A powerful stellar explosion detected March 19 by NASA's Swift satellite has shattered the record for the most distant object that could be seen with the naked eye.
The explosion was a gamma ray burst. Most gamma ray bursts occur when massive stars run out of nuclear fuel. Their cores collapse to form black holes or neutron stars, releasing an intense burst of high-energy gamma rays and ejecting particle jets that rip through space at nearly the speed of light like turbocharged cosmic blowtorches. When the jets plow into surrounding interstellar clouds, they heat the gas, often generating bright afterglows. Gamma ray bursts are the most luminous explosions in the universe since the big bang.
"This burst was a whopper," said Swift principal investigator Neil Gehrels of NASA's Goddard Space Flight Center in Greenbelt, Md. "It blows away every gamma ray burst we've seen so far."
Swift's Burst Alert Telescope picked up the burst at 2:12 a.m. EDT, March 19, and pinpointed the coordinates in the constellation Boötes. Telescopes in space and on the ground quickly moved to observe the afterglow. The burst is named GRB 080319B, because it was the second gamma ray burst detected that day.
Swift's other two instruments, the X-ray Telescope and the Ultraviolet/Optical Telescope, also observed brilliant afterglows. Several ground-based telescopes saw the afterglow brighten to visual magnitudes between 5 and 6 in the logarithmic magnitude scale used by astronomers. The brighter an object is, the lower its magnitude number. From a dark location in the countryside, people with normal vision can see stars slightly fainter than magnitude 6. That means the afterglow would have been dim, but visible to the naked eye.
Later that evening, the Very Large Telescope in Chile and the Hobby-Eberly Telescope in Texas measured the burst's redshift at 0.94. A redshift is a measure of the distance to an object. A redshift of 0.94 translates into a distance of 7.5 billion light years, meaning the explosion took place 7.5 billion years ago, a time when the universe was less than half its current age and Earth had yet to form. This is more than halfway across the visible universe.
"No other known object or type of explosion could be seen by the naked eye at such an immense distance," said Swift science team member Stephen Holland of Goddard. "If someone just happened to be looking at the right place at the right time, they saw the most distant object ever seen by human eyes without optical aid."
GRB 080319B's optical afterglow was 2.5 million times more luminous than the most luminous supernova ever recorded, making it the most intrinsically bright object ever observed by humans in the universe. The most distant previous object that could have been seen by the naked eye is the nearby galaxy M33, a relatively short 2.9 million light-years from Earth.
Analysis of GRB 080319B is just getting underway, so astronomers don't know why this burst and its afterglow were so bright. One possibility is the burst was more energetic than others, perhaps because of the mass, spin, or magnetic field of the progenitor star or its jet. Or perhaps it concentrated its energy in a narrow jet that was aimed directly at Earth.
GRB 080319B was one of four bursts that Swift detected, a Swift record for one day. "Coincidentally, the passing of Arthur C. Clarke seems to have set the universe ablaze with gamma ray bursts," said Swift science team member Judith Racusin of Penn State University in University Park, Pa.
Swift is managed by Goddard. It was built and is being operated in collaboration with Penn State, the Los Alamos National Laboratory, and General Dynamics in the U.S.; the University of Leicester and Mullard Space Sciences Laboratory in the United Kingdom; Brera Observatory and the Italian Space Agency in Italy; plus partners in Germany and Japan.
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NASA Satellite Detects Record Gamma Ray Burst Explosion Halfway Across Universe
WMAP Reveals Neutrinos, End of Dark Ages, First Second of Universe
NASA released this week five years of data collected by the Wilkinson Microwave Anisotropy Probe (WMAP) that refines our understanding of the universe and its development. It is a treasure trove of information, including at least three major findings:
"We are living in an extraordinary time," said Gary Hinshaw of NASA's Goddard Space Flight Center in Greenbelt, Md. "Ours is the first generation in human history to make such detailed and far-reaching measurements of our universe."
WMAP measures a remnant of the early universe - its oldest light. The conditions of the early times are imprinted on this light. It is the result of what happened earlier, and a backlight for the later development of the universe. This light lost energy as the universe expanded over 13.7 billion years, so WMAP now sees the light as microwaves. By making accurate measurements of microwave patterns, WMAP has answered many longstanding questions about the universe's age, composition and development.
The universe is awash in a sea of cosmic neutrinos. These almost weightless sub-atomic particles zip around at nearly the speed of light. Millions of cosmic neutrinos pass through you every second.
"A block of lead the size of our entire solar system wouldn't even come close to stopping a cosmic neutrino," said science team member Eiichiro Komatsu of the University of Texas at Austin.
WMAP has found evidence for this so-called "cosmic neutrino background" from the early universe. Neutrinos made up a much larger part of the early universe than they do today.
Microwave light seen by WMAP from when the universe was only 380,000 years old, shows that, at the time, neutrinos made up 10% of the universe, atoms 12%, dark matter 63%, photons 15%, and dark energy was negligible. In contrast, estimates from WMAP data show the current universe consists of 4.6% percent atoms, 23% dark matter, 72% dark energy and less than 1 percent neutrinos.
Cosmic neutrinos existed in such huge numbers they affected the universe's early development. That, in turn, influenced the microwaves that WMAP observes. WMAP data suggest, with greater than 99.5% confidence, the existence of the cosmic neutrino background - the first time this evidence has been gleaned from the cosmic microwaves.
Much of what WMAP reveals about the universe is because of the patterns in its sky maps. The patterns arise from sound waves in the early universe. As with the sound from a plucked guitar string, there is a primary note and a series of harmonics, or overtones. The third overtone, now clearly captured by WMAP, helps to provide the evidence for the neutrinos.
The hot and dense young universe was a nuclear reactor that produced helium. Theories based on the amount of helium seen today predict a sea of neutrinos should have been present when helium was made. The new WMAP data agree with that prediction, along with precise measurements of neutrino properties made by Earth-bound particle colliders.
Another breakthrough derived from WMAP data is clear evidence the first stars took more than a half-billion years to create a cosmic fog. The data provide crucial new insights into the end of the "dark ages," when the first generation of stars began to shine. The glow from these stars created a thin fog of electrons in the surrounding gas that scatters microwaves, in much the same way fog scatters the beams from a car's headlights.
"We now have evidence that the creation of this fog was a drawn-out process, starting when the universe was about 400 million years old and lasting for half a billion years," said WMAP team member Joanna Dunkley of the University of Oxford in the U.K. and Princeton University in Princeton, N.J. "These measurements are currently possible only with WMAP."
A third major finding arising from the new WMAP data places tight constraints on the astonishing burst of growth in the first trillionth of a second of the universe, called "inflation", when ripples in the very fabric of space may have been created. Some versions of the inflation theory now are eliminated. Others have picked up new support.
"The new WMAP data rule out many mainstream ideas that seek to describe the growth burst in the early universe," said WMAP principal investigator, Charles Bennett, of The Johns Hopkins University in Baltimore, Md. "It is astonishing that bold predictions of events in the first moments of the universe now can be confronted with solid measurements."
The five-year WMAP data were released this week, and results were issued in a set of seven scientific papers submitted to the Astrophysical Journal. For further information, see
Prior to the release of the new five-year data, WMAP already had made a pair of landmark finds. In 2003, the probe's determination that there is a large percentage of dark energy in the universe erased remaining doubts about dark energy's very existence. That same year, WMAP also pinpointed the 13.7 billion year age of the universe.
Additional WMAP science team institutions are: the Canadian Institute for Theoretical Astrophysics, Columbia University, University of British Columbia, ADNET Systems, University of Chicago, Brown University, and UCLA.
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NASA Know-How Helps Athletes Rocket Through Water
When a swimsuit manufacturer wanted to create a better fabric for competitive swimmers, it sought out some unlikely experts -- aerospace engineers at NASA's Langley Research Center in Hampton.
NASA has decades of experience in fluid dynamics and drag reduction. However, aerospace engineers usually concentrate on the element through which airplanes and spacecraft fly, not the liquid through which swimmers travel. Still, some of the science is similar.
"Air and water are both what are referred to as Newtonian fluids," said Steve Wilkinson, a researcher at Langley's Fluid Physics and Control Branch. "Air has different fluid properties than water, including lower density and viscosity, but it still obeys the same physical laws of motion."
That fact led Warnaco Inc. of New York, the U.S. licensee of the Speedo swimwear brand, to seek use of a NASA wind tunnel at Langley to test swimsuit fabrics that may be used by athletes in international competitions.
"We evaluated the surface roughness effects of nearly 60 fabrics or patterns in our small low-speed tunnel, which is perfect for this purpose," Wilkinson said. "We were assessing which fabrics and weaves had the lowest drag."
Reducing drag helps planes fly more efficiently, and reducing drag helps swimmers go faster. Studies indicate viscous drag, or skin friction, is about one-third of the total restraining force on a swimmer. Wind tunnel tests measure the drag on the surface of the fabrics.
Wilkinson and other NASA researchers usually spend their time studying drag reduction for airplanes. They even have worked on drag reduction technology for boats, including an America's Cup winner in the 1980s. This expertise is one reason Speedo chose to work with NASA.
"This is the first time I've tested a fabric and there were some challenges involved," said Wilkinson. "I think we've done a really good job with the help of Speedo in coming up with a protocol that enables us to test these fabrics with ease and precision."
The materials tested come in the form of tubes. Wilkinson stretches the tubes over a smooth, flat aluminum plate and then secures the edges with smooth metal rails and tape to form a precise rectangular model shape. Wilkinson runs the material through a number of wind speeds and, with the help of sensors, measures drag on the surface. Under a reimbursable agreement, NASA turns the wind tunnel data over to Speedo for their use.
"It turns out to simulate a swimmer in the water at about two meters per second, we need to run the wind tunnel at about 28 meters per second, which is well within its capability," Wilkinson added. "The tests generally have shown the smoother the fabric, the lower the drag."
Speedo International's research and development team, Aqualab, took those results and used them to help create a new swimsuit the company says is its most hydro-dynamically advanced to date.
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Mysterious X-ray source in nearby galaxy
Astronomers studying a nearby galaxy have spied a rare type of star system -- one that contains a black hole that suddenly began glowing brightly with X-rays.
Though this type of star system is supposed to be rare, it's the second such system discovered in that galaxy, called Centaurus A.
The discovery suggests that astronomers have more to learn about the lives and deaths of massive stars in galaxies such as our own.
Normally when astronomers study Centaurus A, it's the giant X-ray jets emanating from the heart of the galaxy that steal the show, explained Gregory Sivakoff, a postdoctoral researcher in astronomy at Ohio State University. The jets extend from the galaxy for 13,000 light years in different directions.
But when his team studied Centaurus A with NASA's Chandra X-ray Observatory starting in March 2007, they saw a new X-ray source -- much smaller than the X-ray jets, but still glowing brightly. The source wasn't there during the last survey of the galaxy in 2003, but it shined throughout the time of the new observations, from March to May of 2007.
Because it hadn't been seen before, the astronomers classified the object as a “transient” X-ray source, meaning that the object had been there before 2007, but had only recently brightened enough to stand out.
Sivakoff discussed the results in a press briefing Wednesday, January 9, 2008 at the American Astronomical Society meeting in Austin, Texas.
The newly bright object, dubbed CXOU J132518.2-430304, is most likely a binary star system, the researchers concluded. The two stars likely formed at the same time, with one much more massive than the other. The more massive star evolved more quickly, and collapsed to form a black hole. It is now slowly devouring its companion. Such binary systems are thought to be extremely rare.
But this is the second bright, transient X-ray binary system discovered in Centaurus A -- and that's the problem, Sivakoff said.
“When we look at other galaxies like Centaurus A, we don't see these bright, transient X-ray binaries,” he said. “But now we've found two such objects in Centaurus A, and the implication is that we may not understand these objects as well as we thought we did.”
“So right now, our discovery is actually pointing to a puzzle rather than a solution.”
Because Centaurus A is near to our galaxy, astronomers have long hoped to use it as a Rosetta stone for studying other galaxies with black holes.
As astronomers piece together an explanation for the existence of the newly-discovered binary system, they may gain a better understanding of how black holes form from massive stars and how binary systems evolve.
“These binary systems are signposts of the massive stars that once existed in galaxies like Centaurus A. To understand the massive stars, we must first know how to read the signs,” he said.
Sivakoff and Ralph Kraft of the Harvard-Smithsonian Center for Astrophysics led the study; their collaborators were from NASA Goddard Space Flight Center, Oak Ridge Associated Universities, University of Hertfordshire, University of Virginia, University of Bristol, McMaster University, and the University of
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