Friday, October 29, 2010
The study is the most extensive and sensitive planetary census of its kind. Astronomers used the W.M. Keck Observatory in Hawaii for five years to search 166 sun-like stars near our solar system for planets of various sizes, ranging from three to 1,000 times the mass of Earth. All of the planets in the study orbit close to their stars. The results show more small planets than large ones, indicating small planets are more prevalent in our Milky Way galaxy.
"We studied planets of many masses -- like counting boulders, rocks and pebbles in a canyon -- and found more rocks than boulders, and more pebbles than rocks. Our ground-based technology can't see the grains of sand, the Earth-size planets, but we can estimate their numbers," said Andrew Howard of the University of California, Berkeley, lead author of the new study. "Earth-size planets in our galaxy are like grains of sand sprinkled on a beach -- they are everywhere."
The study appears in the Oct. 29 issue of the journal Science.
The research provides a tantalizing clue that potentially habitable planets could also be common. These hypothesized Earth-size worlds would orbit farther away from their stars, where conditions could be favorable for life. NASA's Kepler spacecraft is also surveying sun-like stars for planets and is expected to find the first true Earth-like planets in the next few years.
Howard and his planet-hunting team, which includes principal investigator Geoff Marcy, also of the University of California, Berkeley, looked for planets within 80-light-years of Earth, using the radial velocity, or "wobble," technique.
They measured the numbers of planets falling into five groups, ranging from 1,000 times the mass of Earth, or about three times the mass of Jupiter, down to three times the mass of Earth. The search was confined to planets orbiting close to their stars -- within 0.25 astronomical units, or a quarter of the distance between our sun and Earth.
A distinct trend jumped out of the data: smaller planets outnumber larger ones. Only 1.6 percent of stars were found to host giant planets orbiting close in. That includes the three highest-mass planet groups in the study, or planets comparable to Saturn and Jupiter. About 6.5 percent of stars were found to have intermediate-mass planets, with 10 to 30 times the mass of Earth -- planets the size of Neptune and Uranus. And 11.8 percent had the so-called "super-Earths," weighing in at only three to 10 times the mass of Earth.
"During planet formation, small bodies similar to asteroids and comets stick together, eventually growing to Earth-size and beyond. Not all of the planets grow large enough to become giant planets like Saturn and Jupiter," Howard said. "It's natural for lots of these building blocks, the small planets, to be left over in this process."
The astronomers extrapolated from these survey data to estimate that 23 percent of sun-like stars in our galaxy host even smaller planets, the Earth-sized ones, orbiting in the hot zone close to a star. "This is the statistical fruit of years of planet-hunting work," said Marcy. "The data tell us that our galaxy, with its roughly 200 billion stars, has at least 46 billion Earth-size planets, and that's not counting Earth-size planets that orbit farther away from their stars in the habitable zone."
The findings challenge a key prediction of some theories of planet formation. Models predict a planet "desert" in the hot-zone region close to stars, or a drop in the numbers of planets with masses less than 30 times that of Earth. This desert was thought to arise because most planets form in the cool, outer region of solar systems, and only the giant planets were thought to migrate in significant numbers into the hot inner region. The new study finds a surplus of close-in, small planets where theories had predicted a scarcity.
"We are at the cusp of understanding the frequency of Earth-sized planets among planetary systems in the solar neighborhood," said Mario R. Perez, Keck program scientist at NASA Headquarters in Washington. "This work is part of a key NASA science program and will stimulate new theories to explain the significance and impact of these findings."
NASA's Exoplanet Science Institute at the California Institute of Technology, Pasadena, Calif., manages time allocation on the Keck telescope for NASA. NASA's Jet Propulsion Laboratory, also in Pasadena, manages NASA's Exoplanet Exploration program office. More information about exoplanets and NASA's planet-finding program is at http://planetquest.jpl.nasa.gov .
Thursday, October 07, 2010
The Greek Ministry of Education, Lifelong Learning and Religious Affairs invites all interested beneficiaries to submit proposal summaries for their inclusion in the Action "Support of Postdoctoral Researchers".
The aim of this Action is to facilitate the acquirement of new research skills by Postdoctoral Researchers (PR) that will promote their career development in any field and/or help them restart their careers after a leave of absence (but no more than seven (7) years following their doctorate conferment date). Emphasis will be given to the support of new scientists at the beginning of their career. The duration of the research projects should range from 24 to 36 months. Each candidate can submit only one (1) research proposal.
The total pubic cost of the present call is 30.000.000€ and it is co-financed by the ESF (European Social Fund). The maximum budget for each project is 150.000€. At least 60% of the total budget should be related to costs pertaining to activities undertaken by the PR and should include a monthly net allowance of 1.600€, subject to cost-of-living adjustments for different countries.
The potential beneficiaries of this call must be either
a) Greek or foreign nationals that have acquired their doctorate from a non-Greek University. These researchers should undertake their research in a University/Research Institution within Greece
b) Greek nationals that have acquired their doctorate from a Greek University. These researchers may undertake their research in a University/Research Institution either in Greece or abroad. In the first case the host Institution should differ from the University where the candidate PR obtained his/her doctorate and the PR should collaborate with a scientist other than his/her PhD supervisor. In the second case the PR should undertake the first 2/3 of his/her research in a University/Research Institution outside Greece and the final 1/3 in a University/Research Institution within Greece.
A two-stage submission procedure will be followed. Please, note that at this stage (i.e. 1st stage) the PRs are not required to have established cooperation with the host Institution. They only need to indicate where (University/Research Institution) and with whom (Faculty member or Research Scientist of a public Research Institution that holds a PhD degree) they would like to cooperate. If a proposal is positively assessed during the evaluation of summaries (1st stage), the respective PR will be asked to submit a full proposal (2nd stage) as well as contact the proposed host Institution to ensure collaboration.
All summaries (as well as the full proposals at the 2nd evaluation stage) will be reviewed by international experts. Further information for the 2nd submission stage will become available in the near future.
All interested beneficiaries should register at the following link:
and submit their summaries at: http://postdoc-ypepth.opengov.gr/
The summaries submission deadline is November 20, 2010 at 22:00 GMT.
Wednesday, October 06, 2010
University of California doctoral programs rank among the best in the nation in a National Research Council report that universities consider the gold-standard assessment of Ph.D. studies. In its first comprehensive evaluation of university doctoral programs since 1995, the NRC reviewed 322 UC programs in science, math, engineering, social sciences and humanities.
In the report, released today (Sept. 28), 141 UC programs were ranked among the top 10 in their fields across a wide range of measures used by the NRC to assess quality.
"I am very proud UC campuses fare so well in these distinguished rankings," said UC President Mark Yudof. "It is clear that the University of California dominates in excellence across a wide range of disciplines. This performance is a function of our outstanding faculty and researchers, talented graduate students, and a diverse and gifted staff and student body."
The NRC, along with the National Academy of Sciences, the National Academy of Engineering and the Institute of Medicine, make up the National Academies, which provide independent science, health and technology policy advice to the U.S. government. The NRC's periodic rankings of American doctoral programs are highly respected among academic institutions.
Program improvement and student guide
The assessment, according to the NRC, is designed to help universities improve the quality of their programs and to provide prospective graduate students with information to help them decide which programs may suit them best.
"The NRC and other ranking tools attest to the fact that UC is the finest public research university system in the nation, if not the world, and that we cannot let the threat of economic uncertainty diminish us in any way," said Yudof.
The new NRC report differs greatly from its previous version in 1995. That report was based mostly on a reputational assessment, with faculty across the United States rating each program, and it provided a top-to-bottom ranking of programs. The 2010 NRC version relies on data from 2005-06, collected from faculty and students. The report uses 20 different variables to rank programs, including research publications by faculty, percentage of students receiving financial support and their time to degree, and student and faculty diversity.
The NRC doesn't list a "best" program, but instead provides several ranges of rankings in which individual programs are likely to fall. A range, for example, can be second best to 12th best in the country.
Overall, the NRC ranked more than 5,000 doctoral programs at 212 U.S. universities.
Top of the class
At nine UC campuses, doctoral programs ranked at the top of their fields. UC's newest campus, UC Merced, was not included because data were collected in 2005-06, before its doctoral programs were fully established.
"The new NRC assessment validates what we and others who evaluate and rank programs have found about the excellence and quality of our graduate programs," said Steven Beckwith, UC vice president for research and graduate studies.
The NRC report is consistent with other recent findings about UC's graduate programs. A UC Office of the President's accountability report, which Beckwith recently presented to the UC Regents, highlighted the following:
- In 2009, UC enrolled 26,117 doctoral students at its 10 campuses.
- As the public institution with primary responsibility for granting doctoral degrees in California, UC awarded 63 percent of all academic doctoral degrees in the state. California led the nation with 5,923 doctorates awarded in 2007-08.
- UC awarded 3,500 Ph.D.s a year — 7 percent of the nation's doctoral degrees.
- In 2009, UC had 7 percent of all the graduate students in the United States, but they won 20 to 30 percent of the most competitive and prestigious fellowships in science, arts and humanities.
"Graduate students play an important role in conducting the research," said Beckwith. "They spark ideas, make discoveries, enrich the arts and work to solve some of society's most pressing problems as they push at the cutting edge of knowledge. They also play a key role in attracting and retaining faculty. Many of our top faculty come to UC because of the outstanding graduate students."
And the faculty themselves, he noted, are distinguished by the top awards and honors they consistently receive.
In the 2009 and 2010 classes elected to the National Academy of Sciences, for example, 66 of the 144 new members came from public universities, and 39 of these were from UC. "Put another way, more than half of the honored scientists from public universities teach and do research at UC," said Beckwith.
The full Data-Based Assessment of Research-Doctorate Programs in the United States report is available online.