It packs 4 million times more material than our sun, but relative to the black holes sitting at the center of some neighboring galaxies, it actually doesn't do all that much. The fact that this black hole, known as Sagittarius A*, kicks out billions of times less energy than others of its kind has made it something of a mystery. But now a team of scientists at Kyoto University suggests that Sagittarius A* may be resting after a far more active period a few centuries ago.

What's cooler than a black hole? Two of them, rotating around and then crashing into one another. And what could be more entertaining than that cataclysmic cosmic dance? Why, one more, of course.

A team of scientists at the Rochester Institute of Technology has simulated the merger of three black holes.

Ultra-high-energy cosmic rays carry more energy than any known particles in the universe, so we should probably all take it as good news that scientists have confirmed that they don't originate in our cosmic neighborhood. In fact, the majority of these rays—which are mostly hydrogen and helium—lose most of their juice on their way towards Earth because they interact with the cosmic microwave background radiation, the energetic leftover of the Big Bang.

Black holes are notoriously difficult to observe. They can’t be seen directly by a telescope because they absorb all light. We’re only able to tell they’re out there by the way they bend and heat the gasses around them. But we can, however, think up analogues which approximate some of the mechanics, which is what a team at the University of St. Andrews in Scotland has done, using just a length of fiber optics.

A black hole wreaks all sorts of havoc in its cosmic neighborhood, pulling in and stretching out matter, spewing jets and slowing time to a near stand-still. Now astrophysicists have added a new phenomenon to the black hole's list of tricks: Light echoes.

Black holes are often surrounded by spinning discs of burning gas that can emit X-ray bursts. Because the black hole warps the surrounding space-time so intensely, though, the photons from a single one of these bursts don't always arrive at the same time. Read more on the new phenomenon, announced at this week's American Astronomical Society Meeting, here.—Gregory Mone

For decades scientists have been speculating about the origin of ultra-high energy cosmic rays, the incredibly powerful charged particles that travel across the cosmos, then set off a series of reactions as they smash through Earth's atmosphere. They're extremely rare, showing up only once per century for a given square mile.

Now astrophysicsts using the Pierre Auger Observatory in Argentina, which has detectors spread across 1,200 square miles, recently reported that they traced the rays back to their source. It appears likely that cosmic rays are born within active galactic nuclei. These galaxies, which have massive black holes at their centers, are busily churning up stars, gas and dust, generating hugely energetic reactions. The ultra-high energy rays are just one of the products. The work is published in the latest issue of the journal Science.—Gregory Mone

If we wish to travel through time, we must be able to control it, to mold it to our own desires and specifications. This is possible only through Einstein's theory of relativity. Instead of imagining space as an immutable structure, part of Einstein's genius was realizing that space and time are interlinked in a single, pliable framework called space-time. Both space and time can be distorted, sometimes dramatically. Time travel requires nothing more than exploiting those distortions to create a path through time that ends earlier—or much later—than it begins.