2007 Feature of the Month Archive

Home computers to help researchers better understand universe

Professor Ben Wandelt's latest project allows people around the world to participate in cutting-edge cosmology research by donating their unused computing cycles.

Want to help unravel the mysteries of the universe? A new distributed computing project designed by a University of Illinois researcher allows people around the world to participate in cutting-edge cosmology research by donating their unused computing cycles.

The project is called Cosmology@Home, and is similar to SETI@Home, a popular program that searches radio telescope data for evidence of extraterrestrial transmissions.

“When you run Cosmology@Home on your computer, it uses part of the computer’s processing power, disk space and network bandwidth,” said project leader Benjamin D. Wandelt, a professor of astronomy and of physics at Illinois.

“Our goal is to search for cosmological models that describe our universe and agree with available astronomical and particle physics data,” Wandelt said.

To achieve this goal, participating computers calculate the observable predictions of millions of theoretical models with different parameters. The predictions are then compared with actual data, including fluctuations in the cosmic microwave background, large-scale distributions of galaxies, and the acceleration of the universe.

In addition to picking out possible models, Cosmology@Home could help design future cosmological observations and prepare for the analysis of future data sets, such as those to be collected by the Planck spacecraft, Wandelt said.

Cosmology@Home is funded by the National Science Foundation. Additional information can be found online at http://cosmologyathome.org/.

Credits: James E. Kloeppel (Illinois News Bureau), Photo by Jerry Thompson, Thompson/McClellan Photography Inc.

CARMA Observes Results of Interstellar Chemistry Near the Orion Nebula

CARMA map of ethyl cyanide (red), dimethyl ether (green), and acetone (black) near the Orion Nebula

Using the newly comissioned Combined Array for Research in Millimeter-Wave Astronomy (CARMA), Illinois astrochemists Douglas Friedel and Professor Lewis Snyder have conducted a high resolution study of the chemistry near the Orion Nebula (also known as Messier 42 and NGC 1976), the closest region of star formation to Earth. They studied the distribution of several molecular species in order to better understand how the different chemicals form in the harsh conditions of interstellar space.

The map at right (click for larger image) shows the spatial distribution of ethyl cyanide [C₂H₅CN] in red, dimethyl ether [(CH₃)₂O] in green and acetone [(CH₃)₂CO] in black. The "+"s denote known infrared sources in the region. Judging by their similar chemical structures, it was expected that acetone and dimethyl ether would form in the same maner. However, the three species do not strongly overlap on the map which indicates that each molecular species forms under different conditions.

Credits: D. Freidel (Illinois)

References: Friedel & Snyder 2007, High Resolution λ=1-mm CARMA Observations of Large Molecules in Orion-KL (accepted for publication in the Astrophysical Journal), arXiv:0709.3232v1

Blowing Cosmic Super Bubbles in the Small Magellanic Cloud

LHa115-N19: A complex of star formation about 200,000 light years from Earth. X-ray (purple); Optical (red); Radio (green)

At a distance of only 200,000 light years, the Small Magellanic Cloud (SMC) is one of the Milky Way's closest galactic neighbors. With its millions of stars, the SMC offers astronomers a chance to study phenomena across the stellar life cycle. In various regions of the SMC, massive stars and supernovas are creating expanding envelopes of dust and gas. Evidence for these structures is found in optical (red) and radio (green) data in this composite image.

An international team led by Illinois astronomer Dr. Rosa Williams used the Chandra X-ray Observatory to peer into one particular region of clouds of gas and plasma where stars are forming. This area, known as LHa115-N19 or N19 for short, is filled with ionized hydrogen gas and it is where many massive stars are expelling dust and gas through stellar winds. When the X-ray data (blue and purple) are combined with the other wavelengths, researchers find evidence for the formation of a so-called superbubble. Superbubbles are formed when smaller structures from individual stars and supernovas combine into one giant cavity.

The Chandra data show evidence for three supernova explosions in this relatively small region. Furthermore, the Chandra observations suggest that each of these supernova remnants were caused by a similar process: the collapse of a very massive star. There are hints that these stars were members of a so-called OB association, a group of stars that formed from the same interstellar cloud.

Credits: NASA/CXC/UIUC/R.Williams et al.; Optical: NOAO/CTIO/MCELS coll.; Radio: ATCA/UIUC/R.Williams et al.

References: Williams et al. 2007, Supernova Remnants in the Magellanic Clouds. VIII. Supernova Remnants in the N19 Complex (submitted to ApJ)

James Kaler New President of the ASP

James B. Kaler

Professor Emeritus of Astronomy James B. Kaler of the University of Illinois at Urbana-Champaign is the new President of the Astronomical Society of the Pacfic, an organization founded in 1889 by a group of Northern California professional and amateur astronomers after joining together to view a rare total solar eclipse. The ASP's earliest purpose was to disseminate astronomical information - a mission which has flourished with astronomers' inexhaustible exploration of the universe. The ASP has become the largest general astronomy society in the world, with members from over 70 nations.

Professor Kaler earned his A.B. at the University of Michigan, his Ph.D. at UCLA, and has been at Illinois since 1964. His research area, in which he has published over 120 papers, involves dying stars. Prof. Kaler has held Fulbright and Guggenheim Fellowships, has been awarded medals for his work from the University of Liege in Belgium and the University of Mexico, gave both the Armand Spitz Lecture to the Great Lakes Planetarium Association and the Margaret Noble Address to the Middle Atlantic Planetarium Society, and received the 2003 Campus Award for Excellence in Public Engagement. He has written for a variety of popular and semi-popular magazines. His latest book is "The Cambridge Encyclopedia of Stars." Prof. Kaler becomes President of the ASP after serving as Vice-President and President-elect.

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Credits: Astronomical Society of the Pacific (Text); photo by Bill Wiegand

Are Fundamental Constants of the Universe Really Constant?

Upper panel: Plot of the size of temperature variations on the sky vs. angular frequency l for the 21 cm signal at different redshifts. Bottom panel: The fractional difference from above if the fine structure constant was 2% less at that time.

One of the fundamental problems in physics is to explain why the fundamental "constants" of the Universe have the values they do and whether or not they are constant in time and space. Recent observations of quasars - starlike objects billions of light-years away - have found a slightly different value for the fine-structure constant (α), which characterizes the strength of the electromagnetic force, billions of years ago.

Using relic radiation from the birth of the universe, University of Illinois astrophysicists Prof. Ben Wandelt and graduate student Rishi Khatri have proposed a new way of measuring α even further in the past, and comparing it with today. "There is a void from about 300,000 years after the Big Bang, when radiation that formed the cosmic microwave background was emitted, to about 500 million years later, when the first stars formed," Wandelt said. "Our measurement technique could probe the fine-structure constant during this period, known as the dark ages."

When a neutral hydrogen atom absorbs a photon of light from the cosmic microwave background, the electron flips its spin. The telltale fingerprint of this atomic transition at a wavelength of 21 cm can serve as a sensitive search for past values of α, said Wandelt and Khatri, who describe their measurement technique in a paper accepted for publication in the journal Physical Review Letters (Vol.98, No.11).

While most radio telescopes are too small to look for variations in α, there are new instruments in the design or construction phase - including the Long Wavelength Array and the Low Frequency Array - that will provide the first limits when brought on line. "The measurements would be tricky, but not impossible," Wandelt said.

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Related Websites:
Summary of Khatri & Wandelt paper

Credits: J. Kloeppel, University of Illinois News Bureau (Text);
R. Khatri & B. Wandelt, Illinois (Image)

First Light Achieved at the South Pole Telescope

The final touches are made to the South Pole Telescope, which became operational in mid-February.

On February 16th, scientists at the South Pole aimed a massive new telescope at Jupiter and successfully collected the instrument's first test observations. Soon, a far more distant quarry will enter the South Pole telescope's (SPT) sights, as a team of researchers, including Professor Joe Mohr from the University of Illinois at Urbana-Champaign, tackles fundamental mysteries of modern cosmology and the nature of the universe: What, for example, is dark energy, the force that dominates the universe?

Astrophysicists know that the universe has been expanding since the Big Bang occurred 13.8 billion years ago. In the late 1990s, astronomers using exploding stars as cosmic tape measures discovered that the expansion of the universe is accelerating. This led them to the idea that dark energy pushes the universe apart, overwhelming gravity, the attractive force exerted by all matter in the universe.

Cold, dry Antarctica will allow SPT to more easily detect the cosmic microwave background (CMB) radiation, the afterglow of the Big Bang, with minimal interference from water vapor. On the electromagnetic spectrum, the CMB falls somewhere between heat radiation and radio waves. The CMB is largely uniform, but it contains tiny ripples of varying density and temperature. These ripples reflect the seeds that, through gravitational attraction, grew into the galaxies and galaxy clusters visible to astronomers today. If dark energy changed the way the universe expanded, it would have left its "fingerprints" in the way it forced galaxies apart over the deep history of time.

The SPT's first key science project will be to study small variations in the CMB to determine if dark energy began to affect the formation of galaxy clusters by fighting against gravity over the past few billion years. SPT can scan large regions of the sky quickly. Scientists expect it to detect thousands, or even tens of thousands, of galaxy clusters within a few years.

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Related Websites:
The South Pole Telescope Web site
Dark Energy Research Group at Illinois

Credits: National Science Foundation (Text); Stephan Meyer, University of Chicago (Image)

Superbubble of supernova remnants caught in act of forming

3-color image showing emission in an optical hydrogen line taken at Cerro-Tololo Inter-American Observatory (red); radio data from the Australia Telescope Compact Array (green); and X-ray emission from the Chandra X-ray Observatory (blue).

From birth to death, massive stars have a tremendous impact on their surroundings. While alive, these stars generate stellar winds that push away nearby gas and dust, forming low-density cavities inside expanding bubbles. When the stars die, shock waves from their death throes can enlarge those bubbles into huge supernova remnants.

This image above shows the "LHA 115-N 19" region in the Small Magellanic Cloud - a galactic neighbor of the Milky Way. This area hosts a number of massive stars, as well as three supernova remnants (marked in the image). "We can tell there has been a fair amount of stellar activity going on." said Rosa Williams, an astronomer at the University of Illinois at Urbana-Champaign.

"In N19, we have not one star, but a number of massive stars blowing bubbles and we have several supernova remnants," Williams said. "The stars are just dispersed enough that their stellar winds and supernova blasts are working together, but have not yet carved out a full cavity. We are witnessing the birth of a superbubble."

Collaborators on the project with Williams are You-Hua Chu, Rosie Chen and Robert Gruendl at Illinois, and Sean Points, an Illinois alumnus, and Chris Smith at the Cerro-Tololo Inter-American Observatory in Chile.

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Credits: James E. Kloeppel, UIUC News Bureau (Text); Rosa Williams, Illinois (Image)

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