Universe Today

Image credit: NASA

Two major components of the International Space Station arrived at NASA’s Kennedy Space Center in Florida this week. Node 2, built by the European Space Agency, will increase the station’s living and work space, while the Japanese Experiment Module (JEM) will enhance its research capabilities. NASA engineers will perform integration tests over the course of the summer and then the modules will be moved to the KSC Space Station Processing Facility for a future launch on the space shuttle.

After traveling thousands of miles, two major components of the International Space Station completed the first leg of a journey that will eventually end 240 miles above the Earth. NASA’s Node 2, built for the agency by the European Space Agency (ESA) in Italy, and the Pressurized Module of the Japanese Experiment Module (JEM) arrived in Florida and are
being transported to the Kennedy Space Center (KSC) this week.

“Delivery of these components, built in Europe and Japan, to KSC for integrated testing prior to flight is yet another indication of the significant global cooperation and proactive planning required for successful operation of the International Space Station program,” said Bill Gerstenmaier, NASA’s Station Program Manager. “Their arrival in the United States signifies the Space Station international partnership is continuing to move forward with the steps necessary to construct our unique research platform in space,” he said.

The arrival of Node 2, the next pressurized module to be installed on the Station, sets in motion the final steps toward completing assembly of essential U.S. components. When
installed, Node 2 will increase the living and working space inside the Space Station to approximately 18,000 cubic feet. It will also allow the addition of international laboratories
from Europe and Japan.

The Pressurized Module is the first element of the JEM, named “Kibo” (Hope), to be delivered to KSC. The JEM is Japan’s primary contribution to the Station. It will enhance the unique research capabilities of the orbiting complex by providing an additional environment for astronauts to conduct science experiments.

The JEM also includes an exposed facility (platform) for space environment experiments, a robotic manipulator system, and two logistics modules. The various JEM components will be
assembled in space over the course of three Shuttle missions.

An Airbus Beluga heavy-lift aircraft, carrying Node 2, departed May 30 from Turin, Italy, where the Italian Space Agency’s (ASI) contractor, Alenia Spazio, built it. Following post-transportation inspections, ASI will formally transfer ownership of Node 2 to ESA, which, in turn, will sign it over to NASA.

The container transport ship carrying JEM departed May 2 from Yokohama Harbor in Japan for the voyage to the United States. The National Space Development Agency of Japan (NASDA) developed the laboratory at the Tsukuba Space Center near Tokyo.

Later this summer, integrated testing will confirm module compatibility and, ultimately, lead to pre-launch processing at KSC’s Space Station Processing Facility.

Original Source: NASA News Release

Image credit: RAVE

Researchers from 11 countries are working together to measure the motion and composition of 50 million stars in the Milky Way. This new survey is called RAVE (Radial Velocity Experiment), and astronomers will be able to use the data gathered to construct a very detailed history of our galaxy. They will be able to determine which widely separated stars were formed at a single location, and help answer competing theories about how our galaxy formed. The pilot phase of the project will begin with the UK Schmidt telescope which can measure 600 stars a night, and then production will pick up as other observatories join the hunt.

Clues to how galaxies formed in the early Universe lie right under our nose – in our own Galaxy. The Galaxy formed by the accretion of infalling satellite galaxies, many astronomers think. Theoretical models of the formation of galaxies predict such a scenario. But not all astronomers are convinced yet and the topic is still controversial.

Now researchers from eleven countries have launched an ambitious project to reconstruct our Galaxy’s history by gathering key components of motion and chemi cal compositions for its apparently brightest 50 million stars.

RAVE (RAdial Velocity Experiment) is an all-sky stellar spectroscopy survey just started on the 1.2-m UK Schmidt telescope in eastern Australia.

Projects such as Hipparcos and Tycho have accurately measured the positions and proper motions – movement across the sky – of more than 2.5 million stars.

But to get a complete picture of stellar motions, and thus to enable astronomers to reconstruct the structure and formation history of our Galaxy, they also need radial velocities – the movement of stars towards or away from the observer. And before RAVE began only about 20,000 stellar radial velocities were in the archives.

RAVE will be able to achieve velocities accurate to within 2 km/s – about 1% of the speed at which stars typically move in the Galaxy.

“With this accuracy and this number of radial velocities we will be able to identify dozens, perhaps hundreds, of streams of stars in the solar vicinity. The streams represent debris from disrupted old satellite galaxies now engulfed by our Galaxy,” said Professor Matthias Steinmetz, Director at the Astrophysical Institute Potsdam and leader of the RAVE science team.

Even after plunging into our Galaxy, the stars of a satellite galaxy continue to move as a coherent group, and can be identified by their common velocity even after billions of years. However, only a very few of those disrupted satellites have been identified to date.

RAVE will also gather the chemical compositions of stars. These should help show which widely separated stars were formed at a common site. They should also determine whether these stars have been formed before or after the satellite galaxy of which they were a part broke up.

“RAVE will help us decide between competing models for the formation of the various structures of the Galaxy, such as the central bulge of stars and the so-called ‘thick disk’,” said Steinmetz.

“For a survey such as this, field of view is more important than aperture. The UK Schmidt telescope is a perfect tool for this work,” said Professor Brian Boyle, Director of the Anglo-Australian Observatory, which operates the telescope. The field of view of the UK Schmidt telescope covers an area more than 100 times larger than that of the Moon.

RAVE’s initial pilot phase is being carried out with the 6dF (six-degree field) instrument on the UK Schmidt. Designed and built by the Anglo-Australian Observatory, the 6dF instrument is a ‘pick and place’ robot that positions 150 fibres on the telescope’s focal plane.

Using 6dF, astronomers can collect up to 600 stellar spectra per night. And by 2005 they plan to have 100,000 – five times as many as have been measured since Hermann Carl Vogel started such work at the Astrophysical Observatory Potsdam in 1888.

In 2006 the pace of data collection will pick up even further, when 6dF instrument is replaced by a radical new instrument from the AAO – UKidna, with 2250 fibres mounted on independently movable spines.

“With UKidna we’ll be taking up to 22,000 spectra on a clear night,” said Boyle.

“Then we’ll be able to push beyond our local Galactic neighbourhood, out into the furthest corners of the Milky Way,” said Professor Rosie Wyse of Johns-Hopkins University in Baltimore.

As well as uncovering the history of our Galaxy, RAVE will establish a huge database of stellar spectra – by far the largest to date.

“This will be a vast resource for studies of the properties and evolution of stars,” said Professor Ulisse Munari of the Padova Observatory in Asagio.

With its large database of stellar spectra RAVE will also provide an ideal training set for the design of future space missions such as the European Space Agency’s cornerstone mission GAIA, which will attempt to measure positions and velocities of up to a billion stars in the Milky Way.

Original Source: AIP News Release

Image credit: NRAO

Gamma ray bursts (GRB) are the largest known explosions in the Universe; immensely powerful, quick to fade, but usually incredibly far away. Astronomers with the National Radio Astronomy Observatory got lucky, though, when they analyzed a recent GRB and discovered it was only 2.6 billion light-years away (most are usually 4 times more distant). What causes these bursts is a mystery, but the theories usually incorporate black holes in some catastrophic way – colliding into another black hole; wrapping a magnetic field like a spring, etc. This close burst didn’t answer the mystery, but it did allow the astronomers to rule out one idea, that material from a GRB blasts out like “cannonballs”.

The closest Gamma Ray Burst (GRB) yet known is providing astronomers with a rare opportunity to gain information vital to understanding these powerful cosmic explosions. Extremely precise radio-telescope observations already have ruled out one proposed mechanism for the bursts.

“This is the closest and brightest GRB we’ve ever seen, and we can use it to decipher the physics of how these bursts work,” said Greg Taylor of the National Radio Astronomy Observatory (NRAO) in Socorro, NM. Taylor worked with Dale Frail, also of the NRAO, along with Prof. Shri Kulkarni and graduate student Edo Berger of Caltech in studying a GRB detected on March 29, 2003. The scientists presented their findings to the American Astronomical Society’s meeting in Nashville, TN.

VLBA IMAGE of GRB 030329

CREDIT: NRAO/AUI/NSF
(Click on Image for Larger Version)

Taylor and Frail used the National Science Foundation’s (NSF) Very Long Baseline Array (VLBA) and other radio telescopes to study the burst, known as GRB 030329. In a series of observations from April 1 to May 19, they determined the size of the expanding “fireball” from the burst and measured its position in the sky with great precision.

At a distance of about 2.6 billion light-years, GRB 030329 is hardly next door. However, compared to other GRBs at typical distances of 8-10 billion light-years, it presents an easier target for study.

“We only expect to see one burst per decade this close,” said Frail.

The precise measurement of the object’s position allowed the scientists to show that one theoretical model for GRBs can be ruled out. This model, proposed in 2000, says that the radio-wave energy emitted by the GRB comes from “cannonballs” of material shot from the explosion at extremely high speeds.

“The ‘cannonball model’ predicted that we should see the radio-emitting object move across the sky by a specific amount. We have not seen that motion,” Taylor said.

The currently standard “fireball model” of GRBs says that the radio emission comes from a rapidly-expanding shock wave. This model was first proposed by Peter Meszaros, Bohdan Paczynski and Sir Martin Rees, who won the American Astronomical Society’s Bruno Rossi Prize in 2000 for their work. In this standard model, as the shock wave expands outward, the emission becomes fainter, but the center of the observed emission does not change position.

The cannonball model, however, proposes that the emission arises from distinct concentrations of matter shot outward from the burst. As they move farther from the burst, their motion should be detected as a change in their position in the sky. On April 3, proponents of the cannonball model predicted a specific amount of motion for GRB 030329 and suggested that the VLBA’s sharp radio “vision” could detect the motion and confirm their prediction.

Instead, “our observations are consistent with no motion at all,” Taylor said. “This is at odds with the cannonball model — they made a specific prediction based on their model and the observations do not bear them out,” he added.

The scientists’ direct measurement of the size of the GRB fireball also will provide new insights into the physics behind the burst.

“By directly measuring the size and the expansion rate, we can start putting some real limits on the physics involved,” Taylor said. First, he said, “We already can confirm that the fireball is expanding at nearly the speed of light, as the standard model predicts. Next, once our May observations are fully analyzed, we can put limits on the energy of the burst and provide a test of the standard model.”

Taylor and Frail observed GRB 030329 with the VLBA on April 1 and April 6. On April 22, they used the 100-meter radio telescope in Effelsberg, Germany in addition to the VLBA. On May 19, they used the VLBA, the Very Large Array (VLA) in New Mexico, the NSF’s Robert C. Byrd Green Bank Telescope in West Virginia, and the Effelsberg telescope.

In addition to gamma-ray and X-ray observations, visible light from GRB 030329 was observed by 65 telescopes around the world. At its brightest, the visible light from this burst was detectable with moderate-sized amateur telescopes.

Gamma Ray Bursts were first detected in 1967 by a satellite monitoring compliance with the 1963 atmospheric nuclear test-ban treaty. For three decades thereafter, astronomers were unable to determine their distances from Earth, and thus were unable to begin understanding the physics underlying the explosions. In 1997, the first distance measurements were made to GRBs, and the NSF’s Very Large Array (VLA) detected the first radio emission from a GRB afterglow.

Once scientists determined that GRBs originate in distant galaxies and that they probably occur in regions of those galaxies where stars are actively forming, some 200 proposed models for what causes GRBs were reduced to a handful of viable models.

Most scientists now believe that GRBs arise from a violent explosion that ends the life of a star much more massive than the Sun. Whereas such an explosion as a typical supernova leaves a dense neutron star, a GRB explosion leaves a black hole, a concentration of mass with gravitational pull so strong that not even light can escape it.

The VLBA is a continent-wide system of ten radio- telescope antennas, ranging from Hawaii in the west to the U.S. Virgin Islands in the east, providing the greatest resolving power, or ability to see fine detail, in astronomy. Dedicated in 1993, the VLBA is operated from the NRAO’s Array Operations Center in Socorro, New Mexico.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Original Source: NRAO News Release