New picture of the night sky, thanks to Fermi.

Imagine a world shadowed each night by a giant cloud of mysterious, illuminated fog. From far outside our galaxy, one would observe the fog rising 25,000 light years above and below the plane of the Milky Way in two enormous plumes. In fact, this world is our own. Of course, you might be more inclined to believe me if you had the ability to see gamma rays.


The Milky Way, in visible light. Gamma rays are invisible to human eyes.
Image courtesy of erikaj121893.
The new discovery comes from a team of Harvard University scientists working with Fermi's Large Area Telescope (LAT). "This work presents a multiwavelength study of the inner Galaxy and identifies several large-scale gamma-ray features, most notably 2 large structures that we refer to as the 'Fermi bubbles'," wrote the team of astronomers in their recent paper. These Fermi bubbles could be millions of years old, but their origin is something of a mystery. Some have suggested that an ancient boom of star births may have later led to a clustered grouping of star deaths. A large number of supernovae occurring all at once could have injected enough energy into interstellar space to create the two plumes of gamma-ray emitting gas. Others, including Douglas Finkbeiner, a senior member of the team, believe that the massive black hole at the center of our galaxy gave rise to the bubbles. Many galaxies emit jets of high-energy radiation due to infalling material around a central black hole, and the Milky Way may be no exception.


The Fermi bubble structures. Image courtesy of Su et al..
It may seem odd that no one had detected these colossal structures before now. As it turns out, the Milky Way has a separate, amorphous halo of gamma-ray fog that prevented astronomers from observing the bubbles until recently. The bubbles, which are slightly more energetic than the ambient haze and have clearly-defined x-ray edges, were only apparent after subtracting this fog from LAT observations. Fermi continues to observe the universe at gamma-ray frequencies.

Talking weak sauce at the NASW luncheon.

It was almost like kindergarden. One by one, decked out with our nametags and matching knapsacks, each of us chose a boxed lunch and filed into the classroom. There we sat, in a circle, waiting for the woman whose job it was that day to teach us something new. But when Dr. Bonnie Fleming of Yale University arrived, it wasn't a group of five year olds that she stood before; instead, it was a small group of science journalists from around the country, all gathered there to eat, relax, and listen to the latest news in neutrino physics.

"Neutrino physics is a field with many great stories," Fleming began. She then went on to explain that one of the most well-known of these stories is that of flavor oscillation. As it turns out, neutrinos have a sort of quantum mechanical ADD. Rather than sticking with one identity, neutrinos tend to change states spontaneously over the course of their travels. An electron neutrino may suddenly become a tau neutrino, and then a muon neutrino, and then a tau neutrino once more long before you or I have had the chance to ask, "what the- ?"

Regardless of flavor, however, all neutrinos have been said to interact via the same fundamental force: the weak force. As we sat dutifully munching on our sandwiches, Dr. Fleming invited each of us to lay one of our palms on the table and count to three. During that short time, she explained, over a trillion neutrinos had passed through every one of our outstretched hands. Indeed, a neutrino could pass straight through 200 Earths before having any appreciative chance of hitting anything. Physicists call it the "weak" force for a reason.

However, new research at Fermilab has suggested that there may be a fourth, even lazier type of neutrino - one that, unlike its electron, muon and tau counterparts, interacts via the gravitational force rather than the weak force. Perhaps surprisingly, gravity is actually the weakest of the four fundamental forces. If you're not convinced, just rub a balloon against your hair, stick it to the wall, and rest easily in the knowledge that you have just overcome the gravitational influence of the entire planet. Gravity's unbelievable frailty would make directly detecting the alleged new flavor of neutrino, dubbed the sterile neutrino, one of the most daunting tasks yet undertaken by the particle physics community. As it is, neutrinos are notoriously difficult to pin down. "We can only detect their flavor by whatever charged lepton they turn into," said Fleming.

As if neutrinos weren't hard enough to wrap your head around. Rather than exhaust myself by asking any more questions, I just sat there, ate my cookie, and let Dr. Fleming do rest of the talking.

Never-before-seen galaxy clusters make shadowy debut.

You can run, but you can't hide from the Atacama Cosmology Telescope... especially if you're a massive galaxy cluster. Located high in the mountains of Chile, this telescope takes measurements of the CMB, the radiation that has filled the entire universe since the time of the big bang. Earlier this year, the Plank telescope mapped the CMB with unprecedented accuracy. Now, the ACT is providing astronomers with a way of using this radiation to discover galaxy clusters long before observing them visually.


The Atacama Cosmology Telescope, located in the Andes Mountains or northern Chile.
Image courtesy of Till Niermann.
About 300,000 years after the big bang, the universe had cooled and expanded to such an extent that photons could finally travel freely across long stretches of space without being absorbed by atoms. The background radiation that astronomers observe today is made up of those same primordial photons, whose wavelengths have been stretched by the expanding universe. The CMB now reveals itself as a faint 2.7K glow in the microwave range of the electromagnetic spectrum. Small anisotropies in the CMB sky denote regions of the universe that are either slightly more dense or slightly less dense than average.


WMAP provided one of the first maps of the CMB sky.
Image courtesy of NASA.
Thanks to the Atacama Cosmology Telescope, a team of astronomers from Rutgers University was able to predict the locations of several massive galaxy clusters from these anisotropies in the CMB. "The hot gases within the galaxy clusters cause a tiny fraction of the cosmic background radiation to shift to higher energies, which then makes them appear as shadows in one of ACT's observing bands," explained Jack Hughes, a senior member of the team. This phenomenon, called the Sunyaev-Zel'dovich (S-Z) effect, was predicted back in the 1970s, and has been experimentally verified a number of times since its conception. Astronomers hope that the unparalleled sensitivity of the ACT will provide them with more extensive results than ever before. In the game of galaxy detection, new technologies like the ACT are changing all the rules.