Universe – Page 5 – astroengine.com

No Naked Singularity After Black Hole Collision

Black holes cannot be naked... the event horizon will always be there to cover them up...

You can manipulate a black hole as much as you like but you’ll never get rid of its event horizon, a new study suggests. This may sound a little odd, the event horizon is what makes the black hole, well… black. However, in the centre of a black hole, hidden deep inside the event horizon, is a singularity. A singularity is a mathematical consequence, it is also a point in space where the laws of physics do not apply. Mathematics also predicts that singularities can exist without an associated event horizon, but this means that we’d be able to physically see a black hole’s singularity. This theoretical entity is known as a “naked singularity” and physicists are at a loss to explain what one would look like.

Like any good physics experiment, an international team from the US, Germany, Portugal and Mexico have decided to simulate the most extreme situation possible in the aim of stripping a pair of black holes of their event horizons. They did this by constructing an energetic collision between two black holes travelling close to the speed of light, crashing head-on. Here’s what they discovered…
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The First Visual Evidence of Dark Energy?

A map of the faint microwave radiation left over after the big bang shows superclusters (red circles) and supervoids (blue circles). Credit: B. Granett, M. Neyrinck, I. Szapudi

A new cosmic map has been created by University of Hawaii astronomers showing the fingerprint of dark energy throughout the observable Universe. This is the first time such precise direct evidence of the mysterious force that is believed to be behind the continuing expansion of the Universe. By analysing microwave background radiation (the electromagnetic “echo” left over from the Big Bang), the Hawaii team have looked at the characteristics of the radiation as it passes through supervoids and superclusters. If the theory of dark energy is correct, this cosmic background radiation should cool when passing through superclusters and warm up when passing through supervoids. Analysing a huge amount of data from the Sloan Digital Sky Survey, the researchers have observed what the theory predicts and calculated that there is a 1 in 20,000 chance that their results are random. It therefore seems likely that the effect is caused by the presence of dark energy, giving us the best view yet of this strange energy that appears to permeate through the entire expanding Universe…
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Gravitational Wave Theory Takes Another Kick in the Teeth

Northern leg of the LIGO facility on the Hanford Reservation (LIGO)

Six years and nearly 400 million dollars later, the Laser Interferometer Gravitational-Wave Observatory (LIGO) still hasn’t turned up the evidence for gravitational waves. Gravitational waves are predicted by fundamental Einstein general relativity theories, but we haven’t been able to detect them. Is it because the first generation laser interferometers are not sensitive enough? Is it because LIGO needs more time to see through the cosmic noise to root out the gravitational wave signature? This is a deeply worrying non-development for physicists as a null result means that something isn’t quite right. We are certain (in theory) that these waves should be rippling through space-time (after all, massive objects are colliding and exploding all the time throughout the Universe), but if we can’t detect the things in our own cosmic back yard, something must be awry. In a recent publication, LIGO scientists have discussed the lack of evidence for gravitational waves, but remain upbeat that they can still be found…
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New Exotic Particle May Explain Milky Way Gamma-Ray Phenomenon

Chandra observation of Cassiopeia A, a young supernova remnant in our galaxy - a prominent source of high-energy particles (NASA/CXC/MIT/UMass Amherst/M. D. Stage et al.) — Chandra observation of Cassiopeia A, a young supernova remnant in our galaxy - a prominant source of high-energy particles (NASA/CXC/MIT/UMass Amherst/M. D. Stage et al.)

There is something strange happening in the core of the Milky Way. A space observatory measuring the energy and distribution of gamma-rays in the cosmos has made an unexpected (and perplexing) discovery. It would seem there is a very high proportion of gamma-ray photons emanating from our galactic core with a very distinctive signature; they have a precise energy of 511 keV (8×10^-14 Joules), and there’s a lot of them. So what could possibly be producing these 511 keV gamma-rays? It turns out, 511 keV is a magic number; it is the exact rest mass energy of a positron (the antimatter particle of the electron). So this is fairly conclusive evidence that positrons are dying (i.e. annihilating) in vast numbers in our galactic nuclei. Still, this is of little help to astrophysicists as there is no known mechanism for producing such high numbers of annihilating positrons. Ideas have been put forward, but there’s a new possibility, involving some new particle physics and some lateral thinking…
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Recoiling Supermassive Black Holes and Stellar Flares

Astrophysicists love to simulate huge collisions, and they don’t get much bigger than this. From the discoverers of the first ever observed black hole collision back in April, new observational characteristics have been researched and Max Planck astrophysicists believe that after two supermassive black holes (SMBHs) have collided, they recoil and drag flaring stars with them. By looking out for anomalous X-ray flares in intergalactic space, or off-galactic nuclei locations, repelled black holes may be spotted powering their way into deep space at velocities of up to 4000 kms^-1…
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Is the Sun a Dark Matter Factory?

The hypothetical axion is a particle that might help scientists work out where the bulk of dark matter may be held in the Universe. So far, there has been much talk about the search for another type of hypothetical particle, the weakly interacting massive particle (WIMP), and little attention has been paid to the lowly axion. WIMPs are very appealing to scientists as proving they exist will help patch some holes in quantum theory. What’s more, WIMP detectors need to be huge, large volumes of underground caverns filled with hi-tech sensors and cleaning fluid – this makes for a cool funding proposal; think up and grand idea, explain that it will prove our understanding of the Universe and then receive a multi-billion $/£/€ cheque (it’s not quite as easy as that, but there are socioeconomic and political reasons for building such an awesome structure).

So how do you go about finding an axion? Surely this exotic particle will need an even bigger detector, especially as it has zero charge, very low mass and cannot interact via the strong and weak nuclear forces? Actually, a large WIMP-type detector would be useless for axion detection. Fortunately axions have a neat interaction with magnetic fields that can be detected with existing instrumentation. What produces the strongest magnetic field in the Solar System? This is where the Sun can help out…
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The Case of the Supermassive Black Hole, the Infrared Object and Perceived Accuracy of Science

There is a trend in astronomical observations to label strange and exotic objects with superlative names. Take “supermassive” black holes for instance. Yes they are more massive than intermediate black holes, bigger than stellar black holes, and in a whole different league to theoretical micro-black holes. But is the label “supermassive” an accurate description? Is it even scientific?

After reading a very interesting article written by Michael Gmirkin on “Incorrect Assumptions in Astrophysics“, I began to relate his investigation into the use of terms to describe astronomical phenomena with very expressive names. Terms like “super-massive”, “ultra-luminous”, and “beyond-bright” are mentioned by Gmirkin, perhaps leading astronomers to incorrect conclusions. Whilst this may be perceived as an issue amongst scientists, what if the media or non-specialist individuals misinterpret the meaning of these grand statements? Could it lead to public misunderstanding of the science, possibly even causing worry when a scientist describes a particle accelerator collision as “recreating the conditions of the Big Bang”?
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The Crab Pulsar is Probed By LIGO. Is it Really a Smooth Neutron Star?

Scientists working with the Laser Interferometer Gravitational-Wave Observatory (LIGO) have announced their first land-mark discovery. LIGO was built to detect gravitational waves (as predicted by Einstein’s general relativity), but this discovery is actually about not detecting gravitational waves. Hold on, what’s all the fuss about then? This sounds like a null result, and in some ways it is. But on the other hand it may be one of the most important neutron star observations ever. So what has LIGO (not) seen?
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What Happens When Two Galaxies Collide?

So what does happen? Will the stars crash into one another, sending out huge emissions of gamma radiation and gravitational waves? The effects of two galaxies meeting and colliding are actually a little more elegant than that – for starters, it’s most likely that none of the stars will meet due to the huge distances between star systems. Also, the merging of the systems will spark a huge campaign of star creation within the newly formed fertile gas clouds. So what will we see long after the galaxies have ripped each other apart? Simulations show huge arcs of tidally-formed dust and stars, looking strangely like the precursors to the galactic ghosts recently observed…
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The Sinister Side of the Cosmos: Killer Galaxies, Cosmic Forensic Science and Deadly Radiation

It’s been a busy day with a range of topics posted on the Universe Today, but all have a common thread: the universe is a deadly place for man and galaxy. For starters, research into the radiation mankind will face when settling on Mars and the Moon could prove to be one of our main challenges in space. The threat of a massive dose of radiation from a solar flare is bad enough, but the gradual damage to our cells and increased risk of cancer is a problem we need to solve, or at least manage. But that’s nothing compared with what dwarf galaxies have to put up with; their larger spiral cousins like to eat them for dinner, leaving behind galactic ghosts of the dwarfs that were…
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