Posted on by Fraser Cain

Galaxies and Their Black Holes Grow Together

Image credit: SDSS

After surveying 120,000 nearby galaxies as part of the Sloan Digital Survey, a team of astronomers have found evidence that the growth of supermassive black holes at the heart of most galaxies is closely matched to the rate of new star formation. The growth rate of the black holes was determined by measuring the amount of material being consumed at the heart of the galaxy. The actual nature of this relationship is still unknown, but future surveys will help to uncover more details.

By studying more than 120,000 nearby galaxies observed as part of the Sloan Digital Sky Survey, a team of astronomers from Germany and the United States has been able to show that the growth of supermassive black holes is closely linked with the birth of new stars in their host galaxies.

This discovery — a first direct glimpse of the connection between galaxy formation and black hole formation — was announced July 14 at the International Astronomical Union’s Maps of the Cosmos Symposium in Sydney, Australia. The paper, The Host Galaxies of the Active galactic nuclei, was submitted to the Monthly Notices of the Royal Astronomical Society.

One of the most remarkable discoveries of recent years has been the demonstration that every large galaxy harbors, at its core, a black hole weighing many million times as much as the Sun, explained research team leader Dr. Guinevere Kauffmann of the Max Planck Institute for Astrophysics in Garching, Germany.

Furthermore, Kauffmann said the mass of this central black hole is very closely related to the properties of the galaxy in which it is embedded. This implies that the formation of the black hole is intimately entwined with that of its galaxy, but the nature of this link remains obscure.

Does the black hole control the growth of its host, or does the galaxy limit the growth of its central black hole? Do black holes and galaxy growth form some kind of a symbiotic relationship? These questions can only be answered by careful study of the growth process, she said.

Co-team leader Dr. Timothy Heckman of the Johns Hopkins University, Baltimore, Md., explained that as black holes grow they release prodigious amounts of energy, in extreme cases outshining their host galaxy, to produce a bright quasar. The main epoch of quasar activity, and perhaps of black hole growth, occurred when the Universe was between a third and a tenth of its present age of 14 billion years.

Heckman said large galaxies are thought to have formed through the collapse and merging of smaller systems during this same time period. Black hole growth is still detectable in galaxy nuclei today, however, and stars still form in these inner regions. “Since nearby galaxies can be studied much more easily than their distant and more spectacular ancestors, it is no surprise that the link between black hole growth and galaxy growth first became apparent in our own backyard,” he said. The light from these nearby galaxies studied took less than one billion years to reach us (compared to almost ten billion years for most quasars). These are close enough for researchers us to study in some detail but long after the rapid building process for both black holes and galaxies has subsided to a lower level.

By searching for tell tale features in the spectra of more than 120,000 galaxies, the SDSS team was able to show that more than 20,000 of them contain black holes that are currently growing. The growth rate of the black hole is inferred from the strength of characteristic emission lines known to be correlated with how much material is falling onto the black hole.

These growing black holes are located almost exclusively in galaxies more massive than the Milky Way. Massive galaxies where black hole growth is currently weak or absent typically have the structure and star content of old elliptical galaxies, which finished making stars long ago, researchers explained. Galaxies where black hole growth is currently strong have similar mass and structure, but show evidence for substantial recent star formation.

In its conclusion, the team said that as the rate of black hole growth increases, so does the amount of star formation within the past 100 million years, recent in astronomical terms. In the most extreme objects the black hole is growing as fast as in bright quasars and the galaxy is dominated by young stars.

They say that this probably means that the black hole is growing by swallowing some of the same supply of relatively cold and dense gas from which stars are forming elsewhere in the galaxy. The stellar mass of these galaxies and the masses of their central black holes are clearly growing together. Like chicken and egg, neither black hole nor galaxy can be said to come first; each is necessary for the other.

Original Source: SDSS News Release

Posted on by Fraser Cain

Neutrino-Seeking Telescope Lodged in Ice

Image credit: UW-Madison

A new telescope lodged in the ice of Antarctica has completed the first map of the high-energy neutrino sky. AMANDA II consists of 677 glass detectors in the shape of a cylinder sunk into the Antarctic ice at a depth greater than 500 metres. It actually looks down, through the entire Earth to view the Northern sky for neutrinos, which move at high velocity and pass through almost all matter unhindered. AMANDA II has discovered neutrinos with 100 times the energy of any produced in laboratory experiments on Earth.

A novel telescope that uses the Antarctic ice sheet as its window to the cosmos has produced the first map of the high-energy neutrino sky.

The map, unveiled for astronomers here today (July 15) at a meeting of the International Astronomical Union, provides astronomers with their first tantalizing glimpse of very high-energy neutrinos, ghostly particles that are believed to emanate from some of the most violent events in the universe – crashing black holes, gamma ray bursts, and the violent cores of distant galaxies.

“This is the first data with a neutrino telescope with realistic discovery potential,” says Francis Halzen, a University of Wisconsin-Madison professor of physics, of the map compiled using AMANDA II, a one-of-a-kind telescope built with support from the National Science Foundation (NSF) and composed of arrays of light-gathering detectors buried in ice 1.5 kilometers beneath the South Pole. “To date, this is the most sensitive way ever to look at the high-energy neutrino sky,” he says.

The ability to detect high-energy neutrinos and trace them back to their points of origin remains one of the most important quests of modern astrophysics.

Because cosmic neutrinos are invisible, uncharged and have almost no mass, they are next to impossible to detect. Unlike photons, the particles that make up visible light, and other kinds of radiation, neutrinos can pass unimpeded through planets, stars, the vast magnetic fields of interstellar space and even entire galaxies. That quality – which makes them very hard to detect – is also their greatest asset because the information they harbor about cosmologically distant and otherwise unobservable events remains intact.

The map produced by AMANDA II is preliminary, Halzen emphasizes, and represents only one year of data gathered by the icebound telescope. Using two more years of data already harvested with AMANDA II, Halzen and his colleagues will next define the structure of the sky map and sort out potential signals from statistical fluctuations in the present map to confirm or disprove them.

The significance of the map, according to Halzen, is that it proves the detector works. “It establishes the performance of the technology,” he says, “and it shows that we have reached the same sensitivity as telescopes used to detect gamma rays in the same high-energy region” of the electromagnetic spectrum. Roughly equal signals are expected from objects that accelerate cosmic rays, whose origins remain unknown nearly a century after their discovery.

Sunk deep into the Antarctic ice, the AMANDA II (Antarctic Muon and Neutrino Detector Array) Telescope is designed to look not up, but down, through the Earth to the sky in the Northern Hemisphere. The telescope consists of 677 glass optical modules, each the size of a bowling ball, arrayed on 19 cables set deep in the ice with the help of high-pressure hot-water drills. The array transforms a cylinder of ice 500 meters in height and 120 meters in diameter into a particle detector.

The glass modules work like light bulbs in reverse. They detect and capture faint and fleeting streaks of light created when, on occasion, neutrinos crash into ice atoms inside or near the detector. The subatomic wrecks create muons, another species of subatomic particle that, conveniently, leaves an ephemeral wake of blue light in the deep Antarctic ice. The streak of light matches the path of the neutrino and points back to its point of origin.

Because it provides the first glimpse of the high-energy neutrino sky, the map will be of intense interest to astronomers because, says Halzen, “we still have no clue how cosmic rays are accelerated or where they come from.”

The fact that AMANDA II has now identified neutrinos up to one hundred times the energy of the particles produced by the most powerful earthbound accelerators raises the prospect that some of them may be kick-started on their long journeys by some of the most supremely energetic events in the cosmos. The ability to routinely detect high-energy neutrinos will provide astronomers not only with a lens to study such bizarre phenomena as colliding black holes, but with a means to gain direct access to unedited information from events that occurred hundreds of millions or billions of light years away and eons ago.

“This map could hold the first evidence of a cosmic accelerator,” Halzen says. “But we are not there yet.”

The hunt for sources of cosmic neutrinos will get a boost as the AMANDA II Telescope grows in size as new strings of detectors are added. Plans call for the telescope to grow to a cubic kilometer of instrumented ice. The new telescope, to be known as IceCube, will make scouring the skies for cosmic neutrino sources highly efficient.

“We will be sensitive to the most pessimistic theoretical predictions,” Halzen says. “Remember, we are looking for sources, and even if we discover something now, our sensitivity is such that we would see, at best, on the order of 10 neutrinos a year. That’s not good enough.”

Original Source: WISC News Release

Posted on by Fraser Cain

Measuring the Earth’s Ozone Levels with Four Satellites

Image credit: NASA

A series of NASA satellites are measuring ozone levels in the Earth’s atmosphere with such precision that they can tell where’s it’s naturally occurring and where it’s caused by pollution. The satellites included NASA’s Terra, Tropical Rainfall Measuring Mission, Earth Probe/TOMS, and the ESA’s ERS-2 satellite, and they were able to record fires and lightning flashes around the world. Scientists were surprised to find that larger quantities of ozone over the tropical Atlantic were actually formed by lightning strikes and not pollution as originally though.

During summertime ozone near the Earth’s surface forms in most major U.S. cities when sunlight and heat mix with car exhaust and other pollution, causing health officials to issue “ozone alerts.” But in other parts of the world, such as the tropical Atlantic, this low level ozone appears to originate naturally in ways that have left scientists puzzled. Now, NASA-funded scientists using four satellites can tell where low level ozone pollution comes from and whether it was manmade or natural.

Atmospheric scientist David Edwards and his colleagues from the National Center for Atmospheric Research (NCAR) and collaborators in Canada and Europe have studied this problem using satellite data from three NASA spacecraft, one from the European Space Agency (ESA), and a computer model from NCAR. They were surprised to find that a greater amount of near-surface ozone over the tropical Atlantic develops as a result of lightning instead of agricultural and fossil fuel burning.

Their findings appeared in a recent issue of the American Geophysical Union’s Journal of Geophysical Research Atmospheres. The formation of ozone involves several factors, such as lightning and pollution from agricultural and fossil fuel burning, which is why it was helpful to use NASA’s multiple satellites to look at each in turn.

NASA satellites included Terra, the Tropical Rainfall Measuring Mission (TRMM), and Earth Probe/TOMS. ESA’s ERS-2 satellite was also used to look at ozone, and NCAR’s MOZART-2 (Model for OZone And Related chemical Tracers) computer model was used to simulate the chemical composition of the atmosphere.

Because the different satellite instruments could detect fires, lightning flashes, and the resulting pollution and ozone in the atmosphere, respectively, they provided a bird’s-eye global view of what was going on, and the computer model helped tie all the pieces together.

Fires create smoke and carbon monoxide, and lightning creates nitrogen oxides (NOx). All of these come together with other unstable compounds in a chemical soup, and sunlight helps trigger the reaction that helps form ozone. The scientists found that in the early part of the year, the intense fires set by farmers for land-clearing and traditional cultivation in north-western Africa, just south of the Sahara Desert, resulted in large amounts of pollution that they could track using satellite images as it spread over the Atlantic towards South America. This pollution greatly increased ozone at low altitudes near the fires.

However, when Edwards and his colleagues looked at areas of elevated ozone levels measured by satellites and aircraft over the Atlantic south of the equator, they were more surprised to find that this ozone was caused mainly by lightning rather than the fires.

In other parts of the world, especially near cities, ozone near Earth’s surface is often made from pollution as a result of industrial fossil-fuel burning and cars. Understanding where the pollution comes from in each case is important for improving our air quality.

NASA’s Measurements of Pollution in the Troposphere (MOPITT) instrument aboard the Terra satellite is a joint NASA/Canadian Space Agency mission that measured carbon monoxide concentrations at various levels of the atmosphere. The TOMS instrument on EP/TOMS measured tropical tropospheric ozone over the mid-Atlantic. The TRMM satellite counted the number of fires in a region using its Visible/Infrared Scanner (VIRS), and also catalogued lightning flash data from its Lightning Imaging Sensor (LIS). The satellite data was then interpreted using the MOZART-2 computer model.

Previously, scientists used TOMS observations to get a general idea of where the tropospheric ozone levels were high, but it was often difficult to say where the ozone came from and which pollution source or natural process led to its creation. Only recently has the 4 satellite combination enabled scientists to make this distinction.

This research was funded by NASA’s Earth Science Enterprise (ESE), in cooperation with the National Science Foundation, sponsor of NCAR. NASA’s ESE is dedicated to understanding the Earth as an integrated system and applying Earth System Science to improve prediction of climate, weather and natural hazards using the unique vantage point of space.

Original Source: NASA News Release

Posted on by Fraser Cain

Destroyed Australian Observatory to Be Rebuilt

Image credit: ANU

In early 2003 bushfires destroyed much of Australia’s Stromlo Observatory, including five telescopes and several support buildings. On Sunday, July 13, the Australian National University unveiled plans to rebuild the facilities on Mt Stromlo. In addition to building two new telescopes (including a two-metre robotic telescope), the University will also reconstruct several heritage buildings destroyed in the fire.

Bushfires in January destroyed more than $40 million worth of facilities and equipment at the Observatory, including five telescopes, workshops, an important heritage building and seven houses.

Mt Stromlo will resume its mantle as the home of Australian astronomy through the planned redevelopment, which includes the placement of two telescopes on Mount Stromlo and one at the ANU Siding Spring Observatory near Coonabarabran, reconstruction of heritage buildings and enhanced viewing facilities for the public, including a newvirtual reality theatre.

The redevelopment will ensure Mt Stromlo remains a world-class astronomy research and education facility, ANU Vice-Chancellor Professor Ian Chubb said. Funding for the redevelopment, including insurance claims, is yet to be finalised, so the plan allows for staged construction.

?Mt Stromlo is not just an icon of Australian science, it is the workplace of number of the world?s leading researchers,? Professor Chubb said.

?The January fires devastated the observatory, but it is time to look ahead to the new Stromlo.

?It is clear that a site with such heritage, renowned as a powerhouse of research and innovation around the world, must be re-equipped with world-class facilities. The University, the International scientific community and the Australian public would not and could not accept a second-class Stromlo.?

The planned redevelopment includes:
? The Advanced Instruments and Engineering Facility, which will replace the workshops destroyed in the blaze, offering expanded design and manufacture capabilities for precision optical instruments and a research and development program focusing on Extremely Large Telescopes

? A new robotically-controlled two-metre telescope, the Phoenix

? The world?s fastest sky-mapping telescope, the Skymapper, to be built at the ANU Siding Spring Observatory, but controlled from Mt Stromlo through a broadband link

? Restoration of the historic 1924 Admin building, to house a rebuilt library and offices

? Restoration of the historic 23cm Oddie Telescope

? Housing for Staff and Students

? A new virtual reality theatre, allowing visitors to fly through our universe in 3D

The Director of the Research School of Astronomy and Astrophysics, Professor Penny Sackett, said Mt Stromlo had opened the eyes of tens of thousands of Australians to science and served as a vital resource to international astronomy for decades ? and would continue to play this role in future.

?The fires destroyed much of our infrastructure, but left our most important asset intact ? our people,? Professor Sackett said.

?The day after fires, we committed to restoring Stromlo and its network of facilities as a pillar of Australian science.

?Three weeks after the fires, our staff were back at work on the mountain, working in two office buildings which were largely undamaged.

?We can not and we should not reconstruct a carbon copy of the old Stromlo. This new design is overwhelmingly oriented around meeting the needs of staff, students and visitors ? while also ensuring Stromlo retains its status as an internationally important observatory.

?For decades, Stromlo and Siding Spring have been operated as integrated observatories, combining the virtues of a control base close to ANU, close to the nation?s capital and accessible to the community with a primary observation base offering optimal astronomical and climatic conditions.

?The new design retains telescopes and the research hub at Stromlo, but provides even stronger integration with the University?s Siding Spring resources, ultimately providing a more powerful research facility for Australia.?

Original Source: ANU News Release

Posted on by Fraser Cain

New Galaxy Clusters Discovered

Image credit: ESO

A team of European and Chilean astronomers have discovered several large clusters of galaxies at a distance of 8 billion light years which should provide insights into the structure and evolution of the Universe. The galaxy clusters were discovered by combining images from the ESA’s XMM-Newton space telescope and the ESO’s Very Large Telescope. Galaxy clusters aren’t spread evenly, but appear strung through the Universe like a web, and so far it seems like the shape of these clusters hasn’t changed since the Universe was very young..

Using the ESA XMM-Newton satellite, a team of European and Chilean astronomers [2] has obtained the world’s deepest “wide-field” X-ray image of the cosmos to date. This penetrating view, when complemented with observations by some of the largest and most efficient ground-based optical telescopes, including the ESO Very Large Telescope (VLT), has resulted in the discovery of several large clusters of galaxies.

These early results from an ambitious research programme are extremely promising and pave the way for a very comprehensive and thorough census of clusters of galaxies at various epochs. Relying on the foremost astronomical technology and with an unequalled observational efficiency, this project is set to provide new insights into the structure and evolution of the distant Universe.

The universal web
Unlike grains of sand on a beach, matter is not uniformly spread throughout the Universe. Instead, it is concentrated into galaxies which themselves congregate into clusters (and even clusters of clusters). These clusters are “strung” throughout the Universe in a web-like structure, cf. ESO PR 11/01.

Our Galaxy, the Milky Way, for example, belongs to the so-called Local Group which also comprises “Messier 31”, the Andromeda Galaxy. The Local Group contains about 30 galaxies and measures a few million light-years across. Other clusters are much larger. The Coma cluster contains thousands of galaxies and measures more than 20 million light-years. Another well known example is the Virgo cluster, covering no less than 10 degrees on the sky !

Clusters of galaxies are the most massive bound structures in the Universe. They have masses of the order of one thousand million million times the mass of our Sun. Their three-dimensional space distribution and number density change with cosmic time and provide information about the main cosmological parameters in a unique way.

About one fifth of the optically invisible mass of a cluster is in the form of a diffuse hot gas in between the galaxies. This gas has a temperature of the order of several tens of million degrees and a density of the order of one atom per liter. At such high temperatures, it produces powerful X-ray emission.

Observing this intergalactic gas and not just the individual galaxies is like seeing the buildings of a city in daytime, not just the lighted windows at night. This is why clusters of galaxies are best discovered using X-ray satellites.

Using previous X-ray satellites, astronomers have performed limited studies of the large-scale structure of the nearby Universe. However, they so far lacked the instruments to extend the search to large volumes of the distant Universe.

The XMM-Newton wide-field observations
Marguerite Pierre (CEA Saclay, France), with a European/Chilean team of astronomers known as the XMM-LSS consortium [2], used the large field-of-view and the high sensitivity of ESA’s X-ray observatory XMM-Newton to search for remote clusters of galaxies and map out their distribution in space. They could see back about 7,000 million years to a cosmological era when the Universe was about half its present size and age, when clusters of galaxies were more tightly packed.

Tracking down the clusters is a painstaking, multi-step process, requiring both space and ground-based telescopes. Indeed, from X-ray images with XMM, it was possible to select several tens of cluster candidate objects, identified as areas of enhanced X-radiation (cf PR Photo 19b/03).

But having candidates is not enough ! They must be confirmed and further studied with ground-based telescopes. In tandem with XMM-Newton, Pierre uses the very-wide-field imager attached to the 4-m Canada-France-Hawaii Telescope, on Mauna Kea, Hawaii, to take an optical snapshot of the same region of space. A tailor-made computer programme then combs the XMM-Newton data looking for concentrations of X-rays that suggest large, extended structures. These are the clusters and represent only about 10% of the detected X-ray sources. The others are mostly distant active galaxies.

Back to the Ground
When the programme finds a cluster, it zooms in on that region and converts the XMM-Newton data into a contour map of X-ray intensity, which is then superimposed upon the CFHT optical image (PR Photo 19c/03). The astronomers use this to check if anything is visible within the area of extented X-ray emission.

If something is seen, the work then shifts to one of the world’s prime optical/infrared telescopes, the European Southern Observatory’s Very Large Telescope (VLT) at Paranal (Chile). By means of the FORS multi-mode instruments, the astronomers zoom-in on the individual galaxies in the field, taking spectral measurements that reveal their overall characteristics, in particular their redshift and hence, distance.

Cluster galaxies have similar distances and these measurement ultimately provide, by averaging, the cluster’s distance as well as the velocity dispersion in the cluster. The FORS instruments are among the most efficient and versatile for this type of work, taking on the average spectra of 30 galaxies at a time.

The first spectroscopic observations dedicated to the identification and redshift measurement of the XMM-LSS galaxy clusters took place during three nights in the fall of 2002.

As of March 2003, there were only 5 known clusters in the literature at such a large redshift with enough spectroscopically measured redshifts to allow an estimate of the velocity dispersion. But the VLT allowed obtaining the dispersion in a distant cluster in 2 hours only, raising great expectations for future work.

700 spectra…
Marguerite Pierre is extremely content : Weather and working conditions at the VLT were optimal. In three nights only, 12 cluster fields were observed, yielding no less than 700 spectra of galaxies. The overall strategy proved very successful. The high observing efficiency of the VLT and FORS support our plan to perform follow-up studies of large numbers of distant clusters with relatively little observing time. This represents a most substantial increase in efficiency compared to former searches.

The present research programme has begun well, clearly demonstrating the feasibility of this new multi-telescope approach and its very high efficiency. And Marguerite Pierre and her colleagues are already seeing the first tantalising results: it seems to confirm that the number of clusters 7,000 million years ago is little different from that of today. This particular behaviour is predicted by models of the Universe that expand forever, driving the galaxy clusters further and further apart.

Equally important, this multi-wavelength, multi-telescope approach developed by the XMM-LSS consortium to locate clusters of galaxies also constitutes a decisive next step in the fertile synergy between space and ground-based observatories and is therefore a basic building block of the forthcoming Virtual Observatory.

More information
This work is based on two papers to be published in the professional astronomy journal, Astronomy and Astrophysics (The XMM-LSS survey : I. Scientific motivations, design and first results by Marguerite Pierre et al., astro-ph/0305191 and The XMM-LSS survey : II. First high redshift galaxy clusters: relaxed and collapsing systems by Ivan Valtchanov et al., astro-ph/0305192).

Dr. M. Pierre will give an invited talk on this subject at the IAU Symposium 216 – Maps of the Cosmos – this Thursday July 17, 2003 during the IAU General Assembly 2003 in Sydney, Australia.

Notes
[1]: This a coordinated ESO/ESA release.

[2]: The XMM-LSS consortium is led by the Service d’Astrophysique du CEA (France) and consists of institutes from the UK, Ireland, Denmark, The Netherlands, Belgium, France, Italy, Germany, Spain and Chile. The homepage of the XMM-LSS project can be found at http://vela.astro.ulg.ac.be/themes/spatial/xmm/LSS/index_e.html

[3]: In astronomy, the “redshift” denotes the fraction by which the lines in the spectrum of an object are shifted towards longer wavelengths. Since the redshift of a cosmological object increases with distance, the observed redshift of a remote galaxy also provides an estimate of its distance.

Original Source: ESO News Release

Posted on by Fraser Cain

Universe Today Forums

After running the “Discuss this story” links for just a couple of days, it was pretty clear that giving people the opportunity to talk to each other was just what Universe Today was missing. So, I decided to expand the offering to a full-fledged discussion forum. My hope is that it can be a place where space enthusiasts can come together and hash out their ideas. Ask questions and answer them, and generally be surrounded by other people who share our passion.

Joining the forums is free, and easy to do. Just click this link, or visit the “Forum” tab whenever you visit the Universe Today. Create an account and then post away. Keep in mind that this is one of those “get out what you put in” situations. If you’re hungry for intelligent conversation about space and astronomy, then please take some time to connect with other people – we’ll all be the richer.

I’ve been working hard to get various “special guests” to provide official responses to your questions. For example, Jennifer Spencer, the Web Curator for the Gravity Probe B project provided a great answer to a reader’s question about the speed of gravity. I’ll try to get answers from the source whenever I can.

Thanks!

Fraser Cain
Publisher
Universe Today

Posted on by Fraser Cain

Gravity Probe B Arrives at Vandenberg

Image credit: NASA

NASA’s Gravity Probe B arrived at Vandenberg Air Force Base on Friday, July 11 to begin launch preparations. Once launched, the spacecraft will use four ultra-precise gyroscopes to test two predictions of Einstein’s General Theory of Relativity: how space and time are warped by the Earth, and how the Earth’s rotation drags space-time around with it. If all goes well, the spacecraft will launch on board a Boeing Delta II rocket in late 2003.

The NASA spacecraft designed to test two predictions of Einstein’s Theory of General Relativity has been shipped from the Lockheed Martin Space Systems Facility in Sunnyvale, Calif., to the launch site at Vandenberg Air Force Base, Calif., after completing environmental testing. The Marshall Center manages the Gravity Probe B program for NASA.

The NASA spacecraft designed to test two important predictions of Albert Einstein’s Theory of General Relativity was shipped yesterday from the Lockheed Martin Space Systems Facility in Sunnyvale, Calif., to the launch site at Vandenberg Air Force Base, Calif., after completing environmental testing.

NASA’s Gravity Probe B mission, also known as GP-B, will use four ultra-precise gyroscopes to test Einstein’s theory that space and time are distorted by the presence of massive objects. To accomplish this, the mission will measure two factors — how space and time are warped by the presence of the Earth, and how the Earth’s rotation drags space-time around with it.

Stanford University in Stanford, Calif., and Lockheed Martin performed the testing. Shipped by road transport, the vehicle arrived July 10 at Vandenberg for pre-launch operations in anticipation of a launch in late 2003.

NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the GP-B program. NASA’s prime contractor for the mission, Stanford University, conceived the experiment and is responsible for the design and integration of the science instrument, as well as for mission operations and data analysis. Lockheed Martin, a major subcontractor, designed, integrated and tested the spacecraft and some of its major payload components.

The erection of the Boeing Delta II launch vehicle on Space Launch Complex 2 (SLC-2) at Vandenberg Air Force Base is currently scheduled to begin on September 15 with erection of the first stage. Attachment of the nine strap-on solid rocket boosters is scheduled to occur in sets of three on September 16 – 18. The second stage is planned for mating atop the first stage on September 19. Gravity Probe B will be transported from the spacecraft hangar to SLC-2 on October 29 and hoisted atop the second stage. The Delta II fairing will be installed around the spacecraft on November 5, part of final pre-launch preparations. The launch is the responsibility of NASA’s John F. Kennedy Space Center in Florida.

Original Source: NASA News Release

Posted on by Fraser Cain

Dust Storm on Mars Visible By Amateurs

Image credit: Hubble

Now that Mars is closer than ever, amateur astronomers with regular backyard telescopes can see incredible details on the planet’s surface. On July 1, astronomers were able to see a dust storm in the Hellas Basin; four days later it was 1,800 kilometres wide, obscuring nearly a quarter of the planet. Two years ago a similar storm grew in the same region and ended up obscuring the entire planet for months. Earth and Mars will reach their closest point in 60,000 years on August 27, 2003, and the Red Planet should offer up some tremendous views.

Something is happening on Mars and it’s so big you can see it through an ordinary backyard telescope.

On July 1st a bright dust cloud spilled out of Hellas Basin, a giant impact crater on Mars’ southern hemisphere. The cloud quickly spread and by the Fourth of July was 1100 miles wide–about one-fourth the diameter of Mars itself.

“The cloud can be seen now through a telescope as small as 6 inches,” says Donald Parker, executive director of the Association of Lunar and Planetary Observers (ALPO). “Its core is quite bright.”

Parker has been tracking the cloud through his own 16-inch telescope. “A red filter helps,” he notes. “Even a piece of red or orange gelatin held between the eye and ocular will improve the visibility of the dust.”

Two years ago, a similar cloud from Hellas Basin grew until it circled the entire planet. Features on Mars long familiar to amateur astronomers–the dark volcanic terrain of Syrtis Major, for example–were hidden for months. “The planet looked like an orange billiard ball,” recalls Parker.

Will it happen again?

“No one knows,” says astronomer James Bell of Cornell University who studied the dust storm of 2001 using the Hubble telescope. “We don’t yet understand the mechanism that causes regional clouds to self-assemble into giant dust storms.”

Mars Global Surveyor and Mars Odyssey, two NASA spacecraft circling Mars, have seen many “regional storms” like the cloud near Hellas Basin now. They persist for a few days or weeks, then dissipate. Rarely do they become a planet-wide event.

“Only 10 global or planet-encircling dust storms have been reported since 1877,” notes Parker.

All dust storms on Mars, no matter what size, are powered by sunshine. Solar heating warms the martian atmosphere and causes the air to move, lifting dust off the ground.

Because the martian atmosphere is thin–about 1% as dense as Earth’s at sea level–only the smallest dust grains hang in the air. “Airborne dust on Mars is about as fine as cigarette smoke,” says Bell. These fine grains reflect 20% to 25% of the sunlight that hits them; that’s why the clouds look bright. (For comparison, the reflectivity of typical martian terrain is 10% to 15%.)

Sunlight on Mars is about to become unusually intense. The planet goes around the sun in a 9%-elliptical orbit with one end 40 million km closer to the sun than the other. Mars reaches perihelion–its closest approach to the sun–on August 30th. During the weeks around perihelion, sunlight striking Mars will be 20% more intense than the annual average.

“This means the season for dust storms is just beginning,” says Bell.

A total of four spacecraft from NASA, the European Space Agency and Japan are en route to Mars now. They include three landers and two orbiters. Will dust storms cause problems for those missions?

Probably not. NASA spacecraft have encountered Mars dust before. The Viking landers of 1976, for instance, weathered two big dust storms without being damaged. As far as researchers were concerned, it was a good opportunity to study such storms from the inside–something Mars colonists may do again one day for themselves. Viking data will give them a head start.

Five years earlier, in 1971, the Mariner 9 spacecraft reached Mars during the biggest dust storm ever recorded. The planet was completely obscured; not even the polar caps were visible. Mission controllers simply waited a few weeks for the storm to subside. Then they carried on with Mariner 9’s mission: to photograph the entire surface of the planet. It was a complete success.

As 2003 unfolds, Earth and Mars are drawing together for their closest approach in some 60,000 years on August 27th. Already in July Mars is a pleasing sight. Step outside before dawn anytime this month. Mars will be there in the southern sky, a remarkably bright red star. (If you live in the southern hemisphere, look northeast instead.)

Right: John Nemy and Carol Legate took this recent picture of bright Mars and a meteor above their campsite on Blackcomb Mountain, Whistler, British Columbia.

Even a small telescope will reveal the planet’s orange disk and its icy south polar cap. And if “seeing is good” you might catch a glimpse of some dust clouds. Swirling, surging, merging with others … building the next global dust storm? “They’re fun to watch,” says Parker. Now is a great time to see for yourself.

Original Source: NASA Science Story

Posted on by Fraser Cain

Age Wasn’t a Cause of the Columbia Disaster

During a press briefing on Friday, investigators ruled out the age of the space shuttle Columbia as a contributing cause to its destruction. With the most recent foam test, which knocked a large hole in sample shuttle wing panel, the force of the impact would have broken through, even if the panel was brand new. Investigators believe the hole in Columbia was smaller than the one in the test panel; otherwise it would have broken up much earlier upon re-entry.

Posted on by Fraser Cain

World’s Astronomers Meet in Sydney

Astronomers from around the world have descended on Sydney, Australia for the 25th general assembly of the International Astronomical Union. Around 2,000 astronomers will be in the city to attend the event which will cover a vast range of topics, such as “Young Neutron Stars and their Environments”.

During this event, astronomers are announcing all kinds of discoveries, so don’t be surprised if Universe Today is a little bigger than normal and astronomy-focused for the next few weeks. I’ll try to stay on top of it as much as possible.

If you’re in Sydney, let me know how it all goes.

Fraser Cain
Publisher
Universe Today