SUNSET: 
New Eyes on the Cosmic-Ray Sky
High on the Argentinian pampa, 1,600 water-filled "eyes" await the arrival of the most powerful high-energy particles in the universe.
Hubble Finds a Mystery Object
What was it? While monitoring a cluster of galaxies, the Hubble Space Telescope recorded what seems like a new class of astronomical object brightening and fading over six months.
Lensed Light Used to Weigh Dark Matter
Astronomers use a novel method of weighing distant galaxies to measure their masses and find that there's more matter than the galaxies' light can easily explain.
Dark Energy's Early Fingerprints
Studying the effect of galaxy clusters on the background radiation from the early universe, University of Hawaii astronomers have added to the pile of evidence for dark energy.
A Galactic Dead Zone
Astronomers find that the organic compounds common throughout our galaxy and others suddenly disappear along M101's outer edge.
Weighing Black Holes with a Thermometer
Astronomers use the 12-million-kelvin-blaze of a galaxy's central region to measure its supermassive black hole.
Faint Supernovae Remain Unexplained
A subclass of supernovae that fades much faster than expected reveals possible kinks in astronomers' theories of what causes these explosions.
Hubble Looks into the Coma Cluster
The HST captures a pristine image of various galaxy types grouped together, but what is most intriguing is what the image doesn't reveal.
Hubble's Colliding Galaxies
No two galaxy collisions are alike, as shown in 59 weird images just released by the Hubble Heritage Project.
A Record-Breaking Gamma-Ray Burst
The visible-light glow of a gamma-ray burst briefly shone at magnitude 5.4, despite its distance of 7.5 billion light-years — more than halfway across the visible universe.
Standard-Candle Supernova Confusion
Type 1a supernovas are crucial for measuring how the expansion of the universe has been changing. But no one knows for sure exactly what they are.
Monster Black Holes Soon to Collide?
The members of a binary black hole in Cancer, one of which is unbelievably massive, look to be on a collision course.
Astronomers Find Double Einstein Ring
A unique example of gravitational lensing in the universe gives clues to the distribution of dark matter in galaxies.
Cold Evidence for a Cosmic "Texture"?
A ripple in the cosmic background radiation hints at an irregularity in spacetime. . . maybe.
Refining Hipparcos's Star Distances
To extract even better star distances, a Cambridge astronomer who took part in the Hipparcos mission has just completed a whole new analysis of the raw data.
Mystery Pulse from Outer Space
Six years ago a radio telescope in Australia recorded a mysterious radio burst that lasted only a tiny fraction of a second and reached Earth from more than a billion light-years away. Astronomers have no idea what caused it.
Finding the Missing Dwarf Galaxies
Minigalaxies of dark matter ought to be everywhere, says the best theory of how the universe came to be. Now they're finally being found.
A Whole Lotta Nothing
If you're looking for a place to really get away from it all, head toward a lovely spot in southeastern Eridanus.
Whole Lot of Nothing
A billion light-year-wide "hole" in space is a very cold and empty place.
"Magnificent" Neutron Star Found
Sizzling with X-rays but mum at radio frequencies, a nearby, on-its-own neutron star is causing astronomers to scratch their heads.
