez elevado a menos cinco. Com isso, podemos concluir se o fenômeno observado é de granulação ou oscilação", disse.
No caso das três estrelas, foram feitas medidas ininterruptas durante vários meses. "Isso criou condições para termos informações com um detalhamento sem precedentes", afirmou. A estrela HD49933 foi observada por 60 dias seguidos. As estrelas HD181420 e HD181906 foram observadas por 156 dias cada uma, ininterruptamente.
O artigo Corot measures solar-like oscillations and granulation in stars hotter than the Sun, de Eric Michel e outros, pode ser lido por assinantes da Science em

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Fabricação de naves Soyuz corre risco por falta de financiamento

da Efe, em Moscou
A fabricação das naves tripuladas Soyuz pode ser afetada por falta de financiamento, informou nesta sexta-feira Vitali Lapota, diretor da corporação russa especializada na produção de aparelhos espaciais.
"Se nas próximas duas ou três semanas não recebermos adiantamentos ou créditos não poderemos assumir a responsabilidade pela fabricação das Soyuz", disse em entrevista coletiva no Centro de Controle de Vôos Espaciais (CCVE) da Rússia, nos arredores de Moscou.
O funcionário explicou que dois terços dos recursos usados para a fabricação das Soyuz se originam em créditos e até agora sua corporação não recebeu os fundos necessários.
Lapota afirmou que isso se deve ao fato de o governo não ter ditado ainda a resolução para a concessão dos empréstimos e à crise financeira mundial.
"Não recebemos os créditos e não temos esperanças de que os bancos serão condescendentes conosco", disse.
As naves Soyuz serão o único veículo de abastecimento e revezamento de tripulações da ISS (Estação Espacial Internacional, na sigla em inglês).

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Dez anos em órbita

Dez anos em órbita
Satélite SCD-2, segundo satélite projetado, construído e operado por brasileiros, está em operação desde 1998 (divulgação)
Agência FAPESP – O SCD-2, segundo satélite de coleta de dados ambientais desenvolvido pelo Instituto Nacional de Pesquisas Espaciais (Inpe), está completando dez anos em plena operação. O SCD-2 foi lançado em 22 de outubro de 1998 pelo foguete americano Pegasus, o mesmo que colocou em órbita o SCD-1 em fevereiro de 1993, também ainda operacional.
Os primeiros satélites projetados, construídos e operados por brasileiros continuam apresentando desempenho satisfatório, embora tenham sido projetados para uma vida útil de até dois anos. Segundo o Inpe, a longevidade é resultado da competência tecnológica e operacional e do rigor empregado na qualificação de componentes e subsistemas nos processos de integração e montagem.
No dia de seu aniversário de dez anos, o SCD-2 completou 52.807 voltas ao redor da Terra. Em uma década, percorreu a distância de 2,36 bilhões de quilômetros, o que corresponde a 3,1 mil viagens de ida e volta à Lua. Sua velocidade orbital é cerca de 27 mil km/h. Desde o lançamento, foram realizadas 33 manobras de reorientação do eixo de rotação e 29 de incremento da velocidade de rotação.
O SCD-1 e o SCD-2 integram, junto com o satélite sino-brasileiro CBERS-2B, este em operação há um ano, o Sistema Brasileiro de Coleta de Dados Ambientais. A missão é retransmitir para uma estação receptora os dados coletados por uma rede de aproximadamente 750 plataformas automáticas de coleta de dados ambientais distribuídas ao longo do território nacional.
Quando os satélites passam sobre a região de visibilidade das estações de rastreio de Cuiabá (MT) e de Alcântara (MA), onde estão localizadas as antenas para contato, os sinais das plataformas que se encontram visíveis aos veículos são captados e retransmitidos à estação. Ali, os dados recebidos são gravados e, após a passagem do satélite, transmitidos ao Centro de Missão de Coleta de Dados, em Cachoeira Paulista (SP), onde são processados e distribuídos aos usuários.
Os dados são utilizados em diversas aplicações, como previsão de tempo, estudos sobre correntes oceânicas, marés, química da atmosfera, planejamento agrícola.
Uma aplicação de grande relevância é o monitoramento das bacias hidrográficas, que fornece dados fluviométricos e pluviométricos. Os dados estão disponíveis no endereço

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Milky Way's fastest stars may be immigrants

Hypervelocity stars are racing out of the Milky Way (Illustration: Ruth Bazinet/CfA)
Hypervelocity stars are racing out of the Milky Way (Illustration: Ruth Bazinet/CfA)

O fim anunciado da Phoenix

Neve em Marte Crédito: NASA
Ao fim de poucos meses, a missão da sonda americana Phoenix está prestes a terminar. Habituados como estamos à duradoura prestação dos dois rovers (Spirit e Opportunity), este facto pode provocar alguma estranheza. Contudo, não existem razões para tal: a posição da sonda na superfície de Marte
Marte é o quarto planeta do Sistema Solar, a contar do Sol. É o último dos chamados planetas interiores. O seu diâmetro é cerca de 50% mais pequeno do que o da Terra e possui uma superfície avermelhada, sendo também conhecido como planeta vermelho.
não lhe permite resistir muito mais tempo, já que o Sol
O Sol é a estrela nossa vizinha, que se encontra no centro do Sistema Solar. Trata-se de uma estrela anã adulta (dita da sequência principal) de classe espectral G. A temperatura na sua superfície é aproximadamente 5800 graus centígrados e o seu raio atinge os 700 mil quilómetros.
mergulha para o horizonte e as temperaturas baixam, trazendo o gelo (ou melhor, os gelos, de água e de dióxido de carbono) que há-de encerrar a sonda num túmulo branco. Mas até lá, a sonda prossegue na sua missão, analisando amostras de solo e perscrutando o que se passa na atmosfera
1- Camada gasosa que envolva um planeta ou uma estrela. No caso das estrelas, entende-se por atmosfera as suas camadas mais exteriores. 2- A atmosfera (atm) é uma unidade de pressão equivalente a 101 325 Pa.
Foi assim que foi detectada a formação e queda de neve a cerca de 4 km de altitude; porém, até agora, não parece haver evidências de que essa neve tenha atingido o solo do planeta
Um planeta é um objecto que se forma no disco que circunda uma estrela em formação e cuja massa é superior à de Plutão (1/500 da massa da Terra) e inferior a 10 vezes a massa de Júpiter. Ao contrário das estrelas, os planetas não produzem luz, apenas reflectem a luz da estrela que orbitam.
vermelho. Quanto ao solo, foi anunciado que tinha sido identificada a presença de partículas de carbonatos – outra prova, se necessário fosse, do papel que a água desempenhou no passado do planeta. Convém referir, ainda assim, que estas minúsculas partículas podem ter tido origem noutra região do planeta, e que a sua idade é de todo desconhecida.
Entretanto, a câmara MARDI, de que se fala noutra peça, vai ser usada para obter imagens detalhadas da área sob a sonda em que há gelo exposto (consequência da aterragem, feita com recurso a pequenos jactos) e muito provavelmente também para tentar perceber a natureza dos grãos que se acumularam na estrutura do trem de aterragem da Phoenix, e que parecem crescer e mudar de posição ao longo do tempo.

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Índia lança primeiro satélite à Lua

da France Presse, em Sriharikota (Índia)
A primeira missão indiana à Lua foi lançada na manhã desta quarta-feira do Centro Espacial de Sriharikota, no sudeste da Índia. O foguete indiano PSLV partiu às 6h22 local (22h52 Brasília), levando o satélite Chandrayaan-1, equipado com uma sonda lunar.
O lançamento da missão não tripulada transcorreu como previsto, disse um responsável do centro espacial.
O foguete PSLV deve colocar em órbita o Chandrayaan-1 a 385.000 km da Terra e o satélite realizará uma série de experiências e observações envolvendo a Lua, durante dois anos, incluindo estudos topográficos e busca de minerais e substâncias químicas.
O projeto Chandrayaan-1, avaliado em US$ 80 milhões, deve preceder outra missão semelhante, em 2010 ou 2012, segundo a agência espacial indiana, que planeja mandar um homem ao espaço.

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New Eye on the Outer Solar System Launches Successfully

Written by Nancy Atkinson
The Interstellar Boundary Explorer.  Credit: NASA

The Interstellar Boundary Explorer. Credit: NASA

There's a new spacecraft in Earth orbit, with a really "far out" mission: to map the outer solar system. NASA's Interstellar Boundary Explorer mission, or IBEX launched successfully from the Kwajalein Atoll in the Pacific Ocean at 1:47 p.m. EDT, Sunday, from an Orbital Sciences Pegasus XL launch vehicle. IBEX will be the first spacecraft to image and map dynamic interactions taking place in the outer solar system. The two Voyager probes sent back a limited amount of information about the region of space where our solar system ends and interstellar space begins. But beyond that, not much is known about this area. The region is about three times further from the sun than the orbit of planet Pluto. "No one has seen an image of the interaction at the edge of our solar system where the solar wind collides with interstellar space," said IBEX Principal Investigator David McComas of the Southwest Research Institute in San Antonio. "We know we're going to be surprised."

The spacecraft separated from the third stage of its Pegasus launch vehicle at 1:53 p.m. and immediately began powering up components necessary to control onboard systems. The operations team is continuing to check out spacecraft subsystems.

"After a 45-day orbit raising and spacecraft checkout period, the spacecraft will start its exciting science mission," said IBEX mission manager Greg Frazier of NASA's Goddard Space Flight Center in Greenbelt, Md.

"The heliosphere's boundary region is enormous, and the Voyager crossings of the termination shock, while historic, only sampled two tiny areas 10 billion miles (16 billion km) apart," NASA scientist Eric Christian said.

Voyager 1 passed the inner boundary in 2004 and Voyager 2 crossed over last year.

The solar wind, a stream of electrically conducting gas continuously moving outward from the sun at 1 million mph (1.6 million kph), blows against this interstellar material and forms a huge protective bubble around the solar system. This bubble is called the heliosphere.

As the solar wind reaches far beyond the planets to the solar system's outer limits, it encounters the edge of the heliosphere and collides with interstellar space. A shock wave is present at this boundary.

"Every six months, we will make global sky maps of where these atoms come from and how fast they are traveling. From this information, we will be able to discover what the edge of our bubble looks like and learn about the properties of the interstellar cloud that lies beyond the bubble," physicist Herb Funsten of the U.S. Department of Energy's Los Alamos National Laboratory.

Sources: NASA, Reuters


Lucimary Vargas
Observatório Astronômico Monoceros
Além Paraíba-MG-Brasil

Did Lightning and Volcanoes Spark Life on Earth?

Written by Nancy Atkinson
Chilean Volcano in 2008 creates lightning.  Credit: AP

Chilean Volcano in 2008 creates lightning. Credit: AP

Maybe the fictional Dr. Frankenstein wasn't so crazy after all. Two scientists have resurrected an old experiment, breathing life into a "dead" notion about how life began on our planet. New analysis shows that lightning and gases from volcanic eruptions could have given rise to the first life on Earth.

"It's alive!"…

Back in the early 1950s, two chemists Stanley Miller and Harold Urey of the University of Chicago did an experiment that tried to recreate the conditions of a young Earth to see how the building blocks of life could have arisen. They used a closed loop of glass chambers and tubes with water and different mixes of hydrogen, ammonia, and methane; the gases thought to be in Earth's atmosphere billions of years ago. Then they zapped the mixture with an electrical current, to try and confirm a hypothesis that lightning may have triggered the origin of life. After a few days, the mixture turned brown.
When Miller analyzed the water, he found it contained amino acids, which are the building blocks of proteins — life's toolkit. The spark provided the energy for the molecules to recombine into amino acids, which rained out into the water. The experiment showed how simple molecules could be assembled into the more complex molecules necessary for life by natural processes, like lightning in Earth's primordial atmosphere.
The apparatus used for Miller's original experiment. Credit: NASA
But there was a problem. Theoretical models and analyses of ancient rocks eventually convinced scientists that Earth's earliest atmosphere was not rich in hydrogen, so many researchers thought the experiment wasn't an accurate re-creation of early Earth. But the experiments performed by Miller and Urey were ground-breaking.

"Historically, you don't get many experiments that might be more famous than these; they re-defined our thoughts on the origin of life and showed unequivocally that the fundamental building blocks of life could be derived from natural processes," said Adam Johnson, a graduate student with the NASA Astrobiology Institute team at Indiana University, Bloomington. Johnson is the lead author on a paper that resurrects the old origin-of-life experiments, with some tantalizing new findings.

Miller died in 2007. Two former graduate students of Miller's –geochemists Jim Cleaves of the Carnegie Institution of Washington (CIW) in Washington, D.C., and Jeffrey Bada of Indiana University, Bloomington–were examining samples left in Miller's lab. They found the vials of products from the original experiment and decided to take a second look with updated technology. Using extremely sensitive mass spectrometers at NASA's Goddard Space Flight Center Cleaves, Bada, Johnson and colleagues found traces of 22 amino acids in the experimental residues. That is about double the number originally reported by Miller and Urey and includes all of the 20 amino acids found in living things.

Miller actually ran three slightly different experiments, one of which injected steam into the gas to simulate conditions in the cloud of an erupting volcano. "We found that in comparison to Miller's classic design everyone is familiar with from textbooks, samples from the volcanic apparatus produced a wider variety of compounds," said Bada.

This is significant because thinking on the composition of Earth's early atmosphere has changed. Instead of being heavily laden with hydrogen, methane, and ammonia, many scientists now believe Earth's ancient atmosphere was mostly carbon dioxide, carbon monoxide, and nitrogen. But volcanoes were active during this time period, and volcanoes produce lightning since collisions between volcanic ash and ice particles generate electric charge. The organic precursors for life could have been produced locally in tidal pools around volcanic islands, even if hydrogen, methane, and ammonia were scarce in the global atmosphere.

So, this breathes life into the notion of lightning jump-starting life on Earth. Although Earth's primordial atmosphere was not hydrogen-rich, gas clouds from volcanic eruptions did contain the right combination of molecules. Is it possible that volcanoes seeded our planet with life's ingredients? While no one knows what happened next, the researchers are continuing their experiments in an attempt to determine if volcanoes and lightning are the reasons we're here.

The paper was published in Science on Oct. 17, 2008

Sources: NASA, ScienceNOW



Lucimary Vargas
Observatório Astronômico Monoceros
Além Paraíba-MG-Brasil

Plumes of methane identified on Mars

Finding could influence choice of landing site for Mars Science Laboratory.

Eric Hand

Ithaca, New York

More than four years after researchers first said they had found methane gas on Mars, a scientist claims that he has "nailed" the controversial detection and identified key sources of the gas.


Nili Fossae is a hotspot for martian methane, says Michael Mumma (below).
Nili Fossae is a hotspot for martian methane, says Michael Mumma (below).JPL-Caltech/Univ. Arizona/NASA

On Earth, methane is mostly biological in origin; on Mars, it could signal microbes living deep underground. The latest work suggests that martian methane is concentrated in both space and time — at a handful of hotspots hundreds of kilometres across, plumes of methane bloom and dissipate in less than a year.
News of the detection is rippling through the Mars community just months before a destination is picked for the Mars Science Laboratory (MSL), the US$2-billionrover that is due to launch in 2009. It will carry an instrument that could both detect trace amounts of methane and help discern whether it is of biological or geological origin. One of the proposed methane plumes blankets one of the seven possible landing sites: Nili Fossae, which was given a middling ranking by the science community after a September evaluation that did not consider the emerging methane results.
"Now we've got these little signposts saying: 'Look, here I am. Come here!'" says Michael Mumma, a planetary scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. He presented his team's work on 11 October at a meeting of the American Astronomical Society in Ithaca, New York.

Michael MummaMichael Mumma, of NASA's Goddard Space Flight Center in Greenbelt, Maryland.NASA

Mumma has been arguing for methane on Mars since 2003, when other startling findings began to emerge. One group, using the Canada-France-Hawaii Telescope on Mauna Kea, Hawaii, found global trace methane levels of 10 parts per billion, but could see no more detail than that. A second group, using thousands of spectra taken by the European Space Agency's Mars Express orbiter, found similar global levels, with hints of regional variability in concentration (V. Formisano et  al. Science 306, 1758–1761; 2004). But some of that paper's impact was diluted when the lead investigator, Vittorio Formisano of the Institute of Physics and Interplanetary Space in Rome, made separate claims of ammonia and formaldehyde that have not been confirmed.
Mumma, a spectroscopy expert, obtained data from telescopes in Hawaii and Chile that supported the notion of methane hotspots.
Now he says he knows for sure and is ready to publish. Having obtained four more years of data, Mumma has confirmed the presence of methane by matching four lines in his infrared spectra of the planet's atmosphere to the characteristic signature of methane — a more definite determination than previous analyses — and found more evidence that the methane is localized in discrete hotspots, which peak at levels of 60 parts per billion. "His numbers have changed a lot over time. But Mike has made a pretty compelling case," says Steven Squyres, a planetary scientist at Cornell University in Ithaca, and principal investigator for the Mars rovers Spirit and Opportunity.

"Now we've got these little signposts saying: 'Look, here I am. Come here!'"

More important than the peak concentrations, Mumma says, are the short lifetimes of the plumes. Previously, methane was thought to be destroyed in the atmosphere by sunlight — a slow process that allows the gas to mix in the atmosphere and persist for about 300 years. A global level of 10 parts per billion and a lifetime of hundreds of years means that a few hundred tonnes of methane are entering the atmosphere each year: the work of a few thousand cows. But plumes of 60 parts per billion that live for less than a year imply a methane-production rate several orders of magnitude higher. "This is a big deal," says Sushil Atreya of the University of Michigan in Ann Arbor, a co-author of the 2004 Mars Express paper.
Whether the methane plumes are biological or geological in origin is impossible to know at the moment, says Atreya. For example, microbes could be living in deep groundwater below a perma­frost zone, and their waste methane could percolate up and leak out. The methane could also come from chemical reactions in which buried volcanic rocks rich in the mineral olivine interact with water. A third possibility is that the methane is escaping from buried clathrates, deposits of methane ice formed long ago by one of the other two mechanisms.
But NASA's next Mars rover will be able to analyse, at levels of parts per trillion, the fractional concentrations of the carbon isotopes in each methane molecule. Life on Earth prefers to process lighter carbon-12 atoms. And so, on Mars, methane freighted with carbon-12 could be a sign of a biological origin.
John Grotzinger, a geologist at the California Institute of Technology in Pasadena and project scientist for the MSL, says the methane detection could be important in deciding the MSL's destination. "We're going to take this very seriously," he says. "We all need to sit back and evaluate the data and find out if Nili Fossae is the only place where this occurs." The methane results could be considered at a meeting early next month, when the seven sites are evaluated from an engineering and safety standpoint.
A reshuffling of the sites' rankings could be in order, Grotzinger adds, but he wants some hard data to consider. "Talks don't count. The paper needs to be published," he says.
A paper describing Mumma's work is under review at Science.
Lucimary Vargas
Observatório Astronômico Monoceros
Além Paraíba-MG-Brasil


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