Tag Archives: black holes

Brightest explosion ever seen in the universe

Brightest explosion ever seen in the universe

By Denise Chow

Published November 22, 2013

  • brightest-gamma-ray-burst

    An unusually bright gamma-ray burst produced a jet that emerged at nearly the speed of light. (NASA/SWIFT/CRUZ DEWILDE)

  • gamma-ray-burst-swift-nasa

    A gamma-ray burst that exploded in April 2013 is the most luminous object in the field, as seen in this image from NASA’s Swift satellite. All the other objects seen in the image are stars from our own galaxy, while the gamma-ray burst is milli (NASA/SWIFT SATELLITE)

  • gamma-ray-burst-swift

    Close-up image of the brightest gamma-ray burst ever seen, taken in April 2013 by the ultraviolet/optical telescope on NASA’s Swift satellite. (NASA/SWIFT SATELLITE)

A mysterious blast of light spotted earlier this year near the constellation Leo was actually the brightest gamma-ray burst ever recorded, and was triggered by an extremely powerful stellar explosion, new research reports.

On April 27, several satellites — including NASA’s Swift satellite and Fermi Gamma-ray Space Telescope — observed an unusually bright burst of gamma radiation. The explosion unleashed an energetic jet of particles that traveled at nearly the speed of light, researchers said.

“We suddenly saw a gamma-ray burst that was extremely bright — a monster gamma-ray burst,” study co-author Daniele Malesani, an astrophysicist at the Niels Bohr Institute at the University of Copenhagen in Denmark, said in a statement. “This [was] one of the most powerful gamma-ray bursts we have ever observed with the Swift satellite.” [Top 10 Strangest Things in Space]

The gamma-ray burst was described in a series of studies published online Thursday in the journal Science.

‘The exploding matter was traveling at [nearly] the speed of light.’

– Giacomo Vianello, a postdoctoral scholar at Stanford University

Gamma-ray bursts, or GRBs, are the most powerful type of explosions in the universe and typically mark the destruction of a massive star. The original stars are too faint to be seen, but the supernova explosions that signal a star’s death throes can cause violent bursts of gamma radiation, researchers said.

Gamma-ray bursts are usually short but extremely bright. Still, ground-based telescopes have a tough time observing them because Earth’s atmosphere absorbs the gamma radiation.

The extremely bright gamma-ray burst seen earlier this year, officially dubbed GRB 130472A, occurred in a galaxy 3.6 billion light-years away from Earth, which, though still far away, is less than half the distance at which gamma-ray bursts have previously been seen. This closer proximity to Earth enabled astronomers to confirm for the first time that one object can simultaneously create a powerful GRB and a supernova explosion.

“We normally detect GRBs at great distance, meaning they usually appear quite faint,” study co-author Paul O’Brien, an astronomer at the University of Leicester in the United Kingdom, said in a statement. “In this case, the burst happened only a quarter of the way across the universe — meaning it was very bright. On this occasion, a powerful supernova was also produced — something we have not recorded before alongside a powerful GRB — and we will now be seeking to understand this occurrence.”

The jet produced by the gamma-ray burst was formed when a massive star collapsed on itself and created a black hole at its center. This generated a blast wave that caused the stellar remnants to expand, producing a glowing shell of debris that was observed as an extremely bright supernova explosion.

After analyzing properties of the light produced by the gamma-ray burst, scientists determined that the original star was only three to four times the size of the sun, but was 20 to 30 times more massive. This extremely compact star was also rapidly rotating, the researchers said.

The GRB was the brightest and most energetic ever witnessed and triggered dynamic internal and external shock waves that are still not well understood. Though scientists have a clearer view of the violent explosion, mysteries remain. For instance, space telescopes detected more photons and more high-energy gamma-rays than theoretical models predicted for a gamma-ray burst of this magnitude.

Researchers are still investigating why the energy levels seen with GRB 130472A do not quite match predictions from existing models of gamma-ray bursts. Their results could lead to more refined theories about how particles are accelerated, which could help astronomers better predict the behavior of cosmic events.

“The really cool thing about this GRB is that because the exploding matter was traveling at [nearly] the speed of light, we were able to observe relativistic shocks,” study co-author Giacomo Vianello, a postdoctoral scholar at Stanford University in California, said in a statement. “We cannot make a relativistic shock in the lab, so we really don’t know what happens in it, and this is one of the main unknown assumptions in the model. These observations challenge the models and can lead us to a better understanding of physics.”

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Space-time loops may explain black holes

Space-time loops may explain black holes

Black holes can't fully be described by general relativity, but physicists hope to understand the inner workings of these strange objects by applying a theory called loop quantum gravity.

Black holes can’t fully be described by general relativity, but physicists hope to understand the inner workings of these strange objects by applying a theory called loop quantum gravity. / FELIPE ESQUIVEL REED

Physics cannot describe what happens inside a black hole. There, current theories break down, and general relativity collides with quantum mechanics, creating what’s called a singularity, or a point at which the equations spit out infinities.

But some advanced physics theories are trying to bridge the gap between general relativity and quantum mechanics, tounderstand what’s truly going on inside the densest objects in the universe. Recently, scientists applied a theory called loop quantum gravity to the case of black holes, and found that inside these objects, space and time may be extremely curved, but that gravity there is not infinite, as general relativity predicts.

This was the first time scientists have applied the full loop quantum gravity theory to black holes, and the results were encouraging, researchers said.

“What they have done is a major step, because they have been able to provide a much more complete description of what really happens near the black hole singularity using loop quantum gravity,” said Abhay Ashtekar, a physicist who studies loop quantum gravity at Pennsylvania State University, who was not involved in the new research.”We still don’t have a clear picture of the details of what happens. So it is opening a new door that other people will follow.” [Images: Black Holes of the Universe]

A black hole is created when a huge star runs out of fuel for nuclear fusion and collapses under its own gravity. The star’s outer layers are expelled, and its core falls in on itself, with the pull of gravity becoming ever stronger, until what’s left is the core’s mass condensed into an extremely small area. According to general relativity, this area is a single point of space-time, and the density there is infinitely large — a singularity.

But most scientists think singularities don’t really exist, that they’re just a sign that equations have broken down and fail to adequately describe reality. Loop quantum gravity appears to be an improvement on general relativity in describing black holes because it doesn’t produce a singularity.

The idea is based on the notion of “quantization,” which breaks an entity up into discrete pieces.Whilequantum mechanics says atoms exist in quantized, discrete states, loop quantum gravity posits that space-time itself is made of quantized, discrete bits, in the form of tiny, one-dimensional loops.

“The loop means the fundamental excitations of space-time themselves are one-dimensional in nature,” said Jorge Pullin, a physicist at Louisiana State University, who co-authored the new study with Rodolfo Gambini of the University of the Republic in Montevideo, Uruguay. “The fundamental building block is a loop, or network of loops. For a visual image, think of a mesh fabric.”

This way of portraying space-time changes fundamental physics, especially in extreme settingssuch as black holes or the Big Bang — which is thought to have birthed the universe. The Big Bang, like black holes, is indescribable under general relativity, understood only as a singularity.

“The subject really took off in 2005 when it was realized loop quantum gravity can naturally resolve the Big Bang singularity and that quantum space-time is much larger than what Einstein envisioned,” Ashtekar told SPACE.com.

Pullin and Gambini said their work is just a preliminary step, far from a full description of the true complexity of black holes.

“This model we’ve done is extremely simple,” Pullin said. Under their simplified model,”the black hole exists forever and doesn’t evolve. As a consequence I cannot tell you exactly what nature is going to do inside a black hole. It could be that the singularity gets replaced by a region that gets highly curved, but not infinitely curved. Or it could be that it just doesn’t make sense — you get a region which doesn’t behave like classical space-time. It would interact with particles in different ways than we normally think.”

Now that they’ve achieved this step, the researchers hope to advance their work by making the black holes in their model more dynamic and changeable.

“The black holes we studied were in empty space — there was no matter in them. They were pure space-time,” Pullin said.”We’re trying to add matter, because then it addsdynamics. We’re in the middle of that now.”

The study was published May 23 in the journal Physical Review Letters.

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Largest Structure in the Universe

Largest Structure In Universe, Large Quasar Group, Challenges Cosmological Principle

Large Quasar Group

Large Quasar Group

Posted: 01/11/2013 9:45 am EST  |  Updated: 01/12/2013 5:34 pm EST

By: Mike Wall

Published: 01/11/2013 04:34 AM EST on SPACE.com

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.”

Large Quasar Group

Large Quasar Group

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 today (Jan. 11) in the Monthly Notices of the Royal Astronomical Society.

Follow SPACE.com senior writer Mike Wall on Twitter @michaeldwall or SPACE.com @Spacedotcom. We’re also on Facebook and Google+

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Dark Matter

This is republished from my Science Column in ConNotations Newszine, where I am a staff writer.  I also write book and movie reviews and other non-fiction for the magazine.  My science column is directed at convention fanboys and fangirls that were not self-punishing enough to get three science degrees like myself, but want to be able to understand complicated topics, like dark matter, string theory, teleportation, where the universe came from, astro-physics, the God Particle, and other issues.  My attempt with each short column is to explain a concept in layman’s terms.  This is on Dark Matter.  The photos were added for this web edition.

Is Space Empty or Full? 

by Michael Bradley

 Most have heard the term “dark matter” but what does it mean?  We look up at the night sky and we notice the stars, constellations, galaxies and heavenly bodies.  Unconsciously, we might also notice everything else – the black portion.  It is human nature to assume that the black portion represents nothingness, and emptiness broken up in its expanse only by those objects we can see.  For the known history of mankind, everyone would have accepted that as truth, until less than one hundred years ago.

As humans, we know and experience our reality through senses; smell, touch, sight, hearing, temperature, etc.  If we cannot sense something, it is often overlooked or missed by our minds.  In physics and astronomy the same is true.  We “see” the sky at night through two major lenses, one is the light emitted by heavenly bodies, and the second is the radiation and radio wave emissions from the sky.  We can observe the lights and the radiations and draw theories to understand them.

Based on the movement of the lights, we learned through observation that the planets rotate, that the Earth moves around the Sun, that we are in a galaxy called the Milky Way, that their are other galaxies, and many helpful facts.  The universe appears to be expanding, which also leads to the Big Bang Theory, calculations of time and so forth.

In the 1880s, Christian Doppler discovered the Doppler Effect, in which sound and light waves are compressed to different frequencies by the motion of mass.  For instance, a rushing locomotive sounds different as its mass moves toward and away from the listener.  This also creates the Blue/Red shift in light from celestial bodies.  As a galaxy spins, the section moving toward us turns bluer, while the section moving away turns redder on the light frequency spectrum.

Using the blue/red shift and physics, scientists were able to calculate the relative mass of galaxies and other objects which spin and cast off light.  Fritz Zwicky noticed in 1934 that the math did not add up, and came up with an explanation now known commonly as “dark matter.”  His theory is that either the majority of the mass of these objects does not give off light, or, the theory of gravitational pull is flawed in its calculations of mass.  To explain this missing mass, he theorized that there must be matter which neither reflects nor gives off light or radiation emissions measurable on Earth, but which has mass.  By only making calculations of spin based on visible matter, we are missing the dark matter.

If the dark matter theory is true, then 83% of the matter in the universe and 23% of the mass energy could be from dark matter.  It could be that our ability to perceive what space is composed of is much like a blind-folded man with ear muffs and a cold trying to describe his surroundings.  Or, consider a dark field and across from you are 1,000 people holding flashlights, but only 230 have them on.  So you think there are only 230 people.

Could there actually be so much out there that we can not see through light or through radiation?

Theorists have explored the possibilities for the last eighty years and have mainly created more theories than answers.  Some say the gravitational theory is wrong and that instead of trying to “fix” the math by the creation of a theoretical dark matter you should start there.  Some have broken up dark matter into deeper theoretical categories, such as Machos and Wimps.  You can’t make this stuff up.

Machos are Massive Astrophysical Compact Halo Objects more commonly referred to as brown dwarfs and black holes, or referred to as baryonic, or more normal matter, that happens to be dark.  Wimps are Weakly Interacting Massive Particles which would be non-baryonic in nature.  Wimps are thought to pass through normal matter though they have mass, without interacting with it.  There are also theories of the dark matter in which they break them into mixed dark matter, cold dark matter, warm dark matter and hot dark matter.  Who says physicists don’t have a sense of humor?

In any case, the next time you look up at the night sky, just realize that mathematically, either all we know about gravity is wrong, or you are seeing only a tiny portion of what is there.  It is 2012, and we often think we have it all figured out, and yet in the very night sky above our heads we understand and perceive very little.



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