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

Computer model shows moon's core surrounded by liquid - Earth Gravitational pull

A team of researchers with team members from China, the U.S. and Japan has created a computer model that shows that the moon is not solid all the way through, instead, it shows a liquid layer surrounding the core. 

In their paper published in the journal Nature Geoscience, the team suggests the liquid layer, if it's really there, is caused by friction due to Earth's gravity.

Scientists have noted anomalies in measurements of the moon's orbit and associated gravitational readings for some time.

Such anomalies have defied explanation, however, as models built to replicate them have generally produced results that weren't very clear.

The Earth and the Moon, an image taken from Mars by the MRO.

Credit: Nasa

At root however, has been the idea that the moon's core may be covered by a thin layer of liquid.

The team noted that gravitational readings of the moon indicate that there is rotation at the core that is not the same as other rotation measurements near the core. This suggests a liquid outer layer.

To getter a better idea of what might be going on at the moon's center, the researchers built a computer model that takes into account the gravity exerted by the moon, the earth and the sun.

Early Science Fiction Image of Moon

When set into motion, the model showed that a liquid layer over the core gave the same gravity readings as scientists have found when measuring the real moon.

This suggests, the team reports, that a liquid layer does truly exist, and likely has been there for a very long time.

As for why such a layer would exist, the team suggests that the tug of Earth's gravity, tidal heating, is likely playing a role, causing friction between the core and material above it, resulting in the creation and maintenance of a liquid layer.

A lot more research will have to be done, of course, before scientists accept the results of the computer model but if such research should prove that there is a liquid layer, scientists might have to do some rethinking of theories that describe the origin of the moon.

If the moon was created due to a large body striking Earth, why did it not cool down over the four and half billion years since then, to the extent that it would be too cold for a liquid layer to exist today?

More information: Nature Geoscience (2014) DOI: 10.1038/ngeo2211

When Galaxies Collide: Interacting Strongly

The galaxies seen here — NGC 6621, on the right, and NGC 6622, to the left – are seen about 100 million years into their merger.

Gravitational forces have wrapped a long tail of stars around both galaxies as well as triggering an extensive burst of stellar formation.

The pair are located in the constellation Draco, approximately 300 million light-years from Earth.

Image: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and W. Keel (University of Alabama, Tuscaloosa)

When Galaxies Collide: Skater Galaxies

Connected via a long stellar bridge, the two galaxies in UGC 8335 are pulling one another gravitationally with all their might.

The collision is happening 400 million light-years away in the constellation Ursa Major.

Image: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)

NASA Kepler: 'Invisible' planet discovered with new technique

The "invisible" world Kepler-19c, seen in the foreground of this artist's conception, was discovered solely through its gravitational influence on the companion world Kepler-19b — the dot crossing the star's face.

Kepler-19b is slightly more than twice the diameter of Earth, and is probably a "mini-Neptune." Nothing is known about Kepler-19c other than that it exists.

For the first time, scientists have definitively discovered an "invisible" alien planet by noticing how its gravity affects the orbit of a neighbouring world, a new study reports.

NASA's Kepler space telescope detected both alien planets, which are known as Kepler-19b and Kepler-19c.

Kepler spotted 19b as it passed in front of, or transited, its host star. Researchers then inferred the existence of 19c after observing that 19b's transits periodically came a little later or earlier than expected. The gravity of 19c tugs on 19b, changing its orbit.

The discovery of Kepler-19c marks the first time this method — known as transit timing variation, or TTV — has robustly found an exoplanet, researchers said. But it almost certainly won't be the last.

"My expectation is that this method will be applied dozens of times, if not more, for other candidates in the Kepler mission," said study lead author Sarah Ballard of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.

Finding two new planets
The Kepler spacecraft launched in March 2009. It typically hunts for alien worlds by measuring the telltale dips in a star's brightness caused when a planet crosses the star's face from the telescope's perspective, blocking some of its light.

Kepler has been incredibly successful using this so-called transit method, spotting 1,235 candidate alien planets in its first four months of operation. That's the way it detected Kepler-19b, a world 650 light-years away from Earth in the constellation Lyra.

Kepler-19b has a diameter about 2.2 times that of Earth, researchers said, and orbits 8.4 million miles (13.5 million kilometers) from its parent star. The planet likely has a surface temperature around 900 degrees Fahrenheit (482 degrees Celsius).

Kepler-19b transits its host star once every nine days and seven hours. But that number isn't constant, Ballard and her team found; transits can occur up to five minutes early or five minutes late. That variation told them another planet was tugging on 19b, alternately speeding it up and slowing it down.

In our own solar system, scientists used similar methods to predict the existence of the planet Neptune. Astronomers noticed that Uranus did not orbit the sun exactly as expected, and surmised that an unseen planet was pulling on it. This prediction was borne out when telescopes confirmed Neptune's existence in 1846.

Researchers know little about Kepler-19c at the moment. It takes the alien world 160 days or less to zip around its host star, and 19c's mass could range from a few times that of Earth to six times that of Jupiter, researchers said.

But 19c should start coming into clearer focus soon.

"It's a mystery world, but of course we don't expect it to remain a mystery," study co-author David Charbonneau, also of the Harvard-Smithsonian Center for Astrophysics, told Space.com in an email. "Kepler, and large ground-based telescopes, should help us figure out its true identity soon enough!"

The study will be published in The Astrophysical Journal.

ESO Image: Spiral Galaxy Pair Shaped by Gravitational Tug-of-War

A pair of spiral galaxies displays some curious features in a new image from the European Southern Observatory (ESO), showing that the members of the galactic duo are close enough to exert their distorting gravitational influence on each other.

The gravitational tug-of-war has warped the spiral shape of one galaxy, NGC 3169, and fragmented the dust lanes of its companion NGC 3166.

Meanwhile, a third, smaller galaxy to the lower right, NGC 3165, has a front-row seat to the gravitational twisting and pulling of its bigger galactic neighbors.

The image was captured by the Wide Field Imager on the MPG/ESO 2.2-meter telescope at the La Silla Observatory in Chile.

NASA Cassini Double Play: Enceladus And Titan

On the left, Saturn's moon Enceladus is backlit by the sun, showing the fountain-like sources of the fine spray of material that towers over the south polar region.

On the right, is a composite image of Titan. Image credit: NASA/JPL/SSI and NASA/JPL/University of Arizona

About a month and a half after its last double flyby, NASA's Cassini spacecraft will be turning another double play this week, visiting the geyser moon Enceladus and the hazy moon Titan.

The alignment of the moons means that Cassini can catch glimpses of these two contrasting worlds within less than 48 hours, with no detours in between.

Cassini will make its closest approach to Enceladus late at night on May 17 Pacific time, which is in the early hours of May 18 UTC. The spacecraft will pass within about 435 kilometers (270 miles) of the moon's surface.

The main scientific goal at Enceladus will be to watch the sun play peekaboo behind the water-rich plume emanating from the moon's south polar region. Scientists using the ultraviolet imaging spectrograph will be able to use the flickering light to measure whether there is molecular nitrogen in the plume.

Ammonia has already been detected in the plume and scientists know heat can decompose ammonia into nitrogen molecules. Determining the amount of molecular nitrogen in the plume will give scientists clues about thermal processing in the moon's interior.

The second of Cassini's two flybys is an encounter with Titan. The closest approach will take place in the late evening May 19 Pacific time, which is in the early hours of May 20 UTC. The spacecraft will fly to within 1,400 kilometers (750 miles) of the surface.

Cassini will primarily be doing radio science during this pass to detect the subtle variations in the gravitational tug on the spacecraft by Titan, which is 25 percent larger in volume than the planet Mercury.

Analyzing the data will help scientists learn whether Titan has a liquid ocean under its surface and get a better picture of its internal structure. The composite infrared spectrometer will also get its southernmost pass for thermal data to fill out its temperature map of the smoggy moon.

Cassini has made four previous double flybys and one more is planned in the years ahead.

Dents in Earth's gravitational field due to plumes - physics-math

Ancient pieces of continental crust that are falling to the bottom of the Earth's mantle could explain mysterious dents in our planet's gravitational field.

Sail towards the centre of the Indian Ocean and you will find yourself losing weight because the Earth's gravitational field is weaker in this region. Similar dents in field strength are found in the north-east Pacific Ocean and the Ross Sea.

These weaknesses are believed to be created by "slab graveyards" – ancient pieces of crust and sediment that were pushed down into the Earth when plates collided and are now falling through the mantle. The slabs are denser than the surrounding mantle, so they have a stronger gravitational pull. As they fall, however, their effect on the gravitational field at the Earth's surface decreases.

But surrounding these areas are even weaker, unexplained dents in the field. Now Sonja Spasojevic from the California Institute of Technology in Pasadena and colleagues say this could be because the movement of the slabs through the mantle forces plumes of less dense material to rise towards the surface. The distribution of the unexplained weak spots simply reflects the pattern of these plumes, they say.

However, there are other ways the slabs may be creating density changes in the mantle, including chemical reactions that may occur between the slab and the mantle. "The new explanation is plausible but there are other possibilities too," says Norm Sleep a geophysicist at Stanford University in California.

Journal reference: Nature Geoscience, DOI: 10.1038/ngeo855

NASA Shuttle Endeavour docking delay by Earth's gravitational pull

Astronauts aboard space shuttle Endeavour had to wait an uncommonly long time to board the International Space Station. NASA blamed the orbital holdup on no less than the entire planet Earth — actually, its gravitational pull.

Endeavour docked at the space station Wednesday morning at 12:06 a.m. EST (0506 GMT), but it took nearly an hour for the two massive spaceships to form a secure connection using a complicated set of hooks and latches. Normally, the spring-loaded docking rings between the station and a visiting shuttle dampen out the vibrations associated with their rendezvous rather quickly, and align themselves automatically.

But not so during Endeavour's arrival. It took about 45 minutes for the relative motion to damp out. Only then could the docking systems align and pull both spacecraft together.

Space shuttle flight director Kwatsi Alibaruho said the orbital oddity was actually caused by two things: The massive bulk of the joined space station and shuttle, and the constant tug of Earth's gravity.

With Endeavour docked at the International Space Station, the complete "stack" — as NASA calls it — weighs more than 1 million pounds (453,600 kg).

But unlike small round satellites or, say, the moon, the docked space shuttle and station aren't symmetrical, and therein lies the problem, Alibaruho said, because external forces can affect a shuttle docking.