SpaceJibe

February 11, 2016

Scientists find evidence of gravitational waves predicted by Einstein

Filed under: Big Bang, Black Holes, Cool, Cosmology, Gamma Ray Bursts — bferrari @ 11:54 am
File image - An image from a simulation showing how matter might be moved around in the extreme environment around a black hole. (Özel/Chan) (Özel/Chan)

File image – An image from a simulation showing how matter might be moved around in the extreme environment around a black hole. (Özel/Chan) (Özel/Chan)

After decades of searching, scientists announced Thursday that they have detected gravitational waves which are ripples in the fabric of space-time that were predicted by Einstein.

 

An international team of astrophysicist said that they detected the waves from the distant crash of two black holes, using a $1.1 billion instrument. The Ligo Collaboration was behind the discovery and it has been accepted for publication in the journal Physical Review Letters.

Related: Meteorite probably didn’t kill man in India, NASA says

“We have detected gravitational waves,” Caltech’s David H. Reitze, executive director of the LIGO Laboratory, told journalists at a news conference in Washington DC.

The news, according to the Associated Press, is being compared by at least one theorist to Galileo taking up a telescope and looking at the planets and the biggest discovery since the discovery of the Higgs particle. It has stunned the world of physics and astronomy, prompting scientists to say it the beginning of a new era in physics that could lead to scores more astrophysical discoveries and the exploration of the warped side of the universe.

“Our observation of gravitational waves accomplishes an ambitious goal set out over five decades ago to directly detect this elusive phenomenon and better understand the universe, and, fittingly, fulfills Einstein’s legacy on the 100th anniversary of his general theory of relativity,” Reitze said in a statement.

Related: Hundreds of hidden galaxies glimpsed behind Milky Way

The discovery confirms a major prediction of Albert Einstein’s 1915 general theory of relativity. Gravitation waves carry information about their dramatic origins and about the nature of gravity that cannot be obtained from elsewhere.

Not only have they fascinated by scientist by found their way into pop culture – namely through movies such as “Back To The Future,” where the space-time continuum was used a medium for the DeLorean time machine to go back in time. It also featured in the “Terminator” series.

Their existence was first demonstrated in the 1970s and 1980s by Joseph Taylor, Jr., and colleagues. In 1974, Taylor and Russell Hulse discovered a binary system composed of a pulsar in orbit around a neutron star. Taylor and Joel M. Weisberg in 1982 found that the orbit of the pulsar was slowly shrinking over time because of the release of energy in the form of gravitational waves. For discovering the pulsar and showing that it would make possible this particular gravitational wave measurement, Hulse and Taylor were awarded the 1993 Nobel Prize in Physics.

Related: White House proposes $19 billion NASA budget

In the latest breakthrough, the gravitational waves were detected on Sept. 14, 2015 by both of the twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington.

Based on the observed signals, LIGO scientists estimate that the black holes for this event were about 29 and 36 times the mass of the sun, and the event took place 1.3 billion years ago. About three times the mass of the Sun was converted into gravitational waves in a fraction of a second — with a peak power output about 50 times that of the whole visible universe.

By looking at the time of arrival of the signals — the detector in Livingston recorded the event 7 milliseconds before the detector in Hanford — scientists can say that the source was located in the Southern Hemisphere.

Related: New star puts on a show in stunning image

According to general relativity, a pair of black holes orbiting around each other lose energy through the emission of gravitational waves, causing them to gradually approach each other over billions of years, and then much more quickly in the final minutes. In a final fraction of a second, the two black holes collide and form one massive black hole. A portion of their combined mass is converted to energy, according to Einstein’s formula E=mc2, and this energy is emitted as a final strong burst of gravitational waves.

These are the gravitational waves that LIGO observed.

“With this discovery, we humans are embarking on a marvelous new quest: the quest to explore the warped side of the universe — objects and phenomena that are made from warped spacetime. Colliding black holes and gravitational waves are our first beautiful examples,” Caltech’s Kip Thorne said.

 

Source

January 16, 2016

Astronomers may have found most powerful supernova

Filed under: Big Bang, Black Holes, Cool, Cosmology, Gamma Ray Bursts, Supernova — bferrari @ 4:51 pm
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Enter a caption

  • “This may be the most powerful supernova ever seen by anybody,” Ohio State University professor says

An international team of astronomers may have discovered the biggest and brightest supernova ever.

The explosion was 570 billion times brighter than the sun and 20 times brighter than all the stars in the Milky Way galaxy combined, according to a statement from The Ohio State University, which is leading the study. Scientists are straining to define its strength.

“This may be the most powerful supernova ever seen by anybody … it’s really pushing the envelope on what is possible,” study co-author Krzysztof Stanek, an astronomer at Ohio State, was quoted as saying in The Los Angeles Times.

The team of astronomers released their findings this week in the journal Science. The explosion and a gas cloud that resulted are called ASASSN-15lh after the team of astronomers, All Sky Automated Survey for Supernovae, that discovered it last June.

A supernova is a rare and often dramatic phenomenon that involves the explosion of most of the material within a star. Supernovas can be very bright for a short time and usually release huge amounts of energy.

Searching for the power source

This blast created a massive ball of hot gas that the astronomers are studying through telescopes around the world, Ohio State said. It cannot be seen with the naked eye because it is 3.8 billion light years from Earth.

There’s an object about 10 miles across in the middle of the ball of gas that astronomers are trying to define.

“The honest answer is at this point that we do not know what could be the power source for ASASSN-15lh,” said Subo Dong, lead author of the Science paper, according to Ohio State. He is a Youth Qianren Research Professor of astronomy at the Kavli Institute for Astronomy and Astrophysics at Peking University.

Todd Thompson, professor of astronomy at Ohio State, said the object in the center may be a rare type of star called a millisecond magnetar. Spawned by a supernova, it’s a rapidly spinning, dense star with a powerful magnetic field.

Could it be a ‘supermassive black hole’?

To achieve the brightness recorded, the magnetar would have to spin 1,000 times a second and “convert all that rotational energy to light with nearly 100% efficiency,” Thompson said, according to the Ohio State press release. “It would be the most extreme example of a magnetar that scientists believe to be physically possible.”

The question of whether a suprnova truly caused the space explosion may be settled later this year with help from the Hubble Space Telescope, which will allow astronomers to see the host galaxy surrounding the object in center of the ball of gas, Ohio State said.

If it’s not a magnetar, it may be unusual nuclear activity around “a supermassive black hole,” Ohio State said.

Source

May 23, 2014

Supernova discovery reveals how the biggest, brightest stars die

Filed under: Black Holes, Cool, Gamma Ray Bursts — bferrari @ 11:28 am
A brilliant supernova (right) explodes in the galaxy UGC 9379, located about 360 million light-years from Earth, in this before-and-after view. The left image was taken by the Sloan Digital Sky Survey, while the right image was obtained with aAVISHAY GAL-YAM, WEIZMANN INSTITUTE OF SCIENCE

A brilliant supernova (right) explodes in the galaxy UGC 9379, located about 360 million light-years from Earth, in this before-and-after view. The left image was taken by the Sloan Digital Sky Survey, while the right image was obtained with aAVISHAY GAL-YAM, WEIZMANN INSTITUTE OF SCIENCE

The most massive and luminous stars were long suspected to explode when they die, and astronomers now have the most direct evidence yet that these cosmic behemoths go out with a bang.

These findings shed light on the star explosions that provide the universe with the ingredients for planets and life, the researchers added.

With a mass more than 330,000 times that of Earth, the sun accounts for 99.86 percent of the solar system’s total mass. But as stars go, the sun is a lightweight. The largest and most luminous stars in the universe are Wolf-Rayet stars, which are more than 20 times as massive as the sun and at least five times as hot. Only a few hundred of these titan stars are known to astronomers.

[Biggest Star Mysteries of All Time]

The intense heat of Wolf-Rayet stars forces their matter apart, making them extraordinarily windy stars. They usually lose the mass equivalent to that of the Earth each year, blowing winds at up to 5.6 million mph.

How giant stars die

Astronomers long suspected that Wolf-Rayet stars violently self-destructed as supernovas, the most powerful stellar explosions in the universe. These outbursts are bright enough to momentarily outshine their entire galaxies, and enrich galaxies with heavy elements that eventually become the building blocks for planets and life.

However, the gigantic amounts of matter these stars blow out usually obscure them completely, so scientists weren’t sure how they form, live and die.

“Finding what kind of star exploded, after it already exploded, is, of course, a hard problem, since the explosion destroys much of the information,” said study author Avishay Gal-Yam, an astrophysicist at the Weizmann Institute of Science in Israel.

Some researchers even raised doubts as to whether Wolf-Rayet stars detonated as supernovas at all. “Some modelers predict that massive Wolf-Rayet stars will collapse into a black hole ‘quietly,’ without making a luminous supernova,” Gal-Yam told Space.com.

Now, for the first time, scientists have direct confirmation that a Wolf-Rayet star died in a supernova. They detail their findings in the May 22 issue of the journal Nature.

The researchers focused on a supernova named SN 2013cu, which exploded about 360 million light-years away from Earth in the Bootes constellation. This explosion was a Type IIb supernova, meaning it took place after the core of its star ran out of fuel, collapsing into an extraordinarily dense nugget in a fraction of a second and rebounding with a blast outward. What is left over after such supernovas is either a neutron star or a black hole.

A Wolf-Rayet smoking gun

By surveying the sky with the intermediate Palomar Transient Factory (iPTF), a project that charts the sky with a telescope mounted with a robotic observing system, the researchers discovered the supernova very soon after it happened.

“We now send high-quality supernova alerts to astronomers all around the globe in less than 40 minutes,” said study co-author Peter Nugent, a researcher at the University of California, Berkeley.

The scientists next rallied ground- and space-based telescopes across the world to observe the infant supernova approximately 5.7 hours and 15 hours after it detonated.

“Newly developed observational capabilities now enable us to study exploding stars in ways we could only dream of before,” Gal-Yam said. “We are moving towards real-time studies of supernovae.”

The explosion ionized surrounding molecules in an ultraviolet flash, giving them an electric charge. The ionized material that surrounded the star emits light that “tells us the elemental composition of the wind, and hence the surface composition of the star as it was just before it exploded,” Gal-Yam said. “That is a very powerful clue about the nature of the exploding star and how it evolved before it exploded, and this is the first time we managed to get this information.”

That opportunity lasts only for a day before the supernova blast wave sweeps the ionization away, Gal-Yam added.

This light suggested the precursor of the supernova was a nitrogen-rich Wolf-Rayet star. “This is the smoking gun,” Nugent said. “For the first time, we can directly point to an observation and say that this type of Wolf-Rayet star leads to this kind of Type IIb supernova.”

“When I identified the first example of a Type IIb supernova in 1987, I dreamed that someday we would have direct evidence of what kind of star exploded,” said study co-author Alex Filippenko, a researcher at the University of California, Berkeley. “It’s refreshing that we can now say that Wolf-Rayet stars are responsible, at least in some cases.”

Future studies could analyze more Wolf-Rayet stars, to see if these violent deaths are standard for them.

“If we can show that this is the norm for such massive stars, it would mean that new theories will have to be developed to explain how you can make a black hole and still throw out a lot of material and a lot of energy to make a luminous supernova,” Gal-Yam said.

Source

October 28, 2013

Coldest Known Object In Space Reveals Its Ghostly Figure

Filed under: Big Bang, Cool, Cosmology, Gamma Ray Bursts, Supernova — bferrari @ 5:55 pm
Image Caption: The Boomerang Nebula reveals its true shape with ALMA. The background blue structure, as seen in visible light (HST), shows a classic double-lobe shape with a very narrow central region. ALMA’s ability to see the cold molecular gas reveals the nebula’s more elongated shape, in red. (FULL IMAGE) (Bill Saxton; NRAO/AUI/NSF; NASA/Hubble; Raghvendra Sahai)

Image Caption: The Boomerang Nebula reveals its true shape with ALMA. The background blue structure, as seen in visible light (HST), shows a classic double-lobe shape with a very narrow central region. ALMA’s ability to see the cold molecular gas reveals the nebula’s more elongated shape, in red. (FULL IMAGE) (Bill Saxton; NRAO/AUI/NSF; NASA/Hubble; Raghvendra Sahai)

The Boomerang Nebula, at a crisp one degree Kelvin (-458 degrees Fahrenheit), is the coldest known object in the Universe. In fact, the Boomerang Nebula is colder than the faint afterglow of the Big Bang, which is the natural background temperature of space.

To learn more about this intriguing object, a team of astronomers used the Atacama Large Millimeter/submillimeter Array (ALMA) telescope to investigate its frigid properties and determine its true shape, which is eerily ghost-like.

The nebula appeared lopsided when originally observed with ground-based telescopes. This lopsidedness is how this nebula got its name. A bow-tie-like structure was revealed when astronomers later used Hubble Space Telescope observations. According to the new ALMA observations, the Hubble data only told part of the story. The twin lobes seen in the Hubble image may actually be a trick of the light as seen at visible wavelengths.

“This ultra-cold object is extremely intriguing and we’re learning much more about its true nature with ALMA,” saidRaghvendra Sahai, a researcher and principal scientist at NASA’s Jet Propulsion Laboratory (JPL). “What seemed like a double lobe, or ‘boomerang’ shape, from Earth-based optical telescopes, is actually a much broader structure that is expanding rapidly into space.”

The results of this study were published in the Astrophysical Journal.

Located approximately 5,000 light-years away in the constellation Centaurus, the Boomerang Nebula is a relatively young example of an object known as a planetary nebula. Contrary to their name, planetary nebulae are actually the end-of-life phases of stars like our Sun that have sloughed off their outer layers. The remaining centers are white dwarf stars, emitting intense ultraviolet radiation that causes the gas in the nebulae to glow and emit light in brilliant colors.

The Boomerang is an example of a pre-planetary nebula, which is a stage in a star’s life immediately preceding the planetary nebula phase. At this point, the central star is not yet hot enough to emit enough electrical ultraviolet radiation to produce its characteristic glow. A pre-planetary nebula is seen by starlight reflecting off its dust grains.

The gas outflow from the Boomerang Nebula’s star is expanding rapidly and cooling itself in the process, in a way similar in principle to the way refrigerators use expanding gas to produce cold temperatures. The astronomers were able to gauge the temperature of the gas in the nebula by seeing how it absorbed the cosmic microwave background radiation, which has a very uniform temperature of 2.8 degrees Kelvin (-455 degrees Fahrenheit).

“When astronomers looked at this object in 2003 with Hubble, they saw a very classic ‘hourglass’ shape,” commented Sahai. “Many planetary nebulae have this same double-lobe appearance, which is the result of streams of high-speed gas being jettisoned from the star. The jets then excavate holes in a surrounding cloud of gas that was ejected by the star even earlier in its lifetime as a red giant.”

Single-dish millimeter wavelength telescopes, however, did not detect the narrow waist observed by the Hubble. Rather, they found a more uniform and nearly spherical outflow of material.

ALMA has unprecedented resolution, which allowed the astronomers to reconcile the discrepancy. The team was able to detect the double-lobe structure that is seen in the Hubble image, but only in the inner regions of the nebula, by observing the distribution of carbon monoxide molecules, which glow brightly at millimeter wavelengths. A more elongated cloud of cold gas that is roughly round was observed farther out.

A dense lane of millimeter-sized dust grains were found to be surrounding the star, providing an explanation for why the outer cloud has an hourglass shape in visible light. The dust grains form a mask that shade a portion of the central star, allowing its light to leak out in narrow but opposite directions in the cloud. This forms the hourglass appearance.

“This is important for the understanding of how stars die and become planetary nebulae,” said Sahai. “Using ALMA, we were quite literally and figuratively able to shed new light on the death throes of a Sun-like star.”

The current findings also suggest that the outer fringes of the nebula are beginning to warm, even though they are slightly colder than the cosmic microwave background. The warming could be caused by the photoelectric effect — an effect first proposed by Albert Einstein in which light is absorbed by solid material, which then re-emits electrons.

 

Largest Known Star Self-Destructs While Astronomers Observe

Filed under: Cool, Gamma Ray Bursts, Supernova — bferrari @ 5:35 pm
(European Southern Observatory)

(European Southern Observatory)

A group of international scientists have been observing as the largest known star in the Universe tears itself apart.

Astronomers from the UK, Chile, Germany and the US have watched as W26 in the Westerlund 1 star cluster shed its outer layers and flings a huge cloud of glowing hydrogen gas out to return enriched material back to the interstellar medium.

The latest observation, reported in the journal Monthly Notices of the Royal Astronomical Society, is considered to be a vital step in understanding how massive stars help enrich the space between stars, which is necessary for forming planetary systems.

Westerlund 1 is the most massive cluster of stars in the Milky Way galaxy. The cluster, which is 16,000 light years away from Earth, is home to several hundred thousand stars. Astronomers used the Very Large Telescope (VST) at the European Southern Observatory’s Paranal Observatory in Chile to observe Westerlund 1 when they happened to discover W26.

They realized that the star was probably the largest ever discovered, with a radius 1,500 times larger than our Sun. They also discovered that W26 is one of the most luminous red supergiants ever seen.

Glowing hydrogen-gas clouds like the one seen around W26 are rarely found around massive stars, and are even rarer around red supergiants. This was the first ionized nebula ever discovered around such a star. While W26 is too cool to make the gas glow, the astronomers believe the source of the ionizing radiation could be either hot blue stars or possibly a companion star.

The nebula around W26 is similar to the nebula surrounding SN1987A, which is the remnant of a star that exploded as a supernova in 1987. SN1987A was the closest observed supernova to Earth since 1604, and it gave astronomers a chance to better understand the properties of these explosions.

Astronomers will be able to use the new nebula around W26 to better understand the mass loss processes around massive stars. Stars with masses tens of times larger than the Sun live very short and dramatic lives, with some having lifetimes of less than a few million years before they exhaust all of their nuclear fuel and explode as a supernova.

When a massive star reaches the end of its life it becomes highly unstable, ejecting a considerable amount of material from its outer envelopes. This material has been enriched by nuclear reactions deep within the star and includes many of the elements necessary for forming rocky planets like Earth. Knowing more about how this material is ejected and how it affects the evolution of the star would enable scientists to better understand the evolution of our universe.

Source

 

March 17, 2013

6 Mind Blowing Things Nobody Taught You About Black Holes

Filed under: Big Bang, Black Holes, Cool, Cosmology, Gamma Ray Bursts, Supernova, Wierd — bferrari @ 7:02 pm

Black holes are what happens when the universe divides by zero and eats anything that tries to notice. They’re cosmological grizzly bears: an inevitable result of nature that is majestic and terrifying to every species intelligent enough to comprehend them.

Black holes happen when reality has an overflow error: you put too much stuff in one place, and it breaks both the stuff and the place with gravity. Gravity is usually the responsible older sibling of the universe, always pulling things together. Black holes are where gravity goes full Al Capone, calls a meeting of all the fundamental forces of existence and makes a big showy spectacle of crushing them. It doesn’t just crush matter; it crushes the quantum laws that define matter, stomps them all into a compacted nugget until matter stops existing so much. It simply overrides reality.

And yet, most people treat them like cosmic vacuum cleaners. Science fiction characters are worse at understanding black holes than they are at aiming laser weapons, and the coverage they get in most schools only encourage students to kill themselves with trampolines and bowling balls. That’s a shame, since black holes are literally the ultimate everything, so we’re looking at how cool they are.

#6. They’re the Brightest Things in the Sky

“Black hole” is as simple and descriptive a title as “Pied Piper of Hamelin,” and equally misleading. The one thing everybody knows about black holes is that not even light can escape, meaning they’re pictured as the interstellar equivalent of open manhole covers: pitch-black doom awaiting the unwary. But black holes are often the brightest points in the sky.

A black hole.

A black hole.

What people forget is that while there is an “event horizon” boundary inside of which light can’t escape, there’s also an “entire rest of the universe” where it can, often in galaxy-blinding quantities. When a rotating black hole consumes a cloud of interstellar gas, the material is drawn into a spiral, like fluid swirling down the plughole of existence … which is actually what’s cosmologically happening.

The hair around the universe's plughole is ENTIRE GALAXIES.

The hair around the universe’s plughole is ENTIRE GALAXIES.

Meteors light up because a thin layer of gas is being compressed by plummeting space rock and further heated by friction. When gas clouds fall into a black hole, the whole thing is being compressed, plummeting, and being heated by friction. The consumed cloud is its own meteor and atmosphere, and both are burning with cosmic fire. They get so hot, they don’t just glow white, they glow X-ray, converting 10 percent of their total mass into pure energy. For comparison, fusion warheads only convert 0.5 percent of their mass into energy. Understand: Black holes create a place where dropping something releases 20 times more energy than thermonuclear detonation. And our galaxy’s central black hole, Sagittarius A*, will be doing that this year.
Black holes can glow so brightly that they defeat their own gravity. Supermassive black holes can reach the Eddington limit, where continuum radiation force defeats the otherwise irresistible gravitational attraction. (That sentence contains more band names and anime series subtitles than anything else I’ve ever written.) The radiation becomes so intense that it blows away the incoming material. And this isn’t radiation as in “nuclear”; this is radiation as in “light.” As in “move toward the light, except in the real heavens, the light can be so intense that it shoves you back.”

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January 12, 2013

Largest structure in universe discovered

Filed under: Big Bang, Black Holes, Cool, Cosmology, Gamma Ray Bursts — bferrari @ 12:07 pm
Light from the most distant quasar yet seen reveals details about the chemistry of the early universe. (ESO/M. Kornmesser)

Light from the most distant quasar yet seen reveals details about the chemistry of the early universe. (ESO/M. Kornmesser)

Astronomers have discovered the largest known structure in the universe, a clump of active galactic cores that stretches 4 billion light-years from end to end.

The structure is a large quasar group (LQG), a collection of extremely luminous galactic nuclei powered by supermassive central black holes. This particular group is so large that it challenges modern cosmological theory, researchers said.

“While it is difficult to fathom the scale of this LQG, we can say quite definitely it is the largest structure ever seen in the entire universe,” lead author Roger Clowes, of the University of Central Lancashire in England, said in a statement. “This is hugely exciting, not least because it runs counter to our current understanding of the scale of the universe.”

 

‘This is hugely exciting, not least because it runs counter to our current understanding of the scale of the universe.’

– Roger Clowes, of the University of Central Lancashire in England

 

Quasars are the brightest objects in the universe. For decades, astronomers have known that they tend to assemble in huge groups, some of which are more than 600 million light-years wide.

But the record-breaking quasar group, which Clowes and his team spotted in data gathered by the Sloan Digital Sky Survey, is on another scale altogether. The newfound LQC is composed of 73 quasars and spans about 1.6 billion light-years in most directions, though it is 4 billion light-years across at its widest point.

 

To put that mind-boggling size into perspective, the disk of the Milky Way galaxy — home of Earth’s solar system — is about 100,000 light-years wide. And the Milky Way is separated from its nearest galactic neighbor, Andromeda, by about 2.5 million light-years.

The newly discovered LQC is so enormous, in fact, that theory predicts it shouldn’t exist, researchers said. The quasar group appears to violate a widely accepted assumption known as the cosmological principle, which holds that the universe is essentially homogeneous when viewed at a sufficiently large scale.

Calculations suggest that structures larger than about 1.2 billion light-years should not exist, researchers said.

“Our team has been looking at similar cases which add further weight to this challenge, and we will be continuing to investigate these fascinating phenomena,” Clowes said.

The new study was published Jan. 11 in the Monthly Notices of the Royal Astronomical Society.

Source

November 1, 2012

Light from universe’s first stars seen

Nov. 1, 2012: Ultraviolet and visible light emitted by all the stars that ever existed is still coursing through the universe. Astronomers refer to this "fog" of starlight as the extragalactic background light (EBL). (NASA's Goddard Space Flight Center)

Nov. 1, 2012: Ultraviolet and visible light emitted by all the stars that ever existed is still coursing through the universe. Astronomers refer to this “fog” of starlight as the extragalactic background light (EBL). (NASA’s Goddard Space Flight Center)

Astronomers have spotted light from the very first stars in the universe, which are almost as old as time itself.

Shortly after the Big Bang 13.7 billion years ago, the universe cooled enough to let atoms form, which eventually clumped together to create the first stars. Ever since these stars ignited, their light has been filling the universe, creating a pervasive glow throughout space that each successive generation of stars adds to.

Now, astronomers have detected this glow — called the extragalactic background light, or EBL — and have separated out the light from later stars, isolating the contribution from the first stars that ever existed.

“The EBL is the ensemble of photons generated by all the stars and also all the black holes in the universe,” said astrophysicist Marco Ajello of the SLAC National Accelerator Laboratory in California, who led the research. “The EBL also includes the light of the first massive stars that ever shone. We have a fairly good knowledge of the light emitted by ‘normal’ stars. Thus, by measuring the EBL we are able to constrain the light of the first stars.”

‘By measuring the extragalactic background light, we are able to constrain the light of the first stars.’

– astrophysicist Marco Ajello of the SLAC National Accelerator Laboratory

Ajello and his team did not measure the EBL directly, but they detected it by analyzing measurements of distant black holes made by NASA’s Fermi Gamma-Ray Space Telescope. Fermi studied light from objects called blazars, which are giant black holes that release copious amounts of light while gobbling up large meals of matter.

“We use [blazars] as cosmic lighthouses,” Ajello said. “We observe their dimming due to the EBL ‘fog’. This allows us to quantify how much EBL there is between us and the blazars. As blazars are distributed across the universe, we can measure the EBL at different epochs.”

The study was able to probe light emitted by stars that existed when the universe was just 0.6 billion years old or so — relatively an infant.

These first stars are thought to have been quite different from stars that form today. In general, they were much more massive, containing up to hundreds of times the mass of our sun, and burned hotter, brighter, and for shorter lifetimes than stars today. [Gallery: History & Structure of the Universe]

This plot shows the locations of 150 blazars (green dots) used in the EBL study. Image released Nov. 1, 2012.

This plot shows the locations of 150 blazars (green dots) used in the EBL study. Image released Nov. 1, 2012.

The new measurements should help astronomers answer some of their most basic questions about the first generations of stars, such as how quickly they formed, and how soon after the birth of the universe the first stars came to be, researchers said.

Already, the scientists have found that the first stars’ peak formation rate must have been lower than previously thought.

Ultimately, the researchers would like to constrain this parameter further, and eventually to glimpse these ancient stars themselves. Future technology, such as NASA’s successor to the Hubble Space Telescope, called the James Webb Space Telescope (expected to come online by 2018), should come closer to doing the job.

“Detecting these stars is very important, but currently impossible,” Ajello said. “The Webb Telescope in a few years might be able to see the first galaxies (not the first stars though). In this way we are already able to set constraints on the amount and role of these stars in the early universe.”

The findings are reported in the Nov. 2 issue of the journal Science.
Source

September 18, 2012

World’s most powerful sky-mapping machine sees 8-billion year-old light

The Blanco telescope in Chile. (T. Abbott and NOAO/AURA/NSF)

The Blanco telescope in Chile. (T. Abbott and NOAO/AURA/NSF)

A new telescope camera in Chile focused on mysterious dark energy has taken its first photos of extremely distant galaxies.

The images represent the first observations — called “first light” — of an instrument called the Dark Energy Camera that was eight years in the works.

“The achievement of first light through the Dark Energy Camera begins a significant new era in our exploration of the cosmic frontier,” James Siegrist, associate director of science for high energy physics at the U.S. Department of Energy, said in a statement. “The results of this survey will bring us closer to understanding the mystery of dark energy, and what it means for the universe.”

This photo from the new Dark Energy Camera, taken in September 2012, shows the barred spiral galaxy NGC 1365, in the Fornax cluster of galaxies, which lies about 60 million light years from Earth. (Dark Energy Survey Collaboration)

This photo from the new Dark Energy Camera, taken in September 2012, shows the barred spiral galaxy NGC 1365, in the Fornax cluster of galaxies, which lies about 60 million light years from Earth. (Dark Energy Survey Collaboration)

Scientists think dark energy makes up 74 percent of the universe, yet they have very little idea what it is. For now, it is the name given to the force that’s counteracting gravity, causing the expansion of the universe to accelerate.

The Dark Energy Camera is designed to study this puzzle by mapping out the distant universe to more accurate pin down its current and past expansion rates.

‘This survey will bring us closer to understanding the mystery of dark energy.’

– James Siegrist, associate director at U.S. Department of Energy

“The Dark Energy Survey will help us understand why the expansion of the universe is accelerating, rather than slowing due to gravity,” said Brenna Flaugher, project manager and scientist at Fermilab. “It is extremely satisfying to see the efforts of all the people involved in this project finally come together.”

The new instrument — a 570-megapixel camera — took its first photos on Sept. 12, taking aim at a portion of the southern sky from atop a mountain in the Chilean Andes. The Dark Energy Camera was built at the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Ill., and was installed on the Victor M. Blanco telescope at the Cerro Tololo Inter-American Observatory, the southern branch of the U.S. National Optical Astronomy Observatory (NOAO).

Each photo by the camera can capture up to 100,000 galaxies as far away as 8 billion light-years.

This zoomed-in image from the Dark Energy Camera of the center of the globular star cluster 47 Tucanae, which lies about 17,000 light years from Earth. (Dark Energy Survey Collaboration)

This zoomed-in image from the Dark Energy Camera of the center of the globular star cluster 47 Tucanae, which lies about 17,000 light years from Earth. (Dark Energy Survey Collaboration)

“We’re very excited to bring the Dark Energy Camera online and make it available for the astronomical community through NOAO’s open access telescope allocation,” said Chris Smith, director of the Cerro-Tololo Inter-American Observatory. “With it, we provide astronomers from all over the world a powerful new tool to explore the outstanding questions of our time, perhaps the most pressing of which is thenature of dark energy.”

In December, after the camera is tested, it will begin the Dark Energy Survey, the largest galaxy survey ever undertaken, by mapping one-eighth of the sky. Researchers estimate the survey should spot 300 million galaxies, 100,000 galaxy clusters and 4,000 exploding stars, called supernovas.

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April 30, 2012

Maybe black holes don’t really exist

Filed under: Big Bang, Cool, Gamma Ray Bursts, Wierd — bferrari @ 5:48 pm
Artist's rendition of a Black Hole

Artist's rendition of a Black Hole

On March 28, 2011, the Swift Burst Alert Telescope detected a gamma-ray event that, in contrast with any previously observed gamma-ray burst, remained bright and highly variable for 48 hours. The gamma-ray emission was accompanied by bright x-ray emission that continued for two weeks. Astrophysicists attributed this event to the tidal disruption of a star by a black hole in the center of a distant galaxy. I would argue, however, that it would have been more accurate to describe this event as the tidal disruption of a star by a compact object. This distinction is important because the black-hole model has serious problems. The March event lends support to a heretical idea: that black holes do not exist.

The brightness of the gamma-ray and x-ray emissions suggests they are coming from a jet of charged particles moving at nearly the speed of light, but there is no obvious reason why the tidal disruption of star by a black hole should give rise to such a jet. In fact, the astrophysical community has been struggling to explain the observed ubiquity of jets. A leading idea is that, in the presence of a external magnetic field, electromagnetic energy is extracted from a rotating black hole and used to accelerate charged particles. The source of the field could be the disk of material swirling around the black hole. Yet disks do not generate magnetic fields with the right shape to produce well-collimated beams of particles.

More deeply, there are fundamental reasons why no compact object can be a black hole. The problem is that solutions of Einstein’s general-relativity equations that contain event horizons are inconsistent with quantum mechanics. For example, these spacetimes do not possess a universal time, which is required for quantum mechanics to make sense. Astrophysicists came to accept the idea of black hole because the gravitational collapse of sufficiently large masses cannot be stopped by ordinary means. But Pawel Mazur and I realized some time ago that quantum gravitational effects modify the collapse process.

Ordinary matter will be converted into vacuum energy when it is compacted to the point where general relativity predicts that an event horizon would begin to form. In contrast with ordinary mass-energy, vacuum energy is gravitationally repulsive, so it would act to stop the collapse and stabilize the object. At the surface of such objects, there is a transition layer between the large vacuum energy of the interior and the very small cosmological vacuum energy. In 2000 my colleagues and I suggested that this transition layer represents a continuous quantum phase transition of the vacuum. In 2003 George Musser wrote in Scientific American about the concept and suggested the name “crystal stars”. But I prefer the name “dark energy stars”.

Low-energy particles entering a dark energy star do not disappear, but follow a curved trajectory and emerge from the surface in much the same way that light does in a defocussing lens. On the other hand, the surface is opaque to elementary particles having energies exceeding a certain threshold. This is a result of the fact that near to a continuous phase transition, there are large fluctuations in the energy density, which in the case of a dark energy star means in the vicinity of the surface. Because the quarks inside protons and neutrons have energies exceeding the threshold for opaqueness, protons and neutrons falling onto the surface of a dark energy star will decay into positrons, electrons, and gamma-rays. In fact, one can make use of quantum chromodynamics (QCD) to predict the energy spectrum of these decay products [4]. The result is that for both the leptons and gamma-rays the spectrum extends up to energies of several MeV. Thus the model predictes that matter falling onto the surface of a dark energy star will result in the production of high-speed electrons and positrons and gamma-rays. The March 28 Swift event is perhaps the clearest evidence to date of this process.

Dark energy stars can readily explain jets. Their angular momentum is carried by spacetime vortices concentrated near the axis of rotation (arXiv.org/abs/gr-qc/0407033). As a result an external magnetic field will be wrapped around this vortex core in a barber-pole pattern. Injecting nucleon decay electrons and positrons into a rotating dark energy star will result in a highly collimated lepton jet. Such a jet has a structure very similar to that seen in the jets emerging from the centers of many distant galaxies. What is unique about the March 28 Swift event is that we can see for the first time that the formation of this kind of jet is completely in accordance with what would be expected in a dark energy star.

We arrive at the following picture. When matter from a nearby star hits the surface of a dark energy star, it is instantaneously converted into gamma-rays, electrons and positrons, the majority of which have energies in the 100 keV to few MeV range. It takes about a minute for these particles to fill the interior of the compact object and form a jet. Because the gamma-rays can scatter off the magnetically guided positrons and electrons, a burst of gamma-rays directed along the axis of rotation will initially accompany the jet. After the supply of gamma-rays is exhausted, a beamed emission of x-rays will persist as long as the supply of electrons and positrons lasts.

I doubt that this event alone will dislodge black holes as the astrophysical community’s standard model for compact objects. On the other hand, the unique properties of the March 28 event, together with other ways that the dark energy star theory might be tested in the near future, such as direct millimeter VLBI observations of the massive compact objects at the center of own and nearby galaxies, may soon allow the astrophysical community to see that black holes are really crystal stars.

About the Author: George Chapline is a theoretical physicist at the Lawrence Livermore National Laboratory. He led the team that demonstrated the first working x-ray laser, developed the concept of a “gossamer metal,” and has contributed to string theory.

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