With all the press being given to the Large Hadron Collider under construction at CERN, it's interesting to see that the black hole believed to exist at the Milky Way's center -- the object called Sagittarius A* -- seems to be going it one better. The LHC will be able to accelerate protons to seven trillion electronvolts. But Sgr A* evidently slings nearby particles even more energetically, reaching the 100 trillion electrovolt level. Not bad for an object considered to be relatively inactive compared to black holes in other galaxies, and one explanation for the hugely energetic gamma rays streaming from that part of our galaxy. The study in question, reported in Astrophysical Journal Letters, sees the black hole as a cosmic particle accelerator, a region where powerful magnetic fields push particles to extraordinary energies. At play is the interstellar gas extending roughly ten light years from the black hole. Fuvio Melia (University of Arizona) calls Sgr A* "...one of the most...

If dark energy is pushing the universe apart at an accelerating clip, when did its effects begin to be felt? One way to study that question is through the Cosmic Microwave Background, whose infinitesimal variations in density and temperature give us an idea of what was happening a scant 400,000 years after the Big Bang. We should be able to find information in the CMB about how dark energy affected the formation of galaxy clusters by comparing CMB evidence against what we see in these clusters today. And that makes 'first light' at the National Science Foundation's South Pole Telescope a noteworthy event. The 75-ft tall telescope has been under assembly and testing since November, and its February 16 test run was a success. Now the pole's cold, dry air will allow long-term Earth-based study of the CMB with little interference from water vapor. The Sunyaev-Zeldovich effect, which distorts CMB radiation as it encounters the gases in intervening galaxy clusters, will help scientists...

The night sky has always been a kind of time machine, allowing us to look farther into the past the deeper we look into space. But the heavens are also a time machine in another sense -- by looking carefully, we can find stellar systems in almost every stage of development. We recently saw an example in the Helix Nebula, an object that suggests what our Solar System may look like in five billion years, after the Sun has gone into its red giant phase and then collapsed into a white dwarf. Now have a look at the Sun as it may have been five billion years in the other direction, back when it was coalescing out of its own primordial materials. The Pillars of Creation image taken by Hubble has become iconic, a majestic, breathtaking vista of a star-forming region in M16, the Eagle Nebula. Below, we see a Hubble image of the Pillars overlaid with Chandra X-ray Observatory data showing infant stars being born. Note the bright x-ray sources, most of which are young stars. Much harder to see...

Understanding dark matter, a major goal for cosmology, comes down to figuring out how normal matter interacts with its mysterious counterpart. A vital part of this work may be the objects called dwarf spheroidal galaxies, surely among the most bizarre agglomerations every observed. For current thinking (based on mass-to-light ratios) is that a dwarf spheroidal may be a galaxy composed almost entirely of dark matter. And if that's hard to imagine, consider the problem of researchers trying to observe such objects. A dwarf spheroidal is all but devoid of gas and contains few stars, its normal (baryonic) matter having been stripped away by interactions with larger galaxies. In fact, these ghostly galaxies seem to need larger galaxies in their proximity to form, according to new work by Stelios Kazantzidis (Stanford Linear Accelerator Center), Lucio Mayer (Swiss Federal Institute of Technology) and collaborators. Working with supercomputer simulations, the Kazantzidis team constructed a...