Researcher shows that black holes do not exist

This artist's concept depicts a supermassive black hole at the center of a galaxy. 

The blue colour here represents radiation pouring out from material very close to the black hole. 

The grayish structure surrounding the black hole, called a torus, is made up of gas and dust. 

Credit: NASA/JPL-Caltech

Black holes have long captured the public imagination and been the subject of popular culture, from Star Trek to Hollywood.

They are the ultimate unknown, the blackest and most dense objects in the universe that do not even let light escape, and as if they weren't bizarre enough to begin with, now add this to the mix: they don't exist.

By merging two seemingly conflicting theories, Laura Mersini-Houghton, a physics professor at UNC-Chapel Hill in the College of Arts and Sciences, has proven, mathematically, that black holes can never come into being in the first place.

The work not only forces scientists to reimagine the fabric of space-time, but also rethink the origins of the universe.

"I'm still not over the shock," said Mersini-Houghton. "We've been studying this problem for a more than 50 years and this solution gives us a lot to think about."

For decades, black holes were thought to form when a massive star collapses under its own gravity to a single point in space, imagine the Earth being squished into a ball the size of a peanut, called a singularity.

So the story went, an invisible membrane known as the event horizon surrounds the singularity and crossing this horizon means that you could never cross back.

It's the point where a black hole's gravitational pull is so strong that nothing can escape it.

The reason black holes are so bizarre is that it pits two fundamental theories of the universe against each other.

Einstein's theory of gravity predicts the formation of black holes but a fundamental law of quantum theory states that no information from the universe can ever disappear.

Efforts to combine these two theories lead to mathematical nonsense, and became known as the information loss paradox.

In 1974, Stephen Hawking used quantum mechanics to show that black holes emit radiation.

Since then, scientists have detected fingerprints in the cosmos that are consistent with this radiation, identifying an ever-increasing list of the universe's black holes.

But now Mersini-Houghton describes an entirely new scenario. She and Hawking both agree that as a star collapses under its own gravity, it produces Hawking radiation.

However, in her new work, Mersini-Houghton shows that by giving off this radiation, the star also sheds mass. So much so that as it shrinks it no longer has the density to become a black hole.

Before a black hole can form, the dying star swells one last time and then explodes. A singularity never forms and neither does an event horizon.

The take home message of her work is clear: there is no such thing as a black hole.

The paper, which was recently submitted to ArXiv, an online repository of physics papers that is not peer-reviewed, offers exact numerical solutions to this problem and was done in collaboration with Harald Peiffer, an expert on numerical relativity at the University of Toronto.

An earlier paper, by Mersini-Houghton, originally submitted to ArXiv in June, was published in the journal Physics Letters B, and offers approximate solutions to the problem.

Experimental evidence may one day provide physical proof as to whether or not black holes exist in the universe, but for now, Mersini-Houghton says the mathematics are conclusive.

Many physicists and astronomers believe that our universe originated from a singularity that began expanding with the Big Bang.

However, if singularities do not exist, then physicists have to rethink their ideas of the Big Bang and whether it ever happened.

"Physicists have been trying to merge these two theories, Einstein's theory of gravity and quantum mechanics, for decades, but this scenario brings these two theories together, into harmony," said Mersini-Houghton. "And that's a big deal."

More information: Mersini-Houghton's ArXiv papers: Approximate solutions: arxiv.org/abs/arXiv:1406.1525 Exact solutions: arxiv.org/abs/arXiv:1409.1837

Shredded Star Heralds a New Era for Testing Relativity

This illustration highlights the principal features of Swift J1644+57 and summarizes what astronomers have discovered about it. Credit: NASA's Goddard Space Flight Center.

Last year, astronomers discovered a quiescent black hole in a distant galaxy that erupted after shredding and consuming a passing star. Now researchers have identified a distinctive X-ray signal observed in the days following the outburst that comes from matter on the verge of falling into the black hole.

This tell-tale signal, called a quasi-periodic oscillation or QPO, is a characteristic feature of the accretion disks that often surround the most compact objects in the universe - white dwarf stars, neutron stars and black holes.

QPOs have been seen in many stellar-mass black holes, and there is tantalizing evidence for them in a few black holes that may have middleweight masses between 100 and 100,000 times the sun's.

Until the new finding, QPOs had been detected around only one supermassive black hole - the type containing millions of solar masses and located at the centers of galaxies. That object is the Seyfert-type galaxy REJ 1034+396, which at a distance of 576 million light-years lies relatively nearby.

"This discovery extends our reach to the innermost edge of a black hole located billions of light-years away, which is really amazing.

"This gives us an opportunity to explore the nature of black holes and test Einstein's relativity at a time when the universe was very different than it is today," said Rubens Reis, an Einstein Postdoctoral Fellow at the University of Michigan in Ann Arbor.

Reis led the team that uncovered the QPO signal using data from the orbiting Suzaku and XMM-Newton X-ray telescopes, a finding described in a paper published today in Science Express.

The X-ray source known as Swift J1644+57 - after its astronomical coordinates in the constellation Draco - was discovered on March 28, 2011, by NASA's Swift satellite. It was originally assumed to be a more common type of outburst called a gamma-ray burst, but its gradual fade-out matched nothing that had been seen before.

Astronomers soon converged on the idea that what they were seeing was the aftermath of a truly extraordinary event - the awakening of a distant galaxy's dormant black hole as it shredded and gobbled up a passing star. The galaxy is so far away that light from the event had to travel 3.9 billion years before reaching Earth.

The star experienced intense tides as it reached its closest point to the black hole and was quickly torn apart. Some of its gas fell toward the black hole and formed a disk around it.

The innermost part of this disk was rapidly heated to temperatures of millions of degrees, hot enough to emit X-rays. At the same time, through processes still not fully understood, oppositely directed jets perpendicular to the disk formed near the black hole.

These jets blasted matter outward at velocities greater than 90 percent the speed of light along the black hole's spin axis. One of these jets just happened to point straight at Earth.

Nine days after the outburst, Reis, Strohmayer and their colleagues observed Swift J1644+57 using Suzaku, an X-ray satellite operated by the Japan Aerospace Exploration Agency with NASA participation. About ten days later, they then began a longer monitoring campaign using the European Space Agency's XMM-Newton observatory.

"Because matter in the jet was moving so fast and was angled nearly into our line of sight, the effects of relativity boosted its X-ray signal enough that we could catch the QPO, which otherwise would be difficult to detect at so great a distance," said Tod Strohmayer, an astrophysicist and co-author of the study at NASA's Goddard Space Flight Center in Greenbelt, Md.

As hot gas in the innermost disk spirals toward a black hole, it reaches a point astronomers refer to as the innermost stable circular orbit (ISCO). Any closer to the black hole and gas rapidly plunges into the event horizon, the point of no return.

The inward spiraling gas tends to pile up around the ISCO, where it becomes tremendously heated and radiates a flood of X-rays. The brightness of these X-rays varies in a pattern that repeats at a nearly regular interval, creating the QPO signal.

The data show that Swift J1644+57's QPO cycled every 3.5 minutes, which places its source region between 2.2 and 5.8 million miles (4 to 9.3 million km) from the center of the black hole, the exact distance depending on how fast the black hole is rotating.

To put this in perspective, the maximum distance is only about 6 times the diameter of our sun. The distance from the QPO region to the event horizon also depends on rotation speed, but for a black hole spinning at the maximum rate theory allows, the horizon is just inside the ISCO.

"QPOs send us information from the very brim of the black hole, which is where the effects of relativity become most extreme," Reis said. "The ability to gain insight into these processes over such a vast distance is a truly beautiful result and holds great promise."

Atomic Fountain reveals 'Gravitational Red Shift'

Atomic fountain reveals 'gravitational red shift' - New Scientist

YOUR watch runs a tiny bit faster at the top of Everest, where Earth's gravity is slightly weaker, than it does at sea level.

This difference is dubbed the "gravitational red shift" (GRS) and is one of the trickiest predictions of general relativity to measure because the effect is so small.

Now the accuracy of measurement has been improved by a factor of 10,000. Holger Müller at the University of California, Berkeley, decided to reanalyse a decade-old experiment.

In the 1990s, a team led by Nobel laureate Steven Chu made an "atomic fountain" of caesium atoms, launching them 30 centimetres into the air.

A pulse of laser light struck the atoms as they neared their zenith, which kicked them into a two-state quantum superposition. One of the states was given extra momentum, causing it to rise to a slightly higher altitude than the other state before falling.

Müller realised the atoms and their very rapid oscillations could be treated as tiny "clocks" and so could be used to measure GRS. The team compared the difference between the two states and discovered that the state that climbed slightly higher had oscillated ever-so-slightly faster than the lower state.

With an accuracy of 7 parts in a billion, this measurement is 10,000 times as accurate as the previous one (Nature, DOI: 10.1038/nature08776).

Chinese Scientists Seek Support For Dark Matter Mission In Space

Chinese Scientists Seek Support For Dark Matter Mission In Space

Chinese scientists are lobbying for greater government support for a groundbreaking project that would see the launch of a satellite to investigate mysterious dark matter in space.

The Center for Space Science and Applied Research (CSSAR) of the Chinese Academy of Sciences was focusing on developing China's first astronomical satellite to prove the existence of dark matter.

"This would be a major breakthrough in the field of basic science which has been dormant for decades since Einstein's Theory of Relativity," said center director Wu Ji.

Dark matter and dark energy represent the vast majority of the mass in the observable universe, but their presence is only inferred from their gravitational effects on visible matter. Dark matter is believed to play a central role in galaxy evolution and the formation of universe.

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