Posted on by Mark Mortimer

Book Review: Leaving Earth

The Soviet Union began by vouching for human habitation once they had lost the race to the moon. Patsayev, Dobrovolsky and Volkov occupied the first Salyut which was the first manned orbital space station. During their three weeks in this small metal tube like craft they kept busy with adapting to a climate and facility created by ground-based designers who had no real appreciation of weightlessness. These cosmonauts succeeded in performing nonetheless with one highlight being the growth of many plants from a variety of seeds. By sticking to a rigid and very busy schedule of work, exercise and maintenance, they added significant insight into living in space for long durations. Sadly though this didn’t come freely for the Soviet Union as the cosmonauts tragically died while descending in their re-entry capsule.

Skylab was the USA’s response to Salyut. This behemoth, launched via the last Saturn V rocket system, provided over 12700 cubic feet of living space. This was a veritable mansion as compared to the Soviet Union’s Salyut. Here Conrad, Kerwin and Weitz completed a four week tour that was as much for repair and reconstruction as it was for scientific experiments. In a ‘we can fix anything’ mentality, they unstuck a solar panel, unpacked equipment and set up experiments. Surprisingly, they experienced no space sickness, just like the first Soviets, though this turned out
to be very rare.

In Salyut 4 Grechko and Gubarev, had brought seeds, amoebas, tadpoles, fish and flies to share their living quarters in Salyut 4. After 30 days of scientific experiments, observation and maintenance activity, they successfully returned to Earth. This was the Soviet Union’s first success in manned station return. With Salyut 6 the Soviet Union launched over eighteen different manned missions during its almost five years of operation. Residents stayed for over six months with a complement, at times, of up to four people. The Salyut 7 and Mir missions built upon the Soviet Union’s successes. Space flight durations were extended. Equipment was better designed, while experiments provided more insight on how the human body reacts to extended times in space. The cosmonauts learned to focus and control their emotions to stay mentally and emotionally fit in such an unnatural situation. They could repair aged or broken equipment, recover from unexpected failures and add significant structural components. This time saw amazing progress but the end of the Soviet Union also spelt the end for Salyut’s and Mir’s roles of being stars for communism.

Nevertheless, political expediency still is keeping the space program alive. Russia deorbited Mir to save money. They then joined with the USA and other nations to pursue construction of the International Space Station (ISS). Though Russia was able to impart some of their hard earned knowledge the USA considered the contribution to be more a form of economic relief for the newly recreated state. From this it appears the political climates have almost changed places as the Russian space program, by necessity, is relying on capitalism for its very survival while the NASA bureaucracy appears to be more interested in keeping itself alive than in advancing the space program. Yet the ISS is in space and is contributing to our knowledge.

Though this book contains many of the technical issues of the designs of space stations as well as the sordid details of politics, its greatest provision is the human experiences that so richly embellish the story. You read of cosmonauts that try farming plants throughout the interior of their craft in efforts to yield a worthwhile harvest. There is a female fighter pilot/cosmonaut that ended up wearing a dress and being a hostess in space. Innumerable misses of docking craft demonstrate the riskiness of the whole affair. As well, the complete dependency on temperamental machinery constantly kept stark terror a scant distance away. Most of all though, the reader can see the triumph of human ingenuity and community where coming together is not just a convenience but a necessity.

There are many people who believe that Mars is the next step for the human race. Robert Zimmerman shares in the belief and in his book Leaving Earth he shows how the previous thirty years have given humankind an incredible wealth of knowledge on how to do this. Within it are many excellent descriptions of good designs and bad designs, heroic actions to save a mission and errors in judgement that nearly doom them. Yet the message comes through again and again, if we want to go to Mars we have shown we have the ability, we only need the will.

To read more reviews, or order the book online, visit Amazon.com.

Review by Mark Mortimer

Posted on by Fraser Cain

Mars Rover Tracks Spotted From Space

NASA’s Mars Global Surveyor, starting its third mission extension this week after seven years of orbiting Mars, is using an innovative technique to capture pictures even sharper than most of the more than 170,000 it has already produced.

One dramatic example from the spacecraft’s Mars Orbiter Camera shows wheel tracks of NASA’s Mars Exploration Rover Spirit and the rover itself. Another tells scientists that no boulders bigger than about 1 to 2 meters (3 to 7 feet) are exposed in giant ripples created by a catastrophic flood.

Those examples are available online at http://www.msss.com/mars_images/moc/2004/09/27/ and http://mars.jpl.nasa.gov/mgs. In addition, about 24,000 newly catalogued images that Mars Global Surveyor took between October 2003 and March 2004 have been added to the Mars Orbiter Camera Image Gallery at http://www.msss.com/moc_gallery/. These include additional pictures of the Mars Exploration Rover sites seen from orbit.

“Over the past year and a half, the camera and spacecraft teams for Mars Global Surveyor have worked together to develop a technique that allows us to roll the entire spacecraft so that the camera can be scanned in a way that sees details at three times higher resolution than we normally get,” said Dr. Ken Edgett, staff scientist for Malin Space Science Systems, San Diego, Calif., which built and operates the Mars Orbiter Camera. The technique adjusts the rotation rate of the spacecraft to match the ground speed under the camera.

“The image motion compensation is tricky and the spacecraft does not always hit its target. However, when it does, the results can be spectacular,” Edgett said.

The Mars Orbiter Camera acquires the highest resolution images ever obtained from a Mars-orbiting spacecraft. During normal operating conditions, the smallest objects that can be resolved on the martian surface in these images are about 4 to 5 meters (13 to 16 feet) across. With the adjusted-rotation technique, called “compensated pitch and roll targeted observation,” objects as small as 1.5 meters (4.9 feet) can be seen in images from the same camera. Resolution capability of 1.4 meters (4.6 feet) per pixel is improved to one-half meter (1.6 feet) per pixel. Because the maneuvers are complex and the amount of data that can be acquired is limited, most images from the camera are still taken without using that technique.

Mars Global Surveyor began orbiting Mars on Sept. 12, 1997. After gradually adjusting the shape of its orbit, it began systematically mapping the planet in March 1999. The Mars Orbiter Camera’s narrow-angle camera has now examined nearly 4.5 percent of Mars’ surface, including extensive imaging of candidate and selected landing sites for surface missions. The Mars Orbiter Camera also includes a wide-angle camera that observes the entire planet daily.

“Mars Global Surveyor has been productive longer than any other spacecraft ever sent to Mars, since it surpassed Viking Lander 1’s longevity earlier this year and has returned more images than all past Mars missions combined,” said Tom Thorpe, project manager for Mars Global Surveyor at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. The mission will complete its 25,000th mapping orbit on Oct. 11.

Principal goals for the orbiter’s latest mission extension, beginning Oct. 1, include continued weather monitoring to form a continuous set of observations with NASA’s next Mars mission, Mars Reconnaissance Orbiter, scheduled to reach the red planet in 2006; imaging of possible landing sites for the Phoenix 2007 Mars Scout lander and 2009 Mars Science Laboratory rover; continued mapping and analysis of key sedimentary-rock outcrop sites; and continued monitoring of changes on the surface due to wind and ice. Because the narrow-angle camera has imaged only a small fraction of the surface, new discoveries about surface features are likely to come at any time. The extension runs two years, through September 2006, with a budget of $7.5 million per year.

Dr. James Garvin, NASA’s chief scientist for Mars and the Moon, said, “Mars Global Surveyor continues to catalyze new science as it explores Mars at scales compatible with those that our Mars Exploration Rovers negotiate every day, and its extended mission will continue to set the stage for upcoming observations by the Mars Reconnaissance Orbiter.”

Additional information about Mars Global Surveyor is available online at: http://mars.jpl.nasa.gov/mgs/. In addition to semi-annual releases of large collections of archived pictures, the Mars Orbiter Camera team posts a new image daily and last year began soliciting public suggestions for camera targets on Mars. These materials can be viewed online at http://www.msss.com . For more information about NASA and other space science programs on the Internet, visit http://www.nasa.gov.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Global Surveyor mission for NASA’s Science Mission Directorate, Washington, D.C. JPL’s industrial partner is Lockheed Martin Space Systems, Denver, which built and operates the spacecraft.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Here Come The Thirty Metre Telescopes

Thirty Metre Optical and Infrared ground-based telescopes should be seeing first light in about 2011, and be fully operational by 2015. Four such instruments are in the works, CalTech?s TMT, Gemini?s GSMT, Canada?s VLOT, and Europe?s ELT. With 100 times the speed of Hubble, and three times the resolution of the Keck instruments, these tools will help unlock some new keys to our understanding the cosmos.

Earth-based thirty-metre telescopes are being funded, and designed now. Caltech’s TMT project will undergo design reviews in 2006 and 2007 with full construction funding scheduled to be given by the Gordon and Betty Moore Foundation in July 2008. Gordon Moore [of Moore?s Law fame] was the founder of Intel. His foundation supplied a 17 million dollar grant to design the TMT in October 2003. In total the instrument is expected to cost about 800 million dollars.

Adaptive optics have proved a tremendous success, and are one reason that there will be no replacement for the Hubble telescope as a space based tool for covering the optical and near infrared part of the spectrum. These three instruments will be getting first light with some segments about the same time that the 6.5 metre James Webb Space Telescope will begin its science mission in 2011-2.

Robert Gilmozzi?s OverWhelmingly Large Telescope [OWL project] is also trying to get first light by 2015, but faces more financial and technical obstacles than the 30-meter instruments. If the OWL doesn?t get built in this go-around, similar designs will likely be used for the following decade.

These instruments will be able to perform many tasks that the current generation of instruments either can?t do, or would require prohibitive amounts of observing time to accomplish including the following:

  • Map the density and heavy element content of the intergalactic media from nearby to beyond z=1.5 by measuring the details absorption spectra of 100,000 QSOs.
  • Observe the galaxy formation process by studying the movement of ionized gas clouds from z=3 to 8. Note these instruments can discern sources as close as 150 parsecs apart at z=3.
  • Chart the distortion of images of background galaxies when looking through galactic clusters to map the presence of dark matter to an unprecedented level of detail.
  • Chart the star populations of nearby galaxies observing element abundances, and determining formation histories.
  • Observe planet formation around the nearest thousand new stars. This instrument will be able to resolve to 0.4AU when looking at objects 33 light-years away.
  • Detect and characterize mature planets around nearby stars.

Caltech just put up a job posting for an Observatory Scientist for the TMT project. The Thirty metre telescopes are on their way.

Written by John A. Cross

Posted on by Fraser Cain

Toutatis Sneaks Past the Earth on Wednesday

Early Wednesday morning, a 5,500 million pound asteroid measuring 5 kilometers in length will pass very close to Earth.

An asteroid two to three times that diameter is credited with causing the extinction of 85 percent of the world’s species, including the dinosaurs, when it hit our planet 65 million years ago.

Luckily for us, asteroid Toutatis is only a tourist, and doesn’t plan to stop here. It will come within 1.5 million kilometers (960,000 miles) of Earth, or four times the Earth-moon distance. Toutatis is the largest asteroid to come that close in more than a century.

Many smaller asteroids often pass well inside the moon’s orbit. The Earth is also hit continually with tiny meteors that often become “shooting stars” as they harmlessly burn up in the atmosphere.

But if a rock the size of Toutatis hit, the atmosphere would do little more than slow it down a bit before it slammed to Earth. The impact would create a vast crater, and toss so much dust and vaporized minerals into the air the skies would darken. Seismic waves created by the explosion would generate tsunamis and earthquakes, and red-hot rocks falling back to Earth would ignite forest fires.

Toutatis, also known as asteroid 4179, is 4.6 kilometers (2.9 miles) long and 2.4 kilometers (1.5 miles) wide. Although Toutatis looks like a large peanut, radar images revealed it is actually composed of two rocks that are in close contact. One of the rocks is approximately twice as large as the other.

Toutatis has a strange rotation –instead of the spinning on a single axis, like the planets and most other asteroids do, Toutatis tumbles so erratically that its orientation with respect to the solar system never repeats.

“The vast majority of asteroids, and all the planets, spin about a single axis, like a football thrown in a perfect spiral,” says Scott Hudson of Washington State University, “but Toutatis tumbles like a flubbed pass.”

Toutatis’s four-year orbit around the sun is also eccentric, extending from just inside the Earth’s orbit to the main asteroid belt between Mars and Jupiter.

Astronomer Christian Pollas discovered Toutatis on January 4, 1989. Pollas spotted the asteroid on photographic plates taken by Alain Maury and Derral Mulholland, who had taken the photos while observing Jupiter’s satellites.

Toutatis flew close by Earth in 1992 and 1996, but it hasn’t come this near to us since 1353. The next time it will pass this close again will be in the year 2562. The asteroid’s orbit around the sun is so eccentric that it can’t be predicted with much certainty for more than a few hundred years in the future. Since researchers can’t say Toutatis will never hit Earth, it is currently listed as a Potentially Hazardous Asteroid.

There is a rumor circulating on the Internet that the asteroid will strike Earth during this 2004 flyby. However, astronomers have been tracking the path of Toutatis ever since it was discovered, and they are certain it will pass safely by Earth.

Throughout history, several asteroids have hit Earth. The solar system was cluttered with asteroids while the Earth was young, and the face of the moon and other dead planetary bodies shows how frequent such impacts were. Impacts by large rocks are much less frequent today, but they can still occur.

There are thought to be more than 300,000 nearby small asteroids (asteroids about 100 meters across). Such asteroids should statistically hit Earth once every few thousand years. The most recent such asteroid strike occurred in 1908, when an asteroid measuring about 60 meters in diameter hit Russia. The “Tunguska” bolide exploded in the atmosphere and flattened about 700 square miles of Siberian forest.

Large (1 kilometer or greater) asteroids are far more rare and infrequent. There are only about 1,100 nearby large asteroids, and they are predicted to strike the Earth every half million years or so. But when these asteroids strike, they can cause catastrophic changes in the global climate. Asteroids that cause mass extinctions are thought to be 10 kilometers or greater in diameter.

The Spaceguard Survey was established to track large asteroids and comets that might pose a direct threat to Earth. So far, the Spaceguard Survey has found about half of these NEOs, and they expect to find the majority of them by 2008.

Although Toutatis will be in the far southern sky when it is closest to Earth, the asteroid is expected to brighten a few days prior to a 10th magnitude point of light visible from the Northern Hemisphere. Sky-watchers should look for it near the bright star Delta Capricorni.

Toutatis won’t be visible to the naked eye, but binoculars should suffice for spotting it in the night sky. A telescope would provide the best viewing, because it would allow the viewer to detect the slow motion of Toutatis against the background stars.

Original Source: Astrobiology Magazine Article

Posted on by Fraser Cain

How Mars Could Be Losing Its Water

Image credit: ESA
Recent results from the ASPERA-3 instrument on board Mars Express confirm that a very efficient process is at work in the Martian atmosphere which could explain the loss of water. Water is believed to have once been abundant on the Red Planet. Professor Rickard Lundin, leader of the ASPERA-3 team, describes these findings in a paper published in the latest issue of ?Science?.

Mars is bombarded by a flood of charged particles from the Sun, commonly called the ?solar wind? and consisting of electrons and alpha particles. The solar wind erodes the atmosphere of Mars, and is believed to have stripped away a large amount of water that was present on the planet about 3.8 billion years ago. Geological evidence, as recently confirmed by images from the High Resolution Stereo Camera (HRSC) onboard Mars Express, indicates that water flows and even an ocean in the Northern hemisphere shaped the surface of Mars.

Today, water still exists on the Red Planet, but less than in the past. Observations made earlier this year by the OMEGA instrument on Mars Express showed that Mars has vast fields of perennial water ice, stretching out from its south pole.

The ASPERA-3 instrument on board Mars Express aims to answer the question of whether the solar wind interaction with the upper atmosphere of Mars contributes to the depletion of water. It is measuring a process called ?solar wind scavenging?, or the slow ?invisible? escape of volatile gases and liquid compounds which make up the atmosphere and hydrosphere of a planet. Using plasma spectrometers and a special imager to detect energetic neutral atoms, ASPERA-3 is making global and simultaneous measurements of the solar wind, the inflow of energetic particles, and also the ?planetary wind?, which is the outflow of particles from the Martian atmosphere and ionosphere.

Aspera 3 has established that the solar wind penetrates through the ionosphere and very deeply into the Martian atmosphere down to an altitude of 270 kilometres. This seems to be the reason for the acceleration processes that cause the loss of atmosphere on Mars.

Original Source: ESA News Release

Posted on by Fraser Cain

Da Vinci Project Pushes Back Launch

The Golden Palace.com Space Program Powered by the da Vinci Project announced that it has revised its October 2nd planned flight to space in pursuit of the Ansari X PRIZE.

Contributing factors to this revision were availability of a few key components and their integration into the overall space flight program. The Project will provide public notice of its intended flights as soon as practicable under the auspices of the Ansari X PRIZE, notwithstanding the flight plans of any other competitor.

?The flight insurance for the 2 launches has been secured?, says Brian Feeney, Project Leader. ?We?re still a go for launch. We?ve made milestone progress since the early August arrival of our title sponsor, Golden Palace.com and we intend to prove that Canadians can and will put a man into space?.

About The Golden Palace.com Space Program Powered by the da Vinci Project (www.davinciproject.com)
The Golden Palace.com Space Program Powered by the da Vinci Project’s aim of capturing the Ansari X PRIZE, the international “New Race to Space(R)” is backed by a core of volunteers from many walks of life and disciplines. Aerospace engineers, experts in project management and finance contribute their time and expertise towards the realization of the next step in Human discovery. The Project’s novel rocket design will be launched from the world’s largest reusable helium balloon at an altitude of 80,000 feet (24,400 meters). To learn more, visit www.davinciproject.com.

About the ANSARI X PRIZE Competition
In order to win the ANSARI X PRIZE, teams must build a safe/reusable space vehicle able to carry one pilot and the weight equivalent of two passengers 100km (62 miles) into sub-orbital space. The vehicle must be privately financed and safely launched twice within a two-week period. The first registered ANSARI X PRIZE team to complete this feat will win the $10 million prize and spectacular trophy.

About the X PRIZE Foundation (www.xprize.org)
The X PRIZE Foundation is a not-for-profit educational organization, with headquarters in St. Louis, Missouri. The Foundation?s ANSARI X PRIZE Competition is supported by its Title Sponsor the Ansari family and its Presenting Sponsor Champ Car World Series. The Foundation is also supported by private donations from the St. Louis Community through the New Spirit of St. Louis Organization. The Foundation’s mission is to educate the public about space travel, create educational programming for students and space enthusiasts, and provide incentives in the private sector to make space travel frequent and affordable for the general public. Several additional sponsorships for the ANSARI X PRIZE competition remain available to corporations or individuals who wish to support the contest and associate themselves with courage, determination, achievement, space, speed, high performance and technology.

Original Source: da Vinci Project News Release

Posted on by Fraser Cain

First Genesis Samples Shipped Out

The Genesis team has shipped its first scientific sample from the mission’s specially constructed cleanroom at the U.S. Army Proving Ground in Dugway, Utah. The sample, containing what are known as “lid foils,” was attached to the interior lid of the Genesis sample return capsule.

“This is the first batch in what we are growing more confident will be many more scientifically valuable samples,” said Genesis Project Manager Don Sweetnam of NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “It appears that we have recovered about 75 to 80 percent of these lid foils. A great deal of credit has to go to the dedicated men and women of Genesis who continue to do very precise, detailed work out there in the Utah desert.”

After the sample was shipped from Utah, it was received by Genesis co-investigator Nishiizumi Kunihiko from the University of California, Berkeley, Space Sciences Laboratory.

In addition to the lid foils, there was optimistic news about the collector array. Team members from JPL arrived in Utah on Monday with a special fixture to aid in handling the science canister’s stack of four collector arrays. The stack was successfully removed as one piece. With the stack on the fixture, the team has begun the process of disassembling the arrays. Several large pieces of individual collector materials, including one completely intact hexagon, were recovered from the top array.

The Genesis cleanroom activities are focused on getting the materials ready for shipping. A date has not yet been selected for transporting the Genesis science canister and recovered collector materials from Dugway to NASA’s Johnson Space Center in Houston. The team continues its meticulous work and believes that a significant repository of solar wind materials has survived that will keep the science community busy working on their science objectives.

News and information about Genesis is available online at http://www.nasa.gov/genesis. For background information about Genesis, visit http://genesismission.jpl.nasa.gov. For information about NASA visit http://www.nasa.gov.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Biggest Collision in the Universe

With ESA?s XMM-Newton observatory, an international team of scientists has observed a nearby head-on collision of two galaxy clusters that has smashed together thousands of galaxies and millions upon millions of stars. It is one of the most powerful events ever witnessed. Such collisions are second only to the Big Bang in total energy output.

The event details what the scientists are calling the ?perfect cosmic storm?: galaxy clusters that collided like two high-pressure weather fronts and created hurricane-like conditions, tossing galaxies far from their paths and churning shock waves of 100-million-degree gas through intergalactic space.

This unprecedented view of a merger in action crystallises the theory that the Universe built its magnificent hierarchal structure from the ?bottom up? – essentially through mergers of smaller galaxies and galaxy clusters into bigger ones.

“Here before our eyes we see the making of one of the biggest objects in the Universe,” said Dr Patrick Henry of the University of Hawaii, who led the study. “What was once two distinct but smaller galaxy clusters 300 million years ago is now one massive cluster in turmoil.?

Henry and his colleagues, Alexis Finoguenov and Ulrich Briel of the Max-Planck Institute for Extraterrestrial Physics in Germany, present these results in an upcoming issue of the Astrophysical Journal. The forecast for the new super-cluster, they said, is ‘clear and calm’ now that the worst of the storm has passed.

Galaxy clusters are the largest gravitationally bound structures in Universe, containing hundreds to thousands of galaxies. Our Milky Way galaxy is part of a small group of galaxies but is not gravitationally bound to the closest cluster, the Virgo Cluster. We are destined for a collision in a few thousand million years, though.

The cluster named Abell 754 in the constellation Hydra has been known for decades. However, to the scientists’ surprise, the new observation reveals that the merger may have occurred from the opposite direction than what was thought. They found evidence for this by tracing the wreckage today left in the merger’s wake, spanning a distance of millions of light years. While other large mergers are known, none has been measured in such detail as Abell 754.

For the first time, the scientists could create a complete ?weather map? of Abell 754 and thus determine a forecast. This map contains information about the temperature, pressure and density of the new cluster. As in all clusters, most the ordinary matter is in the form of gas between the galaxies and not locked up in the galaxies or stars themselves. The massive forces of the merging clusters accelerated intergalactic gas to great speeds. This resulted in shock waves that heat the gas to very high temperatures, which then radiated X-ray light, far more energetic than the visible light our eyes can detect. XMM-Newton, in orbit, detects this type of high-energy light.

The dynamics of the merger revealed by XMM-Newton point to a cluster in transition. “One cluster has apparently smashed into the other from the ‘north-west’ and has since made one pass through,” said Finoguenov. “Now, gravity will pull the remnants of this first cluster back towards the core of the second. Over the next few thousand million of years, the remnants of the clusters will settle and the merger will be complete.”

The observation implies that the largest structures in the Universe are essentially still forming in the modern era. Abell 754 is relatively close, about 800 million light years away. The construction boom may soon be over in a few more thousand million years though. A mysterious substance dubbed ‘dark energy’ appears to be accelerating the Universe’s expansion rate. This means that objects are flying apart from each other at an ever-increasing speed and that clusters may eventually never have the opportunity to collide with each other.

X-ray observations of galaxy clusters such as Abell 754 will help to better define dark energy and also dark matter, an ?invisible? and mysterious substance that appears to comprise over 80 percent of a galaxy cluster’s mass.

This observation was announced at a NASA Internet press conference today. A paper describing these results, by Patrick Henry and his collaborators, will be published in the Astrophysical Journal.

Original Source: ESA News Release

Posted on by Fraser Cain

Earliest Star Forming Galaxies Found

Detailed analyses of mankind’s deepest optical view of the universe, the Hubble Ultra Deep Field (HUDF), by several expert teams have at last identified what may turn out to be some of the earliest star-forming galaxies. Astronomers are now debating whether the hottest stars in these early galaxies may have provided enough radiation to “lift a curtain” of cold, primordial hydrogen that cooled after the big bang. This is a problem that has perplexed astronomers over the past decade, and NASA’s Hubble Space Telescope has at last glimpsed what could be the “end of the opening act” of galaxy formation. These faint sources illustrate how astronomers can begin to explore when the first galaxies formed and what their properties might be.

But even though Hubble has looked 95 percent of the way back to the beginning of time, astronomers agree that’s not far enough. “For the first time, we at last have real data to address this final frontier ? but we need more observations. We must push even deeper into the universe, unveiling what happened during the initial 5 percent of the remaining distance back to the big bang,” said Richard Ellis of the California Institute of Technology in Pasadena, Calif.

In the past couple decades astronomers have amassed evidence that we live in a reionized or “refried universe.” This so-called reionization epoch was a critical watershed for the evolving universe. During that early time cold hydrogen atoms drifting in space were pumped up with so much energy from the ultraviolet starlight that they were stripped of their electrons. The universe once again became transparent to light, like the Sun burning off a morning fog. This early period is called “reionization” because the primeval universe, which was hotter than our Sun, was initially ionized as a soup of hydrogen nuclei and free-moving electrons. As the universe cooled through the expansion of space, these electrons were captured by hydrogen nuclei to make neutral hydrogen. But the electrons were lost again when the first fiercely bright stars fired up.

The epoch of reionization is thought to have ended 0.5 to one billion years after the big bang. Constraints come from observations of quasars located with the Sloan Digital Sky Survey, and recent measures of polarization in the radiation emerging from the earliest phases of cosmic history recorded by the Wilkinson Microwave Anisotropy Probe (WMAP).

The major difficulty has been that galaxies at such a remote distance are very faint and are very hard to find. Only the most luminous galaxies can be relatively easily seen. Prior to the HUDF, astronomers did not have the sensitivity to accurately constrain the numbers of very distant sources at that epoch, and so there’s been a long-standing debate whether normal galaxies were really capable of doing the reionizing job.

The sensitivity of Hubble’s Advanced Camera for Surveys (ACS), combined with the penetrating power of the Near Infrared Camera and Multi-Object Spectrometer (NICMOS), finally revealed these long sough faint galaxies. The HUDF shows that close to a billion years after the big bang the early universe was filled with dwarf galaxies, but no fully formed galaxies like our Milky Way. After careful analysis, they have been sorted out as between 54 and 108 dim, red smudges sprinkled across the HUDF image. From a hierarchical point of view, this means the universe started out as a bunch of “mom & pop” stores, which merged into businesses, and then into giant corporations ? the majestic galaxies we see today.

HUDF research are being led by: Rodger Thompson (University of Arizona, Tucson, Ariz.) and collaborator Rychard Bouwens (University of California/Lick Observatory, Santa Cruz, Calif.) [see science papers 1, 2 and 3]; Haojing Yan (Spitzer Science Center, California Institute of Technology, Pasadena, Calif.) and Rogier Windhorst (Arizona State University, Tempe, Ariz.) [see science paper]; Massimo Stiavelli (Space Telescope Science Institute, Baltimore, MD.) [see science paper]; Andrew Bunker (University of Exeter and the University of Cambridge, UK) [see science papers 1 and 2]; and Sangeeta Malhotra and James Rhoads (Space Telescope Science Institute) [see science paper]. The teams used different techniques:

The Bunker team identified a list of 50 probable distant galaxies in the Ultra Deep Field and distributed details of their work within a day of the images becoming publicly available. They isolated their distant sample using techniques developed with earlier, less sensitive, Hubble images tested through spectroscopic observations undertaken with the 10-meter W.M. Keck observatory in Hawaii. Bunker’s team claims that the combined ultraviolet light from the galaxies located in the Ultra Deep Field is insufficient to reionize the universe. Perhaps the physics of star formation was different at these early times, or a further, yet more distant population is responsible.

The Stiavelli team shows that the same objects would be sufficient to reionize the universe, if they possessed much fewer heavier elements ? anything heavier than helium ? than those of present-day galaxies, and if the early galaxies contained more massive stars. Both these assumptions are reasonable at early epochs, since astronomers know that stars make the metals that exist in the universe. Early on, before most of the stars we see today had been formed, the amount of elements must have been much lower.

The Yan and Windhorst team started from the objects that are seen, and then carefully estimated the fraction of fainter galaxies that are not seen, even in the Hubble Ultra Deep Field. They found that the number of dwarf galaxies rapidly increases at fainter levels in the HUDF. This is like a cosmic “stock- market chart” but with very few large corporations and numerous “mom-and-pop corner stores.” Yan and Windhorst conclude that this steep increase of the faint dwarf galaxy population collectively generates enough ultraviolet light to finish reionizing the universe by redshift 6, even if the amount of heavier elements was similar to that of present-day galaxies.

The HUDF NICMOS Treasury team (Thompson/Illingworth) has taken the UDF data and other ACS survey data to get the best possible estimate of the relative numbers of bright and faint galaxies around redshift 6, only 900 million years after the big bang. The papers, led by Rychard Bouwens, show that faint galaxies dominate at this epoch, compared to more recent times, and are likely to have played a significant role in the late stages of reionization. The team has also used the HUDF NICMOS data to detect a small sample of galaxies at higher redshifts (at z=7-8), 200 million years closer in time to the big bang. The amount of reionizing light at redshifts 7-8 appears to be lower than what is seen only 200 million years later at redshift 6.

The Malhotra and Rhoads team have found a “sheet” of galaxies in the HUDF. They find that the galaxy density near redshift z=5.9 (look-back time of 12.5 billion years) is four times the galaxy density in the rest of the surveyed HUDF “core sample.” This supports theories of galaxy formation which predict that dense regions should be the first sites of galaxy formation. This evidence for an over density was bolstered by a complementary study, undertaken by Malhotra, Rhoads, and JunXian Wang, which uses the Cerro Tololo Inter-American Observatory to obtain a map of galaxies over a much wider area than the HUDF. Even with its lower sensitivity and more limited coverage in distance, this map shows that “extra” galaxies are spread like a sheet, with the HUDF located near one edge of the structure. “The presence of such structures doubtlessly affected the reionization of the universe, because the ultraviolet light that separated intergalactic hydrogen atoms into protons and electrons would have been more intense where galaxies are more common. It is then likely that reionization proceeded at different speeds in different regions of the early universe,” says Rhoads. This Hubble team used spectra to measure the distances of these galaxies very precisely.

The WFC3 built for Hubble is expected to see ten times as many distant infrared galaxies as the NICMOS. When launched, the JWST will have the light-gathering power to peruse an even earlier universe and actually see the very first stars and star clusters, which remain beyond even Hubble’s reach. These still hypothesized ultra-bright stars formed only 200 million years after the big bang (at redshift z=20, and as deduced from the WMAP image of the cosmic microwave background). They are currently believed to have heated the universe so much back then, that smaller, normal stars had to wait for the hydrogen gas to re-cool and condense before they could form.

Original Source: Hubble News Release

Posted on by Fraser Cain

Mystery at the Heart of the Milky Way

A mystery lurking at the centre of our own Milky Way galaxy – an object radiating high-energy gamma rays – has been detected by a team of UK astronomers working with international partners. Their research, published today (September 22nd) in the Journal Astronomy and Astrophysics, was carried out using the High Energy Stereoscopic System (H.E.S.S.), an array of four telescopes, in Namibia, South-West Africa.

The Galactic Centre harbours a number of potential gamma-ray sources, including a supermassive black hole, remnants of supernova explosions and possibly an accumulation of exotic ‘dark matter’ particles, each of which should emit the radiation slightly differently. The radiation observed by the H.E.S.S. team comes from a region very near Sagittarius A*, the black hole at the centre of the galaxy. According to most theories of dark matter, it is too energetic to have been created by the annihilation of dark matter particles. The observed energy spectrum best fits theories of the source being a giant supernova explosion, which should produce a constant stream of radiation.

Dr. Paula Chadwick of the University of Durham said, “We know that a giant supernova exploded in this region 10,000 years ago. Such an explosion could accelerate cosmic gamma rays to the high energies we have seen – a billion times more energy than the radiation used for X-rays in hospitals. But further observations will be needed to determine the exact source.”

Professor Ian Halliday, Chief Executive of the Particle Physics and Astronomy Research Council (PPARC) which funds UK involvement in H.E.S.S. said; “Science continues to throw out the unexpected as we push back the frontiers of knowledge.” Halliday added “The centre of our Galaxy is a mysterious place, home to exotic phenomena such as a black hole and dark matter. Finding out which of these sources produced the gamma-rays will tell us a lot about the processes taking place in the very heart of the Milky Way.”

However, the team’s theory doesn’t fit with earlier results obtained by the Japanese /Australian CANGAROO instrument or the US Whipple instrument. Both of these have detected high-energy gamma rays from the Galactic Centre in the past (observations from 1995-2002), though not with the same precision as H.E.S.S, and they were unable to pinpoint the exact location as H.E.S.S. has now done, making it harder to deduce the source. These previous results have different characteristics to the H.E.S.S. observations. It is possible that the gamma-ray source at the Galactic Centre varies over the timescale of a year, suggesting that the source is in fact a variable object, such as the central black hole.

The H.E.S.S. team hopes to unravel the mystery with further observations of the Galactic Centre over the next year or two. The full array of four telescopes will be inaugurated on September 29th 2004.

Original Source: PPARC News Release