Update on 13 December 2010: The object is still a puzzle, says co-discoverer Tom Muxlow. "It was still there the last time we looked, so its lifetime is now well over a year," he says. "We are continuing to monitor this object."
There is something strange in the cosmic neighbourhood. An unknown object in the nearby galaxy M82 has started sending out radio waves, and the emission does not look like anything seen anywhere in the universe before.
"We don't know what it is," says co-discoverer Tom Muxlow of Jodrell Bank Centre for Astrophysics near Macclesfield, UK.
The thing appeared in May last year, while Muxlow and his colleagues were monitoring an unrelated stellar explosion in M82 using the MERLIN network of radio telescopes in the UK. A bright spot of radio emission emerged over only a few days, quite rapidly in astronomical terms. Since then it has done very little except baffle astrophysicists.
It certainly does not fit the pattern of radio emissions from supernovae: they usually get brighter over a few weeks and then fade away over months, with the spectrum of the radiation changing all the while. The new source has hardly changed in brightness over the course of a year, and its spectrum is steady.
Why do straight men devote so much headspace to those big, bulbous bags of fat drooping from women's chests? Scientists have never satisfactorily explained men's curious breast fixation, but now, a neuroscientist has struck upon an explanation that he says "just makes a lot of sense."
Larry Young, a professor of psychiatry at Emory University who studies the neurological basis of complex social behaviors, thinks human evolution has harnessed an ancient neural circuit that originally evolved to strengthen the mother-infant bond during breast-feeding, and now uses this brain circuitry to strengthen the bond between couples as well. The result? Men, like babies, love breasts.
When a woman's nipples are stimulated during breast-feeding, the neurochemical oxytocin, otherwise known as the "love drug," floods her brain, helping to focus her attention and affection on her baby. But research over the past few years has shown that in humans, this circuitry isn't reserved for exclusive use by infants.
Recent studies have found that nipple stimulation enhances sexual arousal in the great majority of women, and it activates the same brain areas as vagi-nal and clitoral stimulation. When a sexual partner touches, massages or nibbles a woman's breasts, Young said, this triggers the release of oxytocin in the woman's brain, just like what happens when a baby nurses. But in this context, the oxytocin focuses the woman's attention on her sexual partner, strengthening her desire to bond with this person.
The universe abounds with dark matter. Nobody knows what it consists of. University of Oslo physicists have now come up with a mathematical explanation that could solve the mystery once and for all.
Astrophysicists have known for the last 80 years that most of the universe consists of an unknown, dark matter. The solution to the mystery may now be just around the corner.
"We are looking for a new member of our particle zoo in order to explain dark matter. We know that it is a very exotic beast. And we have found a plausible explanation," reports Are Raklev, an associate professor in particle physics in the University of Oslo's Department of Physics to the research magazine Apollon. He is the university's leading theorist in astroparticle physics and has launched a model that explains what dark matter may consist of and how one can discover the invisible particles experimentally.
Even though dark matter is invisible, astrophysicists know it exists. Without this dark matter it is impossible to explain how the visible things in the universe hang together.
An 80-year fight
The world famous, Swiss physicist Fritz Zwicky was speculating on what dark matter might be as early as the 1930s.
Astrophysicists have calculated that 80 per cent of all the mass in the universe is dark, invisible matter. Thanks to gravity this dark matter clumps together as ordinary matter.
Dark matter can explain why stars move like they do. Dark matter may also explain the rotation speed of galaxies.
"Even though we can calculate how much dark matter there is in the universe, we still know little about what dark matter is. The particles in dark matter must either have a lot of mass, or there must be very many of them. Neutrinos meet all the requirements of dark matter. But there is one big difficulty. They have far too little mass."
Are Raklev is now trying to prove that dark matter consists of gravitinos. This is a particle that has been unfairly treated for years.
And just what are gravitinos? Hold tight: gravitinos are the supersymmetric partner of gravitons.
Or, to be even more precise: "The gravitino is the hypothetical, supersymmetric partner of the hypothetical particle graviton, so it is also impossible to predict a more hypothetical particle than this," laughs Raklev, who writes on his web pages that he is looking for dark material both under his sofa and other places.
In order to dig deeper into why Raklev believes dark matter consists of gravitinos, and have any chance at all of understanding the theory behind gravitinos, Apollon has to take a couple of steps back:
Step 1: Supersymmetry
Physicists want to find out whether or not nature is supersymmetric. Supersymmetry means that there is a symmetry between matter and forces. For each type of electron and quark there is a corresponding heavy, supersymmetric partner. The supersymmetric particles were created in the instant after the Big Bang. If some of them have survived to today, they may be what dark matter is made of.
The supersymmetric partner of the gravitino is, as Apollon said, the graviton.
"A graviton is the particle we believe mediates gravitational force, just like a photon, the light particle, mediates electromagnetic force. While gravitons do not weigh anything at all, gravitinos may weigh a great deal. If nature is supersymmetric and gravitons exist, then gravitinos also exist. And vice versa. This is pure mathematics."
But there is a small but. Physicists cannot demonstrate the relationship between gravitons and gravitinos before they have managed to unify all the forces of nature.
Step 2: The forces of nature
One of the biggest things physicists long to do is to unify all the forces of nature in a single theory. In the middle of the last century physicists discovered that electricity and magnetism were part of the same force of nature. This force has since been called electromagnetism. Two of the other forces of nature are the strong nuclear force and the weak nuclear force. The weak nuclear force can be seen in, among things, radioactivity. The strong nuclear force is ten billion times as strong and binds together neutrons and protons.
In the 1970s, electromagnetism was unified with the strong and weak nuclear forces in what physicists call the standard model.
The fourth force of nature is gravity. Even though it is unbelievably painful to fall down stairs, gravity is the weakest of the four forces of nature.
The problem is that physicists have not yet been able to unify gravity with the three other forces of nature. The day physicists gain a unified understanding of all four forces of nature, they will gain a unique understanding of the world. This will make it possible to describe all imaginable interactions between all possible particles in nature. Physicists call this the ToE Theory (Theory of Everything).
"In order to unify gravitational force with the other three forces of nature we have to understand gravity as quantum theory. This means we need a theory in which the particle graviton is included in the atomic nucleus."
Researchers are now looking for signs of both supersymmetry and the ToE Theory. Discovering the graviton would be an enormous step in this direction.
Reveals dark matter
As the reader may have understood, it is very difficult to research dark matter. This is because dark matter has no electromagnetic relationships to terrestrial particles at all. One example of dark matter is the aforementioned neutrino. Unfortunately, neutrinos make up only an imperceptibly tiny part of dark matter.
Even though it has not been possible to observe dark matter, several billion neutrinos race through your body every second. However, their speed is somewhat limited. The particles move just as slowly as the speed the solar system moves around the galaxy. In other words, a mere 400 kilometres a second.
"When there are no electromagnetic relationships with visible particles, the particles can pass right through us without any measuring instruments detecting them. This is where supersymmetry comes in. If supersymmetry is right, physicists can explain why there is dark matter in the universe. That is what is fun about my job," laughs Raklev.
He is now asserting that dark matter mostly consists of gravitinos.
"Supersymmetry simplifies everything. If the ToE Theory exists, in other words if it is possible to unify the four forces of nature, gravitinos must exist."
The gravitinos were formed right after the Big Bang.
"A short time after the Big Bang we had a soup of particles that collided. Gluons, which are the force bearing particles in the strong nuclear force, collided with other gluons and emitted gravitinos. Many gravitinos were formed after the Big Bang, while the universe was still plasma. So we have an explanation of why gravitinos exist."
Changed life span
Physicists have up to now viewed gravitinos as a problem. They have believed that the theory of supersymmetry does not work because there are too many gravitinos.
"Physicists have therefore strived to eliminate gravitinos from their models. We, on the other hand, have found a new explanation that unifies the supersymmetry model with dark matter that consists of gravitinos. If dark matter is not stable, but just very long lived, it is possible to explain how dark matter consists of gravitinos."
In the old models dark matter was always everlasting. This meant that gravitinos were a bothersome part of the supersymmetry model. In Raklev's new model, their life span is no longer endless. Nonetheless, the average life span of gravitinos is very long and actually longer than the life span of the universe.
However, there is a big difference between an unending life span and a life span of more than 15 billion years. With limited a life span, gravitinos must be converted into other particles. It is precisely this conversion effect that can be measured. And the conversion explains the model.
"We believe that almost all dark matter is gravitinos. The explanation lies in very hard mathematics. We are developing special models that calculate the consequences of these theories and we predict how the particles can be observed in experiments."
The measurements are underway
Researchers are now trying to test this experimentally and explain why these new particles have not yet been seen in the CERN experiments in Geneva in Switzerland.
"On the other hand, it should theoretically possible to observe them from a space probe."
The simplest way of observing gravitinos could be studying what happens if two particles collide out in the universe and are converted into other particles such as photons or antimatter.
Even though the collisions occur very rarely, there is still so much dark matter in the universe that a significant number of photons should be able to be produced.
The big problem is that gravitinos do not collide.
"At least it happens so rarely that we could never hope to observe it."
Nonetheless there is hope
"Luckily for us, gravitinos are not one hundred per cent stable. They are converted into something else at some point. We can predict what the signal looks like after gravitinos have been converted. The conversion will send out a small electromagnetic wave. This is also called a gamma ray."
NASA's Fermi-LAT space probe is currently measuring gamma rays. A number of research groups are now analysing the data.
"So far we have only seen noise. But one of the research groups claim they have observed a small, suspicious surplus of gamma rays from the centre of our galaxy. Their observations may fit our models," says the man behind the very difficult mathematical model for dark matter, associate professor in theoretical particle physics, Are Raklev.
Interesting, I'm no expert but I've always read about gravitons(very limited) in the context of just a convenient, mathematical construct in limited field theory. I don't see how you can "pretend" the graviton is real to apply it to something that doesn't have a fixed flat background like dark matter.
This miniature ecosystem has been thriving in an almost completely isolated state for more than forty years. It has been watered just once in that time.
The original single spiderwort plant has grown and multiplied, putting out seedlings. As it has access to light, it continues to photosynthesize. The water builds up on the inside of the bottle and then rains back down on the plants in a miniature version of the water cycle.
As leaves die, they fall off and rot at the bottom producing the carbon dioxide and nutrients required for more plants to grow.
The first soldier to survive after losing all four limbs in the Iraq war has received a double-arm transplant.
Brendan Marrocco had the operation on Dec. 18 at Johns Hopkins Hospital in Baltimore, his father said Monday. The 26-year-old Marrocco, who is from New York City, was injured by a roadside bomb in 2009.
He also received bone marrow from the same dead donor who supplied his new arms. That novel approach is aimed at helping his body accept the new limbs with minimal medication to prevent rejection.
The military is sponsoring operations like these to help wounded troops. About 300 have lost arms or hands in the wars.
I knew that occasionally there are hand transplants and such. But I didn't know modern medicine did whole arms now. Impressive.