terça-feira, 5 de fevereiro de 2008

Asteróide passa a 550 mil quilômetros da Terra

France Presse, em Washington
O asteróide batizado de 2007 TU24 passou próximo à Terra nesta terça-feira (29), como previsto, e em nenhum momento apresentou risco de colisão com o nosso planeta, indicou o JPP (Jet Propulsion Laboratory), da Nasa (agência espacial norte-americana).
"Confirmamos a passagem do asteróide como previsto", afirmou D.C Agle, porta-voz do JPL, em Pasadena, na Califórnia (EUA).
O objeto passou a 550 mil quilômetros da Terra às 03h33 no horário de Brasília desta terça-feira, antes de se afastar. A Nasa conseguiu tirar fotografias do asteróide com radares.
O objeto foi descoberto há três meses, em outubro, pelo programa de vigilância da Universidade norte-americana do Arizona.
Por um triz
De acordo com o Centro dos Planetas Menores da União Astronômica Internacional, com sede em Paris, o asteróide mais próximo que passou na Terra, e foi detectado, foi o FU162, que em 31 de março de 2004 esteve a 6.500 quilômetros.
Nesta quarta-feira (30), o asteróide 2007 WD5 deve se aproximar 26.000 quilômetros de Marte, uma distância considerada ínfima em termos espaciais.
Apesar da pouca distância, o evento mostrou-se uma decepção para os astrônomos, que inicialmente pensavam que havia a possibilidade de que ele se chocasse com o planeta vermelho. A colisão, levando-se em conta seu tamanho de 50 metros, seria o equivalente ao de uma bomba nuclear de três megatons.
Um objeto semelhante teria se chocado em Tunguska, na Sibéria, em 1908, arrasando 80 milhões de árvores em uma área de 2.200 quilômetros quadrados.

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Lucimary Vargas
Além Paraíba-MG-Brasil

Pools of Invisible Matter Mapped in Space

By Jeanna Bryner
Staff Writer
posted: 17 January 2008
06:10 am ET

A new map reveals dense pools of invisible matter tipping the scales at 10 trillion times the mass of the sun and housing a cosmic city of ancient galaxies.

The map, presented last week at a meeting of the American Astronomical Society in Austin, Texas, provides indirect evidence for so-called dark matter and how this mysterious substance affects galaxy formation.

Scientists theorize that dark matter, considered to make up about 85 percent of the universe's matter, acts as scaffolding on which galaxies mature. As the universe evolves, the tug from dark matter's gravitational field causes galaxies to collide and swirl into superclusters.

It's all these gravitational effects, from something that can't be seen, that indicates dark matter exists.

"The dark matter halos are what allow the galaxies to form in the first place. The dark matter is the underlying skeleton of the universe," said Meghan Gray of the University of Nottingham in the United Kingdom, who was part of the map-making team. "Most of the universe is dark matter. Galaxies are just froth on this ocean of dark matter."

Uncovering invisible matter

Gray, Catherine Heymans of the University of British Columbia in Vancouver and colleagues used NASA's Hubble Space Telescope to observe a supercluster called Abell 901/902, which resides 2.6 billion light-years from Earth and spans more than 16 million light-years across.

The astrophysicists measured light from a backdrop of more than 60,000 galaxies after it passed through the supercluster and its dark matter. According to Einstein's general relativity theory, the presence of matter can bend spacetime, deflecting the path of a light ray passing through the mass.

"Dark matter leaves a signature in distant galaxies" explained study co-author Ludovic Van Waerbeke of the University of British Columbia. "For example, a circular galaxy will become more distorted to resemble the shape of a banana if its light passes near a dense region of dark matter."

By averaging the shape-distortions from the thousands of galaxies, the researchers found four pools of dark matter. And the invisible clumps matched up with the location of hundreds of ancient galaxies, which have experienced a violent history in their passage from the outskirts of the supercluster into the central hubs.

"If the supercluster wasn't there, you'd still see all of these galaxies in the background," Gray told SPACE.com. "But you put this massive object [in front of them] and your view gets distorted. It's a cosmic optical illusion."

Aging galaxies

The survey's broader goal is to understand how galaxies are influenced by the environment in which they live.

"The new map of the underlying dark matter in the supercluster is one key piece of this puzzle," Gray said. "At the same time, we're looking in detail at the galaxies themselves."

The galaxies in the central hubs, they are finding, show signs of aging, as they are elliptical, red in color and are no longer forming stars. Disk galaxies reside on the outskirts of the supercluster. These youthful galaxies are blue-hued and buzzing with star birth.

It's these young galaxies that constantly fall into the supercluster, adding to its galactic girth.

"As they come in, either they're interacting with each other more or they're interacting with the dark matter," Gray explained. "Something is happening to change their properties."

The team plans to study individual galaxies in an effort to understand how this supercluster environment shapes and changes galaxies.

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Lucimary Vargas
Além Paraíba-MG-Brasil

Using GPS Could Better Tsunami Warning System

Written by Nicholos Wethington
tsunami_jas_2004361.jpgWhen there is a tsunami coming towards your home, you want to know about it as far in advance as possible. An early warning about such a disaster could save countless lives, and using Global Positioning System information may just be the way to speed up our reaction time in the future.
The traditional tsunami warning system relies on measuring the magnitude of the earthquake that causes the tsunami. This method is not always reliable, though, as calculating accurately the power of the resulting ocean waves takes hours or days.
For example, 2005 Nias quake near Indonesia was estimated to cause about the same size of tsunami as the powerful 2004 Indian Ocean quake, which destroyed cities in portions of Indonesia, India and Thailand and killed more than 225,000 people. The 2005 tsunami did not nearly meet the same proportions as the earlier quake. There have been five false tsunami alarms between 2005 and 2007, which can reduce the effectiveness of the warnings in the eye of the public.
In a study published in the December Geophysical Research Letters, researcher Y. Tony Song of NASA's Jet Propulsion Laboratory in Pasadena, California, showed that using GPS from coastal areas near the epicenter of the quake could help more accurately and quickly determine the scale of a tsunami.
Here's how it would potentially work: data from seismometers near the earthquake's epicenter is first registered, as in the traditional system. After that, GPS data of the seafloor displacement is factored in, which gives a more complete picture of the extent and power of the earthquake. The size of the predicted tsunami is then quickly calculated and given a number between 1 and 10 – 1 being the lowest – much like the Richter scale. This information could then be passed through the tsunami warning system to evacuate people to safety.
GPS data helps create a 3-dimensional model of the tsunami by giving details about the horizontal and vertical displacement of the seafloor, and this data can be sent and analyzed in minutes from coastal GPS stations. Song's methods have accurately modeled three previous tsunamis: one in Alaska in 1964, the Indian Ocean tsunami in 2004, and the 2005 Nias tsunami.
Source: JPL Press Release

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Lucimary Vargas
Além Paraíba-MG-Brasil

Moon Stuck

Space leaders work to replace lunar base with manned asteroid missions

Posted: January 18, 2008


Some of the most influential leaders of the space community are quietly working to offer the next U.S. president an alternative to President Bush's "vision for space exploration"--one that would delete a lunar base and move instead toward manned missions to asteroids along with a renewed emphasis on Earth environmental spacecraft.

Top U.S. planetary scientists, several astronauts and former NASA division directors will meet privately at Stanford University on Feb. 12-13 to define these sweeping changes to the NASA/Bush administration Vision for Space Exploration (VSE).

Abandoning the Bush lunar base concept in favor of manned asteroid landings could also lead to much earlier manned flights to Mars orbit, where astronauts could land on the moons Phobos or Deimos.

Their goals for a new array of missions also include sending astronauts to Lagrangian points, 1 million mi. from Earth, where the Earth's and Sun's gravity cancel each other out and spacecraft such as replacements for the Hubble Space Telescope could be parked and serviced much like Hubble.

The "alternate vision" the group plans to offer would urge far greater private-sector incentives to make ambitious human spaceflight plans a reality.

There would also be some different "winners and losers" compared with the Bush vision. If the lunar base is deleted, the Kennedy Space Center could lose additional personnel because there would be fewer Ares V launches and no lunar base infrastructure work that had been assigned to KSC. On the other hand, the Goddard Space Flight Center and National Oceanic and Atmospheric Administration near Washington, along with the Jet Propulsion Laboratory (JPL) in California, would gain with the increased space environmental-monitoring goal.

Numerous planetary managers told Aviation Week & Space Technology they now fear a manned Moon base and even shorter sorties to the Moon will bog down the space program for decades and inhibit, rather than facilitate, manned Mars operations--the ultimate goal of both the Bush and alternative visions. The first lunar sortie would be flown by about 2020 under the Bush plan.

If alternative-vision planners have their way, the mission could instead be flown to an asteroid in about 2025.

Participants in the upcoming meeting contend there's little public enthusiasm for a return to the Moon, especially among youth, and that the Bush administration has laid out grandiose plans but has done little to provide the funding to realize them on a reasonable timescale.

Planners say the Bush plan is beginning to crumble, with only companies that have won major funding still enthusiastic about the existing plan.

"It's becoming painfully obvious that the Moon is not a stepping-stone for manned Mars operations but is instead a stumbling block," says Robert Farquhar, a veteran of planning and operating planetary and deep-space missions.

The prospect of challenging new manned missions to asteroids is drawing far more excitement among young people than a "return" (as in going backward) to the Moon, says Lou Friedman, who heads The Planetary Society, the country's largest space interest group.

The society is co-hosting the invitation-only VSE replanning session with Stanford. A lot of people going to the meeting believe "the Moon is so yesterday," says Friedman.

"It just does not feel right. And there's growing belief that, at high cost, it offers minimal engineering benefit for later manned Mars operations."

Under the alternative VSE, even smaller, individual lunar sorties would be reduced, or perhaps deleted entirely, says Noel W. Hinners, who had extensive Apollo lunar science and system responsibility at Bell Laboratories before heading all of NASA's science program development. He also led Lockheed Martin Spaceflight System.

Hinners believes the group should examine dropping all the lunar sorties to accelerate the human push to Mars in the revised VSE proposal to the new administration.

The James Webb Space Telescope, with a 21.3-ft.-dia. mirror, will be launched in 2013 to one of these "L" points. With little fanfare, it was recently approved to carry a lightweight Crew Exploration Vehicle docking system just in case a manned CEV has to make a house call a million miles from Earth for emergency servicing.

A growing corps of scientists, engineers and astronauts are emerging to argue for this chance to accelerate manned spaceflight operations outward well beyond the Moon--faster toward Mars than can be done by using the Moon as a stepping-stone only 240,000 mi. away.

"The notion that the Moon could serve as a proving ground for Mars missions strains credulity," says Farquhar, who holds the Charles A. Lindbergh Chair for Aerospace at the Smithsonian National Air and Space Museum. He also was mission director for the Applied Physics Laboratory's Near Earth Asteroid Rendezvous mission that was the first to land a spacecraft on an asteroid.

A return to manned Moon operations has become "a bridge too far" in the Bush administration's VSE, says Wes Huntress, another former planetary mission manager.

Huntress is director of the Washington-based Carnegie Institution's Geophysical Laboratory and had a long career at JPL and NASA headquarters, where he led NASA space science development and operations--including the highly successful Discovery planetary mission series. He's also helping to organize the Stanford workshop that will have about several dozen participants, including several top NASA and contractor exploration managers.

"There is little left of the 2004 Vision for Space Exploration except the real need to retire the space shuttle," he says. "Even this goal is being pursued with great sacrifice from all other parts of the agency because the administration has simply not put its money where its mouth is."

"Inadequate NASA budgets are leading to collapse of the VSE Moon focus and to incredibly slow progress for the Moon," says Hinners.

"The nation's space enterprise is under great strain even to build Ares I and Orion CEV," Huntress stresses. "There are alternate destinations for human deep-space missions that do not require building a lot of new hardware to [come and go between Earth and the Moon]. These are missions to near-Earth asteroids or to scout the Sun-Earth Lagrangian points for future space telescope construction and servicing," he notes.

The Earth-Sun Lagrangian points (also called libration points) are at the very edge of the Earth's gravitational well, and a mission would represent a first excursion to the limit of Earth's influence in the Solar System--a significant step beyond Apollo, says Huntress.

Missions sent to "L" points can stop just there, orbiting only above and below the ecliptic plane without any significant use of station-keeping fuel. Also, L points offer a much cleaner option for advanced astronomy than the dusty lunar surface, where you have to land everything in addition to launching it.

"As the nation seems to be turning to environmental threats to our own planet, a mission to a near-Earth asteroid to assess their nature for good or ill would also seem to be a real winner," says Huntress.

These stepping-stones would allow for the development of a broader vision of human spaceflight than simply reinventing Apollo.

Major lunar-related contracts for the Constellation Crew Exploration Vehicle Orion command ship, a lunar lander design and Ares V launcher have yet to be awarded, giving the next administration some breathing room in post-Bush administration VSE contracting.

Some basic asteroid mission design work--part of it volunteer--using the CEV hardware is already underway at the Johnson Space Center (AW&ST Sept. 25, 2006, p. 21). Other, more in-depth and long-standing manned asteroid analysis is underway under International Astronautical Assn. and Smithsonian National Air and Space Museum sponsorship.

Scott Hubbard, consulting professor in the Stanford Aeronautics and Astronautics Dept., conceived the reassessment meeting. Hubbard was previously the director of NASA Ames Research Center and, before that, NASA Mars program director. "We have planned this invitation-only workshop to elicit frank and open discussion about the future of the 'vision' as the administration changes," he says.

"The Stanford workshop will address a broad range of issues touching on many elements of space exploration. The attendees will discuss the balance between space science and human exploration, the need for continuing and enhancing Earth science observations, the relative utility of humans and robotics, and progress or impediments to human exploration of Mars, asteroids and the Moon," says Hubbard. "In addition, the workshop will discuss the status of access to space and the emerging entrepreneurial space industry.

"This is the kind of debate that will go on--beyond whether a lunar base really makes sense. But manned asteroid missions first--ahead of a lunar base--are drawing strong attention," he says. Hubbard and Friedman are co-hosting the event, along with former astronaut Kathy Thornton, associate dean of the University of Virginia's Science, Technology and Society Dept. Thornton flew on four space shuttle missions, including the initial critical repair of the Hubble Space Telescope in 1993.

The alternative vision would also include far greater private-sector incentives for participation at all levels, an area public surveys cite as very important. Missions to asteroids and Lagrangian points, for example, are likely to carry along Bigelow-type commercial inflatable modules. A recent informal space program survey by The New York Times found substantial public frustration about NASA's doing what entrepreneurs could do better.

Under the alternative concepts, astronauts using an upgraded CEV would initially be sent on long-duration missions, not to the Moon, but to land on asteroids where they would sample terrain perhaps more ancient than the Moon's. These visits would also help develop concepts for diverting such near-Earth objects, should they threaten a potentially devastating impact on Earth.

Although it may be hundreds of years before used operationally, an emergency asteroid diversion would be "the ultimate 'green mission'--one that could save a large portion of the Earth from impact destruction," says Friedman.

To reinforce that point, he notes that on Jan. 30, a 150-ft.-long asteroid will pass close to Mars. The asteroid visit and Lagrangian mission concepts would use much of the same CEV Ares I and Ares V heavy-lift booster infrastructure, but in ways that would be much faster stepping-stones to Mars than developing a manned lunar base. Asteroid and Lagrangian point missions would each last several weeks or months. Both the libration points and asteroids would be about 1 million mi. from Earth, requiring operations more like much longer trips to Mars at least 40-100 million mi. away.

Robotic options for all mission elements also will be reviewed, and one working group will be devoted to better defining manned versus robotic tradeoffs.

Another issue is international participation.

Aviation Week discussed an unrelated European International Space Station topic with NASA Administrator Mike Griffin last week, who in comments aside also addressed the basic Moon/Mars issues between the U.S. and Europe.

"A large portion of the scientific community in the U.S. also prefers Mars over the Moon," he acknowledged. But "interest in the Moon is driven by goals in addition to and beyond the requirements of the science community. It is driven by the imperatives that ensue from a commitment to become a spacefaring society, not primarily by scientific objectives, though such objectives do indeed constitute a part of the overall rationale.

"We continue to experience intense international interest concerning our plans for lunar exploration," Griffin told Aviation Week.

With Frank Morring, Jr., in Washington.

This story appears in the Jan. 21 issue of Aviation Week & Space Technology, p. 24

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Lucimary Vargas
Além Paraíba-MG-Brasil

Circumstellar dust takes flight in 'The Moth'

Posted: January 20, 2008

What superficially resembles a giant moth floating in space is giving astronomers new insight into the formation and evolution of planetary systems.

This is not your typical flying insect. It has a wingspan of about 22 billion miles. The wing- like structure is actually a dust disk encircling the nearby, young star HD 61005, dubbed "The Moth." Its shape is produced by starlight scattering off dust.

See larger image here
Dust disks around roughly 100-million-year-old stars like HD 61005 are typically flat, pancake-shaped structures where planets can form. But images taken with NASA's Hubble Space Telescope of "The Moth" are showing that some disks sport surprising shapes.

"It is completely unexpected to find a dust disk with this unusual shape," said senior research scientist Dean Hines of the Space Science Institute, New Mexico Office in Corrales, New Mexico, and a member of the Hubble team that discovered the disk. "We think HD 61005 is plowing through a local patch of higher-density gas in the interstellar medium, causing material within HD 61005's disk to be swept behind the star. What effect this might have on the disk, and any planets forming within it, is unknown."

Hines called this possible collision "unusual, because we don't expect very much interstellar material to be in the solar neighborhood. That's because the area through which our Sun is moving was evacuated within the past few million years by at least one supernova, the explosion of a massive star. Yet, here's evidence of dense material that's very close, only 100 light-years away."

Astronomers have found evidence that the environment in which a star forms influences its prospects for planet formation. Hubble has actually seen that young planet-forming disks can be affected directly by their environment. The harsh stellar radiation from the Trapezium stars in the Orion Nebula has altered some disks. It is unclear, however, what effect passage through a cloud similar to the one in which HD 61005 finds itself would have on planet formation. Researchers have speculated that passage through dense regions of the interstellar medium could impact the atmospheres of evolving planets.

The Moth is part of a survey of Sun-like stars that Hines and collaborators observed with Hubble's Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) and NASA's Spitzer Space Telescope to study the formation and evolution of planetary systems. Under the lead of Michael Meyer of the University of Arizona in Tucson, the team initially used Spitzer to look for heat radiation‹the tell-tale sign of dust warmed by the star‹to identify interesting star systems.

Hines then teamed with Glenn Schneider of the University of Arizona to use Hubble's high- contrast imaging capability of the NICMOS coronagraph to image these disks and reveal where the dust detected by Spitzer resides. The NICMOS coronagraph blocked out the starlight so that astronomers could see details in the surrounding disk.

"These symbiotic capabilities, uniquely implemented in NASA's Great Observatories, provide astronomers with the powerful observational tools to study the circumstellar environments of potentially planet-forming systems," Schneider said.

Added Meyer: "Combining observations from these two spacecraft gives us information about the composition of the dust grains, whether they're icy or sandy, or whether they're like the sooty smoke particles rising from a chimney. The composition and sizes of the dust can tell us a lot about the dynamics and evolution of a solar system. In our solar system, for example, astronomers have evidence of rocks smashing into each other and generating dust, as in the asteroid and Kuiper belts. We're seeing these same processes unfold in other planetary systems."


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Lucimary Vargas
Além Paraíba-MG-Brasil

Cosmic mid-life crisis

A new study of 'GEMS' from Hubble and Spitzer reveals cosmic fireworks fizzled out when the universe reached middle age.
Provided by the McDonald Observatory
One of the many interacting galaxy pairs seen by the GEMS survey with the Hubble Space Telescope. S. Jogee/UT-Austin/GEMS Collaboration/STScI/NASA [View Larger Image]
January 18, 2008
We all start to party less around middle age, and new studies by a team led by University of Texas at Austin astronomer Shardha Jogee now finds that the universe, as a whole, is no exception.

According to the current models of galaxy formation, dubbed "hierarchical lambda cold dark matter" models, galaxies built up to their current masses, shapes, and sizes through the successive mergers of less massive protogalaxies made of gas, stars, and dark matter. In the first quarter of the universe's lifespan, the cosmic landscape was dominated by violent galaxy mergers, which could radically transform the shape of a galaxy and convert its gas into stars at an extreme rate. More than half of bright galaxies were indulging in such violent "partying."

New research is showing that all changed when the universe hit middle age. "Our study finds that over the last 7 billion years, after the universe hit its mid-forties, so to speak, it transitioned from a violent merger-driven mode into a quieter mode," Jogee says.

She and her team find that over each billion-year interval, only 10 percent of galaxies are typically involved in strong interactions and mergers.

Jogee's team has analyzed more than 5,000 galaxies imaged by Hubble Space Telescope as part of GEMS, one of the largest-area surveys conducted with Hubble in two filters.
This Hubble image shows another interacting galaxy pair. S. Jogee/UT-Austin/GEMS Collaboration/STScI/NASA [View Larger Image]
"With Hubble's spectacular resolution," says Kyle Penner, member of the international GEMS collaboration. "We could discern amazing tell-tale clues of the mergers and interactions, huge tails, warps, ripples, double nuclei, in galaxies billions of light-years away."

"It's been exciting to apply different complementary techniques in this large survey and to sift through the merger history of the universe during this elusive era," says Sarah Miller, member of the international GEMS collaboration.
In addition to estimating the frequency of mergers, Jogee and her colleagues found that contrary to what is commonly assumed, the average star formation rate in these interacting and merging galaxies is only enhanced by a modest factor of two to three compared to that in normal non-interacting galaxies.

"While extreme bursts of star formation, so-called cosmic fireworks, may happen in some galaxy mergers or interactions, they are not the norm in the vast majority of galaxy interactions taking place over the last 7 billion years," Jogee says.

The findings of Jogee's team result from a powerful synergy of data from NASA's Hubble and Spitzer space telescopes. "Mid-infrared observations from the Spitzer Space Telescope, taken by George Rieke of The University of Arizona, were key for tracing hidden star formation, obscured by dust," Jogee says. "The exquisite resolution of the GEMS Hubble data in turn allowed us to identify strongly interacting and merging galaxies at much earlier cosmological times than conventional ground-based telescopes," says team member Daniel McIntosh of the University of Massachusetts, Amherst.

Jogee and her team, in fact, find that only 20 percent of the total cosmic star formation that took place over the last 7 billion years appears to come from strongly interacting and merging galaxies. These results extend the similar trend found for a smaller sample of about 1,500 galaxies over a narrower time interval by fellow team members Christian Wolf from Oxford University and Eric Bell of the Max Planck Institute of Astronomy.

Furthermore, the results reported by Jogee and her team on the modest fraction (about 20 percent) of merger-induced star formation, and the frequency of galaxy mergers over the last 7 billion years, are in remarkably good agreement with prevailing theoretical cold dark matter models of galaxy evolution.

According to team member Rachel Somerville of the Max Planck Institute of Astronomy, "Mergers are thought to be a crucial process in transforming galaxies, causing bursts of star formation, and perhaps even feeding gas to the supermassive black holes lurking in the galaxy's nucleus.

"Although the frequency of mergers predicted by the models agrees quite well with the observed frequency," Somerville says, "these observations can also teach us much more about the effect these violent episodes have on galaxies."

In fact, Jogee says, "Our results raise many additional questions which can only be addressed with next generation facilities. For example, the cosmic star-formation rate is declining in normal galaxies, but it remains unclear what drives this decline. Are galaxies using up their internal cold gas supply, or is the accretion rate of gas from external filaments declining?"
This Hubble image shows one more interacting galaxy pair. S. Jogee/UT-Austin/GEMS Collaboration/STScI/NASA [View Larger Image]
Next-generation radio facilities, such as ALMA (the Atacama Large Millimeter/Sub-millimeter Array) will be critical for exploring how the cold gas content of galaxies changes over the last seven billion years, she said.

"Another key thing to note is that some of our results starkly disagree with prevailing hierarchical models of galaxy evolution," Jogee says. According to these models, the frequency of pure disk galaxies or so-called "bulgeless galaxies" is expected to be extremely low, because a past major merger in the life of every galaxy invariably builds a bulge.

Contrary to such predictions, postdoctoral fellow Fabio Barazza, formerly working with Jogee at The University of Texas and now at Geneva Observatory's Ecole Polytechnique Federale de Lausanne, found that about 20 percent of present-day spiral galaxies are bulgeless or disk-dominated, based on the analysis of about 1,000 galaxies from the Sloan Digital Sky Survey.

"We also see striking super-thin bulgeless galaxies in GEMS, at earlier epochs," Jogee says. "We yet have to characterize the frequency and origin of these enigmatic bulgeless galaxies at different epochs, but there is no denying their prevalence in the local universe."

All in all, "We have made important headway in piecing part of the cosmic puzzle of galaxy evolution, but daunting challenges loom ahead for both observers and theorists, " she says.

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Lucimary Vargas
Além Paraíba-MG-Brasil

Planets: The next generation

Two unusual older stars giving birth to a second wave of planets.
Provided by UCLA
In this image, the star BP Piscium is shown in the center in the constellation Pisces. The green and red streaks are jets of gas shot from the star. M. Perrin, UCLA/J. Graham, UC Berkeley [View Larger Image]
January 16, 2008
Hundreds of millions, or even billions, of years after planets would have initially formed around two unusual stars, a second wave of planetesimal and planet formation appears to be taking place, UCLA astronomers and colleagues believe.

"This is a new class of stars, ones that display conditions now ripe for formation of a second generation of planets, long, long after the stars themselves formed," says UCLA astronomy graduate student Carl Melis, who reported the findings today at the American Astronomical Society meeting in Austin, Texas.

"If we took a rocket to one of these stars and discovered there were two totally distinct ages for their planets and more minor bodies like asteroids, that would blow scientists' minds away," says Benjamin Zuckerman, UCLA professor of physics and astronomy and co-author of the research, which has not yet been published. "We're seeing stars with characteristics that have never been seen before."

The stars, which Melis says possess "amazing" properties for their age, are known as BP Piscium, in the constellation Pisces, and TYCHO 4144 329 2, in the constellation Ursa Major.

These two stars have many characteristics of very young stars, Melis says, including rapid accretion of gas, extended orbiting disks of dust and gas, a large infrared excess emission and, in the case of BP Piscium, jets of gas that are being shot into space. Planetesimals, like comets and asteroids, along with planets, form from the gas and dust particles that orbit young stars; planetesimals are small masses of rock or ice that merge to form larger bodies.

"With all these characteristics that match so closely with young stars, we would expect that our two stars would also be young," Melis says. "As we gathered more data, however, things just did not add up."

For example, because stars burn lithium as they get older, young stars should have large quantities of lithium. The astronomers found, however, that the spectroscopic signature of lithium in BP Piscium is seven times weaker than expected for a young star of its mass.

"There is no known way to account for this small amount of lithium if BP Piscium is a young star," Melis says. "Rather, lithium has been heavily processed, as appropriate for old stars. Other spectral measurements also indicate it is a much older star."

As seen from Earth, some 75 percent of BP Piscium's radiant energy is being converted by the dust particles into infrared light, and about 12 percent of TYCHO 4144 329 2's. These are unusually high amounts, which Melis described as "spectacular" in comparison to other stars that are known to be not young.

TYCHO 4144 329 2 orbits a companion star that has a mass similar to that of our Sun; a second generation of planets is not forming around this companion, which appears to be an ordinary old star in all respects. By studying this companion star, the astronomers have deduced that TYCHO 4144 329 2 is just 200 light-years from Earth, very close by astronomical standards. They do not know precise age of TYCHO 4144 329 2, or BP Piscium's age or distance from Earth.

The astronomers are continuing to study these stars with a variety of ground-based telescopes and with space-based observatories, including NASA's Hubble Space Telescope and Chandra X-ray Observatory, and they are searching for additional similar stars.

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Lucimary Vargas
Além Paraíba-MG-Brasil

A Possible Answer to Flyby Anomalies

Written by Ian O'Neill
The Galileo mission above Earth - the subsequent flybys caused an unexpected boost in velocity (credit: NASA)

Strange things are happening to our robotic space explorers. Also known as the "Pioneer effect" (the unexpected and sudden alterations to Pioneer 10 and Pioneer 11 trajectories measured as they continue their journey into the outer solar system), similar anomalies are being seen in flybys by modern space probes. Earth flybys by Galileo, Rosetta, NEAR and Cassini have all experienced a sudden boost in speed. After cancelling out all possible explanations, including leakage of fuel and velocity measurement error, a new study suggests the answer may lie in a bizarre characteristic of universal physics…

Planetary flybys are an essential aid to interplanetary missions to gain energy as they accelerate on their merry way to their destination. Gravity assists are accurately calculated by mission scientists so the time of arrival can be calculated down to the minute. Considering most missions take years to complete, this degree of accuracy is amazing, but essential.
So, when Galileo completed gravity assist past Earth on December 8, 1990, to speed it toward Jupiter, you can imagine NASA's surprise to find that Galileo had accelerated suddenly, and for no apparent reason. This small boost was tiny, but through the use of the Deep Space Network, extremely accurate measurements of the speeding craft could be made. Galileo had accelerated 3.9 mm/s.
This isn't an isolated case. During Earth flybys by the space probes NEAR, Cassini-Huygens and Rosetta, all experienced a unexplained boosts of 13 mm/s, 0.11 mm/s and 2 mm/s respectively. Once technical faults, observational errors, radiation pressure, magnetic instabilities and electrical charge build-up could be ruled out, focus is beginning to turn to more exotic explanations.
A recent study by Magic McCulloch suggests that "Unruh radiation" may be the culprit. The Unruh effect, put simply, suggests that accelerating bodies experience a type of electromagnetic radiation. At very low acceleration, the wavelength emitted will be so large that a whole wavelength will be longer than the dimensions of the Universe (otherwise known as the Hubble Distance). Low acceleration would therefore generate waves that have no effect on the body. However, should the accelerating body (i.e. Galileo getting accelerated by Earth's gravity during the 1990 flyby) slowly exceed an acceleration threshold, the Unruh radiation will decrease in wavelength (smaller than the Hubble Distance), causing a tiny, but measurable "boost" to its increasing velocity.
Although complex, this theory is very interesting and proves that although we can calculate the arrival time of space probes down to the nearest minute, the Universe will continue to throw up some perplexing issues for a long time yet.
Sources: arXiv Blog, arXiv abstract and paper download

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Lucimary Vargas
Além Paraíba-MG-Brasil

New information on galaxies

VLA images are unlocking galactic mysteries.
Provided by NRAO
This THINGS image shows dwarf galaxy IC2574. Walter et al., NRAO/AUI/NSF [View Larger Image]
January 16, 2008
Astronomers have produced a scientific gold mine of detailed, high-quality images of nearby galaxies that is yielding important new insights into many aspects of galaxies, including their complex structures, how they form stars, the motions of gas in the galaxies, the relationship of "normal" matter to unseen "dark matter," and many others.

An international team of scientists used more than 500 hours of observations with the National Science Foundation's Very Large Array (VLA) radio telescope to produce detailed sets of images of 34 galaxies at distances from 6 to 50 million light-years from Earth. Their project, called The HI Nearby Galaxy Survey, or THINGS, required 2 years to produce nearly one TeraByte of data. HI ("H-one") is an astronomical term for atomic hydrogen gas. The astronomers presented their initial findings to the American Astronomical Society's meeting in Austin, Texas.

"Studying the radio waves emitted by atomic hydrogen gas in galaxies is an extremely powerful way to learn what's going on in nearby galaxies. The THINGS survey uses that tool to provide sets of images of the highest quality and sensitivity for a substantial sample of galaxies of different types," says Fabian Walter, of the Max-Planck Institute for Astronomy in Heidelberg, Germany.

Most of the galaxies studied in the THINGS survey also have been observed at other wavelengths, including Spitzer space telescope infrared images and GALEX ultraviolet images. This combination provides an unprecedented resource for unraveling the mystery of how a galaxy's gaseous material influences its overall evolution.
This THINGS image shows spiral galaxy M74.
Walter et al., NRAO/AUI/NSF [View Larger Image]
Analysis of THINGS data already has yielded numerous scientific payoffs. For example, one study has shed new light on astronomers' understanding of the gas-density threshold required to start the process of star formation. "Using the data from THINGS in combination with observations from NASA's space telescopes has allowed us to investigate how the processes leading to star formation differ in big spiral galaxies like our own and much smaller, dwarf galaxies," says Adam Leroy and Frank Bigiel of the Max-Planck Insitute for Astronomy at the Austin AAS meeting.

Because atomic hydrogen emits radio waves at a specific frequency, astronomers can measure motions of the gas by noting the Doppler shift in frequency caused by those motions. "Because the THINGS images are highly detailed, we have been able to measure both the rotational motion of the galaxies and non-circular random motions within the galaxies," notes Erwin de Blok of the University of Cape Town, South Africa.

The motion measurements are providing new information about the mysterious, unseen dark matter in the galaxies. "The non-circular motions revealed by the THINGS observations, turn out to be too small to solve a long-standing problem in cosmology, namely the inability of state-of-the-art computer simulations to describe the distribution of dark matter in disk galaxies. It was thought that random motions could explain that inability, but our data show otherwise," de Blok explains.

The THINGS images revealed what Elias Brinks of the University of Hertfordshire, UK, calls a "stunning complexity of structures in the tenuous interstellar medium of the galaxies." These structures include large shells and "bubbles," presumably caused by multiple supernovae explosions of massive stars. Analyzing the detail of these complex structures will help astronomers better understand the differences in star formation processes in the varied types of galaxies.

Even such a simple question such as how big are the disks of gas in spiral galaxies had largely eluded astronomers previously. "The quality and sensitivity of the THINGS images has allowed us to see the actual edges of these disks in a large sample of galaxies," says Brinks.

The new survey also showed a fundamental difference between the nearby galaxies: part of the "current" universe, and far more distant galaxies, seen as they were when the universe was much younger. "It appears that the gas in the galaxies in the early universe is much more 'stirred up,' possibly because galaxies were colliding more frequently then and there was more intense star formation causing material outflows and stellar winds," explains Martin Zwaan of the European Southern Observatory. The information about gas in the more distant galaxies came through non-imaging analysis.

These discoveries, the scientists predict, are only the tip of the iceberg. "This survey produced a huge amount of data, and we've only analyzed a small part of it so far. Further work is sure to tell us much more about galaxies and how they evolve. We expect to be surprised," Walter says.

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Lucimary Vargas
Além Paraíba-MG-Brasil

Hubble finds saucer-shaped galaxies

A new image reveals massive disk galaxies in the early universe.
Provided by the University of Hawaii
The Hubble Space Telescope captured this massive saucer-shaped galaxy more than 9 billion light-years distant from us. Its age implies it was formed when the universe was very young. Hubble [View Larger Image]
January 22, 2008
Some of the first massive galaxies in the universe formed when huge gas clouds rapidly collapsed, according to Elizabeth McGrath of the University of California, Santa Cruz, Alan Stockton of the University of Hawaii, and their collaborators. This discovery, which is based on new Hubble Space Telescope images, challenges the commonly held idea that all of the earliest massive galaxies formed when smaller galaxies merged.

The standard theory of galaxy formation predicts that the most massive galaxies in the universe take a long time to grow, accumulating mass through the coalescence of many smaller galaxies in a process that continues until relatively recent times. To test this theory, McGrath, Stockton, and their collaborators searched for the oldest, most massive galaxies they could find and used clues from their shape and structure to deduce how they may have formed. High-resolution images from the Hubble Space Telescope revealed galaxies more massive than our own Milky Way that existed when the universe was very young, only one-fifth its current age. It is believed that such galaxies are the distant ancestors of the most massive galaxies in the universe today.

"We expected these galaxies to look similar to the football-shaped elliptical galaxies that we see at the centers of dense groups of galaxies today, where mergers are common. We were quite surprised to find that many of them appear instead to be flattened, rotating disks of ordered material," says McGrath.

Disk galaxies are pancake or saucer-shaped, and their stars orbit in circles around the center of the galaxy, much like the planets in our solar system orbit around the Sun, or like a Frisbee spins as it moves through the air. This type of galaxy is more likely to have formed from a single massive cloud that collapses under its own gravity into a flattened disk rather than through violent collisions of previously formed galaxies. Computer simulations of the latter scenario predict that collisions would destroy disks and send stars from each merging galaxy into more chaotic, three-dimensional orbits, producing football-shaped, or elliptical galaxies. The most massive galaxies in the universe today all appear to be elliptical in shape, and therefore can be quite naturally explained through the merger hypothesis. The existence of massive disk galaxies in the early universe, however, challenges this perspective.

In total, McGrath and her collaborators observed seven of what are likely some of the first massive galaxies to form in the universe. Of these, four had shapes dominated by disk-like profiles. By age-dating the galaxies from studying properties of the stars within them, McGrath's team discovered that these disk structures have remained in pristine condition for over 1 billion years. Even so, it seems inevitable that eventually these galaxies will merge with others and be reformed into the more elliptical-shaped massive, old galaxies that are familiar to us in the nearby universe.

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Lucimary Vargas
Além Paraíba-MG-Brasil

Astronomy beneficial to Arizona

A new AASTA report reveals astronomy and planetary sciences have substantial impact on the state's economy.
Provided by AASTA
South America and Antarctica
January 18, 2008
On Tuesday, January 15th, the Arizona Arts, Sciences, and Technology Academy (AASTA) released an impact report of astronomy, planetary sciences and space sciences (APSS) on Arizona's economy.

The report found that research in APSS in 2006 alone pumped over $250 million into Arizona's economy. By comparison, this is equivalent to the economic impact of the Super Bowl every 2 years. As a traditional resource for Arizona, APSS have long been relied upon as a stable economic contributor to the state; regardless of the economic environment, APSS research has always been lucrative.

The study also found that there are multiple threats to these fields that will diminish the economic contributions if immediate and decisive action is not taken. Recommendations made by the report include creating a plan for the future of research in APSS, increasing federal funding, developing and exploiting technologies within the established infrastructure, such as the state universities, and working with state and local policymakers to protect APSS resources, including setting new measures to control light pollution.

"Arizona has always been a leader in astronomy, planetary sciences, and space sciences and this report illustrates just how much of an impact research in these fields has on Arizona," says Patrick Burkhart, president of APSS. "It is imperative that the state takes up these recommendations so that we can continue to bring in funding and help our economy grow during this downturn."
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Lucimary Vargas
Além Paraíba-MG-Brasil

MESSENGER at Mercury

For the first time in more than 30 years, a spacecraft will return to Mercury, providing images from sections of the planet that have never been viewed by a spacecraft.
Provided by the Johns Hopkins University
This visible-infrared image shows an incoming view of Mercury, about 80 minutes before MESSENGER's closest pass of the planet on January 14, 2008, from a distance of about 27,000 kilometers (17,000 miles). NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington [View Larger Image]
Updated January 22, 2008
One week ago, the MESSENGER spacecraft transmitted to Earth the first high-resolution image of Mercury by a spacecraft in over 30 years, since the three Mercury flybys of Mariner 10 in 1974 and 1975. MESSENGER's Wide Angle Camera (WAC), part of the Mercury Dual Imaging System (MDIS), is equipped with 11 narrow-band color filters, in contrast to the two visible-light filters and one ultraviolet filter that were on Mariner 10's vidicon camera. By combining images taken through different filters in the visible and infrared, the MESSENGER data allow Mercury to be seen in a variety of high-resolution color views not previously possible. MESSENGER's eyes can see far beyond the color range of the human eye, and the colors seen in the accompanying image are somewhat different from what a human would see.

The color image was generated by combining three separate images taken through WAC filters sensitive to light in different wavelengths; filters that transmit light with wavelengths of 1000, 700, and 430 nanometers (infrared, far red, and violet, respectively) were placed in the red, green, and blue channels, respectively, to create this image. The human eye is sensitive across only the wavelength range 400 to 700 nanometers. Creating a false-color image in this way accentuates color differences on Mercury's surface that cannot be seen in the single-filter, black-and-white image released last week.

Image sequences acquired through the 11 different MDIS filters are being used to distinguish subtle color variations indicative of different rock types. By analyzing color differences across all 11 filters, the MESSENGER team is investigating the variety of mineral and rock types present on Mercury's surface. Such information will be key to addressing fundamental questions about how Mercury formed and evolved.

Mercury has a diameter of about 3030 miles (4880 kilometers), and the smallest feature visible in this color image is about 6 miles (10 kilometers) in size.
This image was acquired about 98 minutes after MESSENGER's closest approach to Mercury, when the spacecraft was at a distance of about 21,000 miles (33,000 kilometers). NASA/JHUAPL/CWI [View Larger Image]
Updated January 21, 2008
One week ago, on January 14, 2008, MESSENGER passed 124 miles (200 kilometers) above the surface of Mercury and snapped the first pictures of a side of Mercury not previously seen by a spacecraft. The image to the right shows that previously unseen side, with a view looking toward Mercury's south pole. The southern limb of the planet can be seen in the bottom right of the image. The bottom left of the image shows the transition from the sunlit, day side of Mercury to the dark, night side of the planet, a transition line known as the terminator. In the region near the terminator, the sun shines on the surface at a low angle, causing the rims of craters and other elevated surface features to cast long shadows, accentuating height differences in the image.

This image is just one in a planned sequence of 42 images acquired by the Narrow Angle Camera of the Mercury Dual Imaging System (MDIS). From these 42 images, the MESSENGER team is creating a high-resolution mosaic image of this previously unseen portion of Mercury. During the flyby, MDIS took more than 1,200 images, which are being combined to create multiple mosaics with different resolutions and of different portions of the planet. The creation of high-resolution mosaic images will enable a global view of Mercury's surface and will be used to understand the geologic processes that made Mercury the planet we see today.
This picture provides a global context for the MDIS Narrow Angle Camera (NAC) images taken while MESSENGER was inbound. This image was taken about 80 minutes before closest approach from a distance of about 17,000 miles (27,000 kilometers) and shows features as small as 6 miles (10 kilometers). NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington [View Larger Image]
Updated January 18, 2008
As MESSENGER neared Mercury on January 14, 2008, the spacecraft's Wide Angle Camera on the Mercury Dual Imaging System (MDIS) took images of the planet through each of its 11 filters. This image of the planet's full crescent was taken using the 7th filter, in light near the far-red end of the visible spectrum (750 nm). The image shows portions of Mercury previously seen by Mariner 10, but when Mariner 10 flew by the planet at each of its encounters the Sun was nearly overhead. For this MESSENGER flyby, in contrast, the Sun is shining obliquely on regions near the day/night boundary (called the terminator) on the right-hand side of the crescent, revealing the surface topography in sharp relief. This image illustrates how MESSENGER, during its future flybys and subsequent orbital mission, will teach us much about the portion of Mercury already imaged by Mariner 10, and not just because of its superior camera and close proximity to the planet. The solar lighting geometry makes an enormous difference.

A day after its successful flyby of Mercury, the MESSENGER spacecraft turned toward Earth on Tuesday and began downloading the 500 megabytes of data that had been stored on the solid-state recorder during the encounter. All of those data, including 1,213 images from the Mercury Dual Imaging System (MDIS) cameras, have now been received by the Science Operations Center at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. Preliminary analysis of these data by the MESSENGER Science Team has confirmed that all seven MESSENGER instruments are healthy and operated as planned during the flyby.

As MESSENGER flew by the planet, it missed its targeted aim point by only 5.12 miles (8.25 kilometers), affording the critical gravity assist needed to continue on a course to become, in 2011, the first spacecraft ever to orbit Mercury. During this first encounter, the payload successfully conducted a carefully orchestrated sequence of observations designed to take full advantage of the geometry of the flyby trajectory and to optimize the science return from each instrument.

In addition to images of the previously unseen portion of the planet's surface, measurements were made that will contribute to the characterization of all aspects of Mercury and its environment, from its metallic core to the far reaches of its magnetosphere. "We have one excited science team," says MESSENGER Project Manager, Peter D. Bedini, of APL, "and their enthusiasm is contagious."

The analysis of these data is just beginning, but there are already indications that new discoveries are at hand.
The image shows a variety of surface textures, including smooth plains at the center of the image, many impact craters (some with central peaks), and rough material that appears to have been ejected from the large crater to the lower right. NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington [View Larger Image]
Updated January 17, 2008
As the MESSENGER spacecraft drew closer to Mercury for its historic first flyby, the spacecraft's Narrow Angle Camera (NAC) on the Mercury Dual Imaging System (MDIS) acquired an image mosaic of the sunlit portion of the planet. This image is one of those mosaic frames and was acquired on January 14, 2008, when the spacecraft was about 11,000 miles (18,000 kilometers) from the surface of Mercury, about 55 minutes before MESSENGER's closest approach to the planet.

This large 120 miles (about 200 milometers) crater was seen in less detail by Mariner 10 more than 3 decades ago and was named Sholem Aleichem for the Yiddish writer. In this MESSENGER image, it can be seen that the plains deposits filling the crater's interior have been deformed by linear ridges. The shadowed area on the right of the image is the day-night boundary, known as the terminator. Altogether, MESSENGER acquired over 1200 images of Mercury, which the science team members are now examining in detail to learn about the history and evolution of the innermost planet.
This MESSENGER image was taken from a distance of about 11,000 miles (18,000 kilometers), about 56 minutes before the spacecraft's closest encounter with Mercury. It shows a region roughly 300 miles (500 km) across, and craters as small as 0.6 mile (1 km) can be seen in the image above. NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington [View Larger Image]
Updated January 16, 2008
As MESSENGER approached Mercury on January 14, 2008, the spacecraft's Narrow-Angle Camera on the Mercury Dual Imaging System (MDIS) instrument captured this view of the planet's rugged, cratered landscape illuminated obliquely by the Sun. The large, shadow-filled, double ringed crater to the upper right was glimpsed by Mariner 10 more than three decades ago and named Vivaldi, after the Italian composer. Its outer ring has a diameter of about about 125 miles (200 kilometers). MESSENGER's modern camera has revealed detail that was not well seen by Mariner 10, including the broad ancient depression overlapped by the lower-left part of the Vivaldi crater. The MESSENGER science team is in the process of evaluating later images snapped from even closer range showing features on the side of Mercury never seen by Mariner 10. It is already clear that MESSENGER's superior camera will tell us much that could not be resolved even on the side of Mercury viewed by Mariner's vidicon camera in the mid-1970s.
The MESSENGER spacecraft snapped this image yesterday morning from a distance of 470,000 miles (760,000 km). The image has a resolution of about 12 miles (20 km) per pixel. NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington [View Larger Image]
Updated January 14, 2008
NASA's MESSENGER spacecraft is on track for its first flyby of Mercury today. The craft will explore the planet from as close as 125 miles (200 kilometers).

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) craft, launched August 3, 2004, will be the first spacecraft to study the innermost planet while in orbit around it. Following three flybys during the next 3 years, MESSENGER will reach orbit around Mercury in 2011.

Planetary scientists are eager to get a closer look at the Sun's nearest neighbor.

"We are about to visit Mercury for the first time in more than 30 years, and we can't wait," says MESSENGER principal investigator Sean Solomon of the Carnegie Institution of Washington.

NASA's Mariner 10 is the only other spacecraft to visit the planet closest to the Sun.

"We'll be making close-in observations of the composition of Mercury's surface and atmosphere, and we'll be probing deeper into the planet's magnetosphere than we've ever been," says Solomon.

The MESSENGER probe's Mercury Dual Imaging System cameras began snapping pictures of the planet January 9. NASA plans a mission update on the Mercury flyby January 30.

Visit MESSENGER's online newsroom.
January 8, 2008
On January 9, MESSENGER's Mercury Dual Imaging System cameras began gathering pictures of Mercury as the probe zeros in on the planet.

"With just one week to go before the flyby, the spacecraft is on target to encounter the planet at an altitude of 202 kilometers," says Mission Systems Engineer Eric Finnegan of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. "All subsystems and instruments are operating nominally and configured for the start of the flyby sequence, except for the Mercury Laser Altimeter and part of the Gamma-Ray Spectrometer, which we'll turn on just before the flyby."

Over the next week, the team will make final flyby preparations and upload the final command sequences for the encounter.

"We are about to visit Mercury for the first time in more than 30 years, and we can't wait," says MESSENGER Principal Investigator Sean Solomon of the Carnegie Institution of Washington. "In addition to providing the critical gravity assist that will move MESSENGER along its path toward Mercury orbit insertion in March 2011, this flyby will let us see parts of Mercury never before viewed by spacecraft. We'll be making close-in observations of the composition of Mercury's surface and atmosphere, and we'll be probing deeper into the planet's magnetosphere than we've ever been. We expect many surprises."

On December 19th, MESSENGER's 19th trajectory correction maneuver (TCM-19) changed the spacecraft's velocity by 3.6 feet per second (1.1 meters per second), directing MESSENGER closer to its intended target for the first flyby. TCM-19 went so well that the mission design and navigation teams have decided that a TCM scheduled for January 10 will not be needed.

"Cancellation of this maneuver is a demonstration of the near-perfect execution of TCM-19 just prior to the start of the holiday season," says Finnegan.
Experience MESSENGER's Mercury flyby virtually
Artist rendition of MESSENGER
Planetary scientists have sent the MESSENGER space probe to Mercury to answer questions left hanging after the visit of the last spacecraft, Mariner 10, in the mid-1970s. NASA / JHUAPL / CIW [View Larger Image]

See Mercury through the "eyes" of MESSENGER's imagers with the Mercury Flyby Visualization Tool. This new web feature offers a unique opportunity to see simulated views of Mercury from MESSENGER's perspective during approach, flyby, and departure, or in real-time (as the observations actually occur).

This tool combines the best available image map of Mercury's surface with observation sequences for the Mercury Dual Imaging System (MDIS), Mercury Atmospheric and Surface Composition Spectrometer (MASCS), and Mercury Laser Altimeter (MLA). The map of Mercury's surface combines Earth-based low-resolution radar images from the Arecibo Observatory in Puerto Rico and image mosaics from the Mariner 10 spacecraft flybys of Mercury in 1974 and 1975.

Lucimary Vargas de Oliveira Guardamino Espinoza
Além Paraíba-MG-Brasil
Observatório Astronômico Monoceros
Estacão Meteorológica Nº083/5ºDISME-INMET
CEPESLE -Centro de Estudos e Pesquisas Sertões do Leste
AHAP-Arquivo Histórico de Além Paraíba
MSN: observatoriomonoceros@hotmail.com

Venus meets Jupiter

On February 1, the solar system's brightest planets appear closest together.
Francis Reddy
Jupiter joined Venus
Jupiter joined Venus (left) for an early morning rendezvous in November 2004. Here, the pair gleams over Bursa and Uludag, Turkey, before dawn. A similar sight awaits early risers throughout late January and early February. Tunç Tezel [View Larger Image]
Updated January 22, 2008
Venus, the planet nearest to Earth, and Jupiter, the solar system's biggest world, are headed for a morning meeting. As the brightest planets in the sky, the pair makes a conspicuous sight in eastern twilight.

During the next week, watch Jupiter edge ever closer to Venus. As the planets draw together, they'll begin to resemble a pair of celestial headlights - an appropriate comparison for an event that graces the morning commute.

The planetary dance culminates February 1, when the two worlds lie a little more than one Moon-width apart. That's so close, observers with telescopes can view both planets at the same time by using low-power, wide-field eyepieces. What's more, Jupiter's four biggest moons will be on display as well. Observers can take in six worlds with one view.

Although the two planets seem to be in danger of colliding, appearances can be deceiving. On February 1, Jupiter lies 562 million miles (904 million kilometers) away. That's more than 4.5 times farther than Venus, which is 124 million miles (200 million km) distant the same morning.

Even so, a telescope will show Jupiter's 33" width is nearly 3 times the size of Venus' disk. The reason, of course, is that giant Jupiter, the solar system's largest planet, is 12 times Venus' size.
How you can see it
From January 25 and February 1, look low in the southeast in the hour before dawn. The two brightest star-like objects are Venus and Jupiter. Venus is the brighter of the two.
Venus and Jupiter

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Lucimary Vargas
Além Paraíba-MG-Brasil

Probe's encounter reveals unseen side of Mercury


Posted: January 16, 2008

Two days after NASA's Messenger probe sped past Mercury, a group of Earth-bound scientists are getting their first glimpse of previously undiscovered parts of the scorched planet.

Messenger provides the first look at Mercury's previously unseen side. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Scientists at the Johns Hopkins University's Applied Physics Laboratory reported Messenger's wide- and narrow-angle cameras snapped 1,213 images during about 55 hours of near-continuous science observations.

Four images were posted on the mission's Web site by late Wednesday, including shots of never-before-seen portions of the solar system's innermost planet.

It could take up to a week for all of the 700 gigabytes of data to be sent home. All of the probe's scientific instruments were turned on for the trip past Mercury to study its composition and terrain.

Officials also plan to create at least seven large mosaic images of the desolate world from high-resolution snapshots taken by Messenger's narrow-angle camera in the coming weeks.

Monday's historic fly-by was the first time a robotic spacecraft visited the hostile world since NASA's Mariner 10 probe zoomed past Mercury nearly 33 years ago. Mariner 10 approached Mercury three times during its mission but never entered orbit.

This image shows a previously unseen crater with distinctive bright rays of ejected material extending radially outward from the crater's center. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
But Mariner 10 was only able to study about 45 percent of Mercury's surface, and Messenger was dispatched to fill in the voids from the first round of the planet's exploration three decades ago. Messenger's camera system was able to see about half of the unexplored side of Mercury on Monday.

The highest resolution images from Monday are also giving scientists a more detailed view of known surface features, including a giant 800-mile-wide impact basin named Caloris.

"It is already clear that MESSENGER's superior camera will tell us much that could not be resolved even on the side of Mercury viewed by Mariner's vidicon camera in the mid-1970s," the science team said in a written statement.

The Caloris basin, believed to be one of the youngest large impact craters in the solar system, lied in partial darkness during the Mariner 10 mission.

"The new image shows the complete basin interior and reveals that it is brighter than the surrounding regions and may therefore have a different composition," the science team said.

Messenger's modern camera has revealed detail that was not well seen by Mariner 10, including the broad ancient depression overlapped by the lower-left part of the Vivaldi crater. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Messenger flew within 124 miles of Mercury's singed surface at 2:04 p.m. EST Monday as part of a pinball-like course through the inner solar system to set up for the craft's permanent arrival at Mercury.

Messenger already completed swings past Earth and Venus since its 2004 launch. Two more close approaches to Mercury are planned in October and September 2009 to slow the spacecraft before it maneuvers into orbit around the planet on March 18, 2011.

Scientists plan to operate Messenger for at least a year after its 2011 arrival in an effort to answer key questions about the planet's history and the formation of the inner solar system.

One of the highest and longest scarps (cliffs) yet seen on Mercury curves from the top center down across the right side of this image. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

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Lucimary Vargas
Além Paraíba-MG-Brasil


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