Female Astrophysicist Helps Unlock The Secrets Of The Universe

Thursday, April 10, 2008

What do exploding stars, gender equality and Ultimate Frisbee have in common? Usually not much, unless you are Dr Tamara Davis.

The University of Queensland researcher is a new addition to the School of Physical Sciences, where she is using her knowledge of galaxies and supernovae to study the expansion of the Universe.

Dr Davis came to UQ in February after a two-year stint at the University of Copenhagen, Denmark, to work on a project called WiggleZ.

Rather than studying four skivvy-wearing children's entertainers, Dr Davis will be examining the “bumps and wiggles” in the pattern of galaxies we see in the sky and using the findings to measure how quickly the Universe is expanding.

Her project tries to measure the mysterious dark energy that seems to be causing the Universe to expand at an accelerating rate.

Dr Davis said dark energy, jokingly known as “the dark side of the Force”, was a relatively new discovery in astrophysics that cosmologists were still struggling to understand.

The idea that the Universe's expansion is accelerating seems to fly in the face of everything physicists thought they knew about gravity.

“It's as though a ball thrown in the air has accelerated into space instead of falling back to Earth,” Dr Davis said.

“It may mean that Einstein's Theory of Relativity needs revision, or that the Universe is filled with some sort of substance with anti-gravity.”

Dr Davis and the astrophysics team at UQ are trying to figure out which.

While these concepts seem far beyond the realms of everyday, Earth-bound life, Dr Davis said her projects potentially had very practical results.

“We're trying to get down to the nuts and bolts of how the Universe works. At this moment we have no idea how the findings will be relevant to life on Earth but past examples of discoveries like this have resulted in unforeseen applications like electricity and nuclear power,” she said.

“We've got the Universe accelerating without any currently identified energy source, so maybe in the future we will be able to harness this as some sort of green energy to benefit humankind.

“I think the possibility of a clean source of fuel is one of the things that makes this kind of fundamental research worth doing.”

While women are increasingly well represented in many areas of academia, Dr Davis said astrophysics was still a male-dominated field, with just 15% of researchers being female.

“I had been working in the field for about four years and published with about 40 different authors before I published with another female,” she said.

But Dr Davis said her male colleagues have never made her feel “anything but welcome” and she was drawn to astrophysics from her first forays into university study.

“Doing physics gave me the most options, it was a nice, flexible degree,” she said.

“Each step of the way it was the most interesting thing to do so I kept doing it.”

When she's not unlocking the secrets of the Universe, Dr Davis plays Ultimate Frisbee, a non-contact team sport played with a flying disc.

She represented Australia in the sport at the World Championships in Germany in 2000 and Finland in 2004.

Source: University of Queensland

Permalink: http://www.sflorg.com/comm_center/unv_space/p378_22.html

Time Stamp: 4/10/2008 at 10:11:38 PM CST

New Rocky Planet Found In Constellation Leo

Wednesday, April 9, 2008

Spanish and UCL (University College London) scientists have discovered a possible terrestrial-type planet orbiting a star in the constellation of Leo. The new planet, which lies at a distance of 30 light years from the Earth, has a mass five times that of our planet but is the smallest found to date. One full day on the new planet would be equivalent to three weeks on Earth.

The team of astronomers from the Spanish Research Council (CSIC) working with Dr Jean-Philippe Beaulieu, a visiting astrophysicist at UCL, made the discovery from model predictions of a new exoplanet (meaning planet outside our solar system) orbiting a star in the constellation of Leo. Simulations show that the exoplanet, dubbed GJ 436c, orbits its host star (GJ 436) in only 5.2 Earth days, and is thought to complete a revolution in 4.2 Earth days, compared to the Earth’s revolution of 24 hours and full orbit of 365 days. On Earth, a full day (sunset to sunset) coincides quite closely with the rotation period. On the new planet these two periods do not coincide, since the orbital translation period and the rotation period are very similar. For this reason, a full day on the new planet would take four planetary years, or roughly 22 Earth days.

The study, published this week in Astrophysical Journal, predicted the presence of a small exoplanet perturbing an inner planet (already known), producing changes on its orbit. A re-analysis of archival radial velocities also permitted the identification of a signal that perfectly matches the simulations and corresponds to a planet in resonance with the inner one, meaning that for every two orbits of the known planet the new planet completes one.

Ignasi Ribas, lead author of the study from CSIC, says: “After final confirmation, the new exoplanet will be the smallest found to date. It is the first one to be identified from the perturbations exerted on another planet of the system. Because of this, the study opens a new path that should lead to the discovery of even smaller planets in the near future, with the goal of eventually finding worlds more and more similar to the Earth.”

Dr Jean-Philippe Beaulieu, visiting astrophysicist at UCL Physics and Astronomy, says: “This is the fourth super-Earth planet discovered. This planet is the hot twin of the frozen super-Earth (OGLE-2005-BLG-390lb) we discovered by microlensing two years ago. Other previously discovered planets of this class are the two hot super-Earths Gl 581b and Gl 876d detected by their Doppler wobble.“

Dr Giovanna Tinetti, UCL Physics and Astronomy who recently calculated the putative properties of this planet, says: “Calculations indicate that the temperature of the planet could be within 400-700 Kelvin [127-427 Celsius], but it could locally be as low as 350 K [77 C] at the poles, depending on the type of atmosphere.”

Most of the 280 or so planets discovered to date are gas giants similar to Jupiter, although some with masses below 10 times that of the Earth have already been found. Planets with masses of between one and 10 times the Earth are often dubbed super-Earths. In this case, current models predict that the new planet is a rocky type and has a radius some 50 per cent larger than the Earth.

Source: University College London

Permalink: http://www.sflorg.com/comm_center/unv_space/p374_21.html

Time Stamp: 4/9/2008 at 6:39:26 AM CST

New Evidence For Star Formation From Recently Discovered Galaxies

Thursday, April 3, 2008

The strongest burst of star formation occurred two billion years after the Big Bang according to new research led by a Cambridge academic.

Dr Scott Chapman, of the University’s Institute of Astronomy, spoke on Tuesday on new observations from some of the most distant galaxies in the Universe at the Royal Academy of Science (RAS) National Astronomy Meeting in Belfast.

His work has provided evidence for a dramatic surge in star birth within these galaxies, which have only recently been discovered and are so distant that the light we can detect from them has been traveling for 10 billion years. Accordingly, we see them as they were about three billion years after the Big Bang.

They still have large reservoirs of gas, which will power star formation for several hundred million years. Supporting evidence comes from a parallel study by PhD student Caitlin Casey, who found that star formation in these galaxies is distributed over a vast area.

The rate is far higher than anything seen in the present-day Universe, and probably developed after the first stars and galaxies had already formed in what would have been a perfectly smooth Universe. Studying these new objects will give astronomers new insight into the earliest epochs of star formation after the Big Bang.

The recent discovery of a new type of galaxy in this epoch is the key to the new results. The galaxies in question, although very faint in visible light, are much brighter at radio wavelengths.

A related type of galaxy was discovered in 1997 using a new, sensitive camera called SCUBA, which detects radiation at submillimeter wavelengths (longer than visible light, but shorter than radio waves).

In 2004, the Cambridge-led team suggested that the 'submillimeter' galaxies might only represent half of the picture, since SCUBA is intended to pick up colder objects. They suggested that a slightly hotter population of similar galaxies could have gone unnoticed.

Work to search for these galaxies was conducted by an international team of astronomers from the UK, France, Germany and the USA. Observatories around the world, including the UK’s MERLIN array, the Very Large Array and Keck optical telescope in the US, and the Plateau de Bure observatory in France were used to pinpoint them, measure their distances and confirm their star-forming nature through the detection of vastly extended gases and dust.

The new discoveries have allowed for a much more accurate census of some of the most distant galaxies at the peak of their activity. Future observations will look at the details of the galaxies' power source and try to establish how they will develop after their intense bursts of activity come to an end.

The Institute of Astronomy is one of the oldest scientific research departments in the University, with research having been carried out on its site since the 19th century. It works closely on radio astronomy with the Mullard Radio Astronomy Observatory at Cambridge’s Cavendish Laboratory, and on relativity, fluid dynamics and cosmology with groups at the University’s Department of Applied Maths and Theoretical Physics.

Source: University of Cambridge

Permalink: http://www.sflorg.com/comm_center/unv_space/p362_20.html

Time Stamp: 4/3/2008 at 7:51:38 AM CST

Rare Cosmic Rays Are from Far Away

Friday, March 21, 2008

Study Confirms 1966 Prediction: The Most Energetic Particles in the Universe Are Not from the Neighborhood

Final results from the University of Utah's High Resolution Fly's Eye cosmic ray observatory show that the most energetic particles in the universe rarely reach Earth at full strength because they come from great distances, so most of them collide with radiation left over from the birth of the universe.

The findings are based on nine years of observations at the now-shuttered observatory on the U.S. Army's Dugway Proving Ground. They confirm a 42-year-old prediction - known as the Greisen-Zatsepin-Kuzmin (GZK) "cutoff," "limit" or "suppression" - about the behavior of ultrahigh-energy cosmic rays, which carry more energy than any other known particle.

The idea is that most - but not all - cosmic ray particles with energies above the GZK cutoff cannot reach Earth because they lose energy when they collide with "cosmic microwave background radiation,"  which was discovered in 1965 and is the "afterglow" of the "big bang" physicists believe formed the universe 13 billion years ago.

The journal Physical Review Letters published the results Friday, March 21.

The GZK limit's existence was first predicted by Kenneth Greisen of Cornell University while visiting the University of Utah in 1966, and independently by Georgiy Zatsepin and Vadim Kuzmin of Moscow's Lebedev Institute of Physics.

"It has been the goal of much of ultrahigh-energy cosmic ray physics for the past 40 years to find this cutoff or disprove it," says physics Professor Pierre Sokolsky, dean of the University of Utah College of Science and leader of the study by a collaboration of 60 scientists from seven research institutions. "For the first time in 40 years, that question is answered: there is a cutoff."

That conclusion, based on 1997-early 2006 observations at the High Resolution Fly's Eye cosmic ray observatory (nicknamed HiRes) in Utah's western desert, has been bolstered by the new Auger cosmic ray observatory in Argentina. During a cosmic ray conference in Merida, Mexico, last summer, Auger physicists outlined preliminary, unpublished results showing that the number of ultrahigh-energy cosmic rays reaching Earth drops sharply above the cutoff.

So both the HiRes and Auger findings contradict Japan's now-defunct Akeno Giant Air Shower Array (AGASA), which observed roughly 10 times more of the highest-energy cosmic rays - and thus suggested there was no GZK cutoff.

Cosmic Rays: Far Out

Last November, the Auger observatory collaboration - to which Sokolsky also belongs - published a study suggesting that the highest-energy cosmic rays come from active galactic nuclei or AGNs, or the hearts of extremely active galaxies believed to harbor supermassive black holes.

AGNs are distributed throughout the universe, so confirmation that the GZK cutoff is real suggests that if ultrahigh-energy cosmic rays are spewed out by AGNs, they primarily are very distant from the Earth - at least in Northern Hemisphere skies viewed by the HiRes observatory. University of Utah physics Professor Charlie Jui, a co-author of the new study, says that means galaxies beyond our "local" supercluster of galaxies at distances of at least 150 million light years from Earth, or roughly 870 billion billion miles. [In U.S. usage, billion billion is correct here and in subsequent references for 10 to the 18^th power. In British usage, 10 to the 18^th power should be million billion.]

However, unpublished results from HiRes do not find the same correlation that Auger did between ultrahigh-energy cosmic rays and active galactic nuclei. So there still is uncertainty about the true source of extremely energetic cosmic rays.

"We still don't know where they're coming from, but they're coming from far away," Sokolsky says. "Now that we know the GZK cutoff is there, we have to look at sources much farther out."

In addition to the University of Utah, High Resolution Fly's Eye scientists are from Los Alamos National Laboratory in New Mexico, Columbia University in New York, Rutgers University - the State University of New Jersey, Montana State University in Bozeman, the University of Tokyo and the University of New Mexico, Albuquerque.  

Messengers from the Great Beyond

Cosmic rays, discovered in 1912, are subatomic particles: the nuclei of mostly hydrogen (bare protons) and helium, but also of some heavier elements such as oxygen, carbon, nitrogen or even iron. The sun and other stars emit relatively low-energy cosmic rays, while medium-energy cosmic rays come from exploding stars.

The source of ultrahigh-energy cosmic rays has been a mystery for almost a century. The recent Auger observatory results have given the edge to the popular theory they originate from active galactic nuclei. They are 100 million times more energetic than anything produced by particle smashers on Earth. The energy of one such subatomic particle has been compared with that of a lead brick dropped on a foot or a fast-pitched baseball hitting the head.

"Quite apart from arcane physics, we are talking about understanding the origin of the most energetic particles produced by the most energetic acceleration process in the universe," Sokolsky says. "It's a question of how much energy the universe can pack into these extraordinarily tiny particles known as cosmic rays. ... How high the energy can be in principle is unknown. By the time they get to us, they have lost that energy."

He adds: "Looking at energy processes at the very edge of what's possible in the universe is going to tell us how well we understand nature."

Ultrahigh-energy cosmic rays are considered to be those above about 1 billion billion electron volts (1 times 10 to the 18^th power).

The most energetic cosmic ray ever found was detected over Utah in 1991 and carried an energy of 300 billion billion electron volts (3 times 10 to the 20th power). It was detected by the University of Utah's original Fly's Eye observatory, which was built at Dugway during 1980-1981 and improved in 1986.  A better observatory was constructed during 1994-1999 and named the High Resolution Fly's Eye.

Jui says that during its years of operation, HiRes detected only four of the highest-energy cosmic rays - those with energies above 100 billion billion electron volts. AGASA detected 11, even though it was only one-fourth as sensitive as HiRes.

The new study covers HiRes operations during 1997 through 2006, and cosmic rays above the GZK cutoff of 60 billion billion electron volts (6 times 10 to the 19^th power). During that period, the observatory detected 13 such cosmic rays, compared with 43 that would be expected without the cutoff. So the detection of only 13 indicates the GZK limit is real, and that most ultrahigh-energy cosmic rays are blocked by cosmic microwave background radiation so that few reach Earth without losing energy.

The discrepancy between HiRes Fly's Eye and AGASA is thought to stem from their different methods for measuring cosmic rays.

HiRes used multifaceted (like a fly's eye) sets of mirrors and photomultiplier tubes to detect faint ultraviolet fluorescent flashes in the sky generated when incoming cosmic ray particles hit Earth's atmosphere. Sokolsky and University of Utah physicist George Cassiday won the prestigious 2008 Panofsky Prize for developing the method.

HiRes measured a cosmic ray's energy and direction more directly and reliably than AGASA, which used a grid-like array of "scintillation counters" on the ground.

The Search Goes On

University of Tokyo, University of Utah and other scientists now are using the new $17 million Telescope Array cosmic ray observatory west of Delta, Utah, which includes three sets of fluorescence detectors and 512 table-like scintillation detectors spread over 400 square miles - in other words, the two methods that produced conflicting results at HiRes and AGASA. One goal is to figure out why ground detectors gave an inflated count of the number of ultrahigh-energy cosmic rays.

The Telescope Array also will try to explain an apparent shortage in the number of cosmic rays at energies about 10 times lower than the GZK cutoff. This ankle-shaped dip in the cosmic ray spectrum is a deficit of cosmic rays at energies of about 5 billion billion electron volts.

Sokolsky says there is debate over whether the "ankle" represents cosmic rays that run out of "oomph" after being spewed by exploding stars in our galaxy, or the loss of energy predicted to occur when ultrahigh-energy cosmic rays from outside our galaxy collide with the big bang's afterglow, generating electrons and antimatter positrons.

The Telescope Array and Auger observatories will keep looking for the source of rare ultrahigh-energy cosmic rays that evade the big bang afterglow and reach Earth.

"The most reasonable assumption is they are coming from a class of active galactic nuclei called blazars," Sokolsky says.

Such a galaxy center is suspected to harbor a supermassive black hole with the mass of a billion or so suns. As matter is sucked into the black hole, nearby matter is spewed outward in the form of a beam-like jet. When such a jet is pointed at Earth, the galaxy is known as a blazar.

"It's like looking down the barrel of a gun," Sokolsky says. "Those guys are the most likely candidates for the source of ultrahigh-energy cosmic rays."

The new study's 60 co-authors include Sokolsky, Jui and 31 other University of Utah faculty members, postdoctoral fellows and students: Rasha Abbasi, Tareq Abu-Zayyad, Monica Allen, Greg Archbold, Konstantin Belov, John Belz, S. Adam Blake, Olga Brusova, Gary W. Burt, Chris Cannon, Zhen Cao, Weiran Deng, Yulia Fedorova, Richard C. Gray, William Hanlon, Petra Huntemeyer, Benjamin Jones, Kiyoung Kim, the late Eugene Loh, Melissa Maestas, Kai Martens, John N. Matthews, Steffanie Moore, Kevin Reil, Robertson Riehle, Douglas Rodriguez, Jeremy D. Smith, R. Wayne Springer, Benjamin Stokes, Stanton Thomas, Jason Thomas and Lawrence Wiencke.

Source: University of Utah

Permalink: http://www.sflorg.com/comm_center/unv_space/p341_19.html

Time Stamp: 3/21/2008 at 1:54:56 PM CST

Meteorites are Rich in the Building Blocks of Life, Claims New Research

Thursday, March 13, 2008

Amino acids that are the building blocks of life have been found in their highest ever concentration in two ancient meteorites which crashed to Earth millions of years ago, scientists claim today.

Scientists believe their research, published online in the journal Meteoritics and Planetary Science, provides fresh insights into the origins of life on Earth.

Amino acids form the basis of proteins and enzymes, which are the building blocks of all biological life. They have been found in ancient carbon rich meteorites, which are fragments of asteroids formed shortly after the birth of the solar system.

The research team believes that the presence of amino acids in these meteorites provides clear evidence that the early solar system was richer in life's raw materials than previously thought and that these materials may have helped to kick-start life on this planet.

Lead researcher, Dr Zita Martins, from Imperial College London's Department of Earth Science and Engineering, explains:

"We know that approximately 3.8 to 4.5 billion years ago the Earth underwent heavy bombardment from meteorites which brought molecules to our planet, just before life emerged on Earth. However, there is a gap in knowledge about how life came into being. Our work has shown that it may have been meteoritic amino acids and other biologically useful compounds that spurred life into existence."

The team found amino acids in two ancient meteorites called CR chondrites, which were found in Antarctica in the 1990s. By analyzing the carbon content of these meteoritic amino acids, the scientists wearable to determine that, unlike Earth based amino acids which prefer a lighter variety of carbon, their samples were made from a heavier carbon which could only have been formed in space.

Dr Martins says her work provides new insights into the chemistry of the early solar system and the resources available for early life.

"Our increasing understanding of the materials available for the first living systems in the solar system suggests that we are all products of cosmic chemistry," said Dr Martins.

Dr Zita Martins conducted her research whilst based at the Leiden University, Netherlands, in association with the Carnegie Institution of Washington and NASA JPL in the US.

Source: Imperial College London

Permalink: http://www.sflorg.com/comm_center/unv_space/p327_18.html

Time Stamp: 3/13/2008 at 11:08:34 AM CST