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Physics in Universe's youth EUROPEAN SOUTHERN OBSERVATORY NEWS RELEASE Posted: May 8, 2006 Using a quasar located 12.3 billion light-years away as a beacon, a team of astronomers detected the presence of molecular hydrogen in the farthest system ever, an otherwise invisible galaxy that we observe when the Universe was less than 1.5 billion years old, that is, about 10% of its present age. The astronomers find that there is about one hydrogen molecule for 250 hydrogen atoms. A similar set of observations for two other quasars, together with the most precise laboratory measurements, allows scientists to infer that the ratio of the proton to electron masses may have changed with time. If confirmed, this would have important consequences on our understanding of physics. "Detecting molecular hydrogen and measuring its properties in the most remote parts of the Universe is important to understand the gas environment and determine the rate of star formation in the early Universe", said Cedric Ledoux, lead-author of the paper presenting the results. Although molecular hydrogen is the most abundant molecule in the Universe, it is very difficult to detect directly. For the time being, the only way to detect it directly in the far Universe is to search for its telltale signatures in the spectra of quasars or gamma- ray burst afterglows. This requires high spectral resolution and large telescopes to reach the necessary precision. A team of astronomers, comprised of Cedric Ledoux (ESO), Patrick Petitjean (IAP, Paris, France) and Raghunathan Srianand (IUCAA, Pune, India), is conducting a survey for molecular hydrogen at high redshift using the Ultraviolet and Visible Echelle Spectrograph (UVES) at ESO's Very Large Telescope. Out of the 75 systems observed up to now, 14 have firm detection of molecular hydrogen. Among these, one is found having a redshift of 4.224. While using the 12.3 billion light-years distant quasar PSS J 1443 +2724 as a beacon, the astronomers detected several features belonging to an unseen galaxy having a redshift of 4.224. In particular, many lines from molecular hydrogen were found, breaking the record for the detection of this element in the farthest object in the Universe. This also implies that the gas in this galaxy must be rather cold, about -90 to -180 degrees Celsius. In addition, several lines from 'metals' are also seen, allowing the researchers to deduce the amount of various chemical elements. "From the abundance of Nitrogen observed, we argue that it had to be produced in the late stage of the life of 4 to 8 solar mass stars," said Patrick Petitjean. "Thus, star-formation activity must have formed at least 200 to 500 million years before we are observing the galaxy, that is, when the Universe was about one billion years old". If the galaxy went through a phase of intense star-formation activity, it is now, at the time of the observations, in a rather quiescent state. "These observations demonstrate the possibility to perform these studies at the highest redshift with ESO's VLT", said Raghunathan Srianand. "In particular, the possibility to observe the interstellar medium of distant galaxies revealed by using gamma-ray bursts as beacons will boost this field in the near future." A similar set of accurate measurements of molecular hydrogen lines was made by the astronomers with UVES on the VLT towards two others quasars, Q 0405-443 and Q 0347-383. This set of data allowed the scientists to compare the ratio of the mass of a proton to that of an electron in molecular hydrogen as it is now and how it was about 12 billion years ago. To this aim, they performed extremely accurate measurements of spectral lines of hydrogen molecules in the laboratory and compared the results with the same lines observed in the spectra of these quasars. These measurements show that the mass ratio of the proton and the electron may have changed, becoming 0.002% smaller in the past twelve billion years. Albeit such a change may look tiny, it would have important consequences on our understanding of physics. The scientists stress however that their result is just an 'indication', not yet a 'proof' and that it should be confirmed by further measurements, both astronomical and in the laboratory. |
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A seven-person crew featuring payload specialists from France and Saudi Arabia flew aboard the June 1985 mission of space shuttle Discovery. They narrate the highlights of STS-51G in this post-flight film. Three communications satellites -- for Mexico, the Arab countries and the U.S. -- were launched from the payload bay. And the SPARTAN 1 astrophysics spacecraft was deployed from the shuttle's robot arm for a two-day freeflight to make its science observations before being retrieved and returned to Earth.
The flight of Spacelab 3 aboard Challenger in April/May 1985 was a week-long scientific research mission using a laboratory tucked in the shuttle's payload bay. Experiments focused on material and fluid behaviors in weightlessness, plus observations of monkeys in the lab. The crew also watched amazing auroral displays over Earth. This post-flight crew film shows the highlights of STS-51B and includes remarkable views out the shuttle cockpit window during launch showing the Chesapeake Bay, New York City and Cape Cod as Challenger soared up the eastern seaboard.
Discovery launched April 12, 1985 on the STS-51D mission. A U.S. military communications satellite, known as Leasat 3, failed to activate after its deployment from the payload bay. That set the stage for a spacewalk -- the shuttle program's first unplanned EVA -- to attach handcrafted "Flyswatter" objects on the shuttle robotic arm to hit a timing switch on the satellite. The rescue attempt did not succeed. Upon landing at Kennedy Space Center, Discovery blew a tire. The crew, including Senator Jake Garn of Utah, narrate this post-flight film of highlights from the week-long mission.
NASA managers hold this news conference April 28 to give an update on plans for the next space shuttle mission, the ongoing external fuel tank testing and debates over further modifications.
The Boeing Delta 2 rocket carrying the CALIPSO and CloudSat atmospheric research spacecraft lifts off at 3:02 a.m. local time April 28 from Vandenberg Air Force Base, California.
Inside the Vehicle Assembly Building, the external fuel tank for the STS-121 space shuttle mission is hoisted into position for attachment with the twin solid rocket boosters atop a mobile launch platform. The tank, ET-119, will carry the liquid oxygen and liquid hydrogen to feed Discovery's three main engines during launch.
In preparation for space shuttle Discovery's departure from its Orbiter Processing Facility hangar for rollover to the Vehicle Assembly Building and mating with the tank and boosters, the ship's 60-foot long payload bay doors are swung shut.