Astronomers Uncover a Surprising Trend In Galaxy Evolution
WASHINGTON -- A comprehensive study of hundreds of galaxies observed by the Keck telescopes in Hawaii and NASA's Hubble Space Telescope has revealed an unexpected pattern of change that extends back 8 billion years, or more than half the age of the universe.
"Astronomers thought disk galaxies in the nearby universe had settled into their present form by about 8 billion years ago, with little additional development since," said Susan Kassin, an astronomer at NASA's Goddard Space Flight Center in Greenbelt, Md., and the study's lead researcher. "The trend we've observed instead shows the opposite, that galaxies were steadily changing over this time period."
Today, star-forming galaxies take the form of orderly disk-shaped systems, such as the Andromeda Galaxy or the Milky Way, where rotation dominates over other internal motions. The most distant blue galaxies in the study tend to be very different, exhibiting disorganized motions in multiple directions. There is a steady shift toward greater organization to the present time as the disorganized motions dissipate and rotation speeds increase. These galaxies are gradually settling into well-behaved disks.
Blue galaxies -- their color indicates stars are forming within them -- show less disorganized motions and ever-faster rotation speeds the closer they are observed to the present. This trend holds true for galaxies of all masses, but the most massive systems always show the highest level of organization.
Researchers say the distant blue galaxies they studied are gradually transforming into rotating disk galaxies like our own Milky Way. "Previous studies removed galaxies that did not look like the well-ordered rotating disks now common in the universe today," said co-author Benjamin Weiner, an astronomer at the University of Arizona in Tucson. "By neglecting them, these studies examined only those rare galaxies in the distant universe that are well-behaved and concluded that galaxies didn't change."
Rather than limit their sample to certain galaxy types, the researchers instead looked at all galaxies with emission lines bright enough to be used for determining internal motions. Emission lines are the discrete wavelengths of radiation characteristically emitted by the gas within a galaxy. They are revealed when a galaxy's light is separated into its component colors. These emission lines also carry information about the galaxy's internal motions and distance.
The team studied a sample of 544 blue galaxies from the Deep Extragalactic Evolutionary Probe 2 (DEEP2) Redshift Survey, a project that employs Hubble and the twin 10-meter telescopes at the W. M. Keck Observatory in Hawaii. Located between 2 billion and 8 billion light-years away, the galaxies have stellar masses ranging from about 0.3 percent to 100 percent of the mass of our home galaxy.
A paper describing these findings will be published Oct. 20 in The Astrophysical Journal. The Milky Way galaxy must have gone through the same rough-and-tumble evolution as the galaxies in the DEEP2 sample, and gradually settled into its present state as the sun and solar system were being formed.
In the past 8 billion years, the number of mergers between galaxies large and small has decreased sharply. So has the overall rate of star formation and disruptions of supernova explosions associated with star formation. Scientists speculate these factors may play a role in creating the evolutionary trend they observe. Now that astronomers see this pattern, they can adjust computer simulations of galaxy evolution until these models are able to replicate the observed trend. This will guide scientists to the physical processes most responsible for it.
The DEEP2 survey is led by Lick Observatory at the University of California at Santa Cruz in collaboration with the University of California at Berkeley, the University of Hawaii at Manoa, Johns Hopkins University in Baltimore, Md., the University of Chicago and the California Institute of Technology in Pasadena. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Md., conducts Hubble science operations. STScI is operated by the Association of Universities for Research in Astronomy, Inc. in Washington.
Article No.2
NASA must reinvest in nanotechnology research, according to new Rice University paper
The United States may lose its leadership role in space to other countries unless it makes research and development funding and processes - especially in nanotechnology - a renewed and urgent priority, according to a new paper from Rice University's Baker Institute for Public Policy.
The paper, "NASA's Relationship with Nanotechnology: Past, Present and Future Challenges," investigates how NASA has both guided and defunded cutting-edge nanotechnology development since 1996 at its own research facilities and in its collaborations with university scientists and laboratories.
The research was conducted by a team at Rice that included Baker Institute science and technology policy fellow Kirstin Matthews, current Rice graduate student Kenneth Evans and former graduate students Padraig Moloney and Brent Carey. The paper sheds light on a broad field that holds tremendous potential for improving space flight by reducing the weight of spacecraft and developing smaller and more accurate sensors.
This area of research, however, saw a dramatic cutback from 2004 to 2007, when NASA reduced annual nanotechnology R and D expenditures from $47 million to $20 million. NASA is the only U.S. federal agency to scale back investment in this area, the authors found, and it's part of an overall funding trend at NASA.From 2003 to 2010, while the total federal science research budget remained steady between $60 billion and $65 billion (in constant 2012 dollars), NASA's research appropriations decreased more than 75 percent, from $6.62 billion to $1.55 billion.
The authors argue that the agency should restructure, refocus and strengthen its R and D programs."The United States currently lacks a national space policy that ensures the continuity of research and programs that build on existing capabilities to explore space, and that has defined steps for human and robotic exploration of low-Earth orbit, the moon and Mars," Matthews said.
"With Congress and the president wrestling over the budget each year, it is vital that NASA present a clear plan for science and technology R and D that is linked to all aspects of the agency. This includes connecting R and D, with nanotechnology as a lead area, to applications related to the agency's missions."
The authors said that to effectively engage in new technology R and D, NASA should strengthen its research capacity and expertise by encouraging high-risk, high-reward projects to help support and shape the future of U.S. space exploration
"Failure to make these changes, especially in a political climate of flat or reduced funding, poses substantial risk that the United States will lose its leadership role in space to other countries - most notably China, Germany, France, Japan and Israel - that make more effective use of their R and D investments," Matthews said.
Article No.3
ISS Orbit to be adjusted for Next Spacecraft
Specialists of the Moscow Region-based Mission Control Center will on Wednesday carry out a maneuver to readjust the orbit of the International Space Station, a spokesman for the center said.
The readjustment will be carried out with the use of thrusters of the Russian Zvezda service module."The operation is expected to begin at 19:24 Moscow time [15:24 GMT]. The engines of the Zvezda module will operate for 19 seconds," the spokesman said adding that the station's average orbit altitude will be raised by one kilometer to 436 km (270.9 miles).
The reboost is intended to ensure the best conditions for the docking of the Soyuz TMA-06M manned spacecraft with the orbital outpost, slated for October 25.
The Soyuz TMA-06M will bring to the station a new crew, which comprises Russian cosmonauts Oleg Novitsky and Yevgeny Tarelkin, and NASA astronaut Kevin Ford.
Adjustments to the station's orbit are carried out regularly to compensate for the Earth's gravity and to facilitate the successful docking and undocking of spacecraft.
