SUNSET: 
Direct Evidence of Big Bang Inflation
Researchers with an experiment based at the South Pole have discovered the long-sought "smoking gun" for inflation. The signal was hidden in polarization patterns in the cosmic microwave background and confirms physicists' audacious theory of how the Big Bang happened.
"Proof of Inflationary Universe" to be Announced
Rumors are flying that the long-sought "smoking gun" for inflation has been found in polarization patterns in the cosmic microwave background. If so, it would confirm the inflation theory for how and why the Big Bang happened.
Hubble Displays Galactic Jellyfish
These stunning new images of spiral galaxy ESO 137-001 highlight its violent encounter with the intracluster plasma of Abell 3627, which is stripping away its gas and forming stars in the streamers.
Rocky Encounter with Stellar Lighthouse
Asteroid debris might be bombarding a radio pulsar in the constellation Puppis.
Mystery of the Missing Galaxy Clusters
Astronomers have counted up the number of galaxy clusters in the cosmos and found a problem: the number is much lower than they expected. What's going on?
Lighting Up the Cosmic Web
A rare alignment of a quasar’s “flashlight” beam and a filament of the cosmic web illuminates the universe’s large-scale structure.
New View of Lagoon Nebula
A new image of the Lagoon Nebula from the Paranal Observatory in Chile provides a stunning view the iconic object, which lies 5,000 light-years from Earth in Sagittarius.
Galaxies Grow By Snacking
Evidence from observations and computer simulations supports a picture of galaxy growth that isn't dominated by the rough-and-tumble crashes of big galaxies. Instead, most of the universe's stellar metropolises appear to feed themselves with nibbles instead of feasts.
Galaxies Trace Early Cosmic History
Astronomers have used the Hubble Space Telescope to peek into the universe's early eras using the light from galaxies that existed several hundred million years after the Big Bang.
Cosmologist Halton Arp (1927-2013)
A contentious yet gifted astronomer, Arp challenged a key underpinning of the Big Bang throughout the 1970s and 1980s and ultimately fell into disfavor among his colleagues.
Exotic Stellar Trio Includes Pulsar
Imagine a three-star system with two white dwarfs and a wildly spinning, superdense neutron star, all packed within a space no bigger than Earth's orbit.
Gaia Launches to Pinpoint a Billion Stars
Gaia launched flawlessly Thursday morning at 9:12 UTC (4:12 a.m. Eastern Standard Time). This long-awaited mission will precisely map the distances and motions of 1 billion stars in our galaxy.
Triple Collision in Infant Galaxy
A complex of three bright, star-forming clumps called Himiko is merging in the early universe. With its light reaching us from when the universe was only 800 million years old, this primordial galaxy could yield insight into the elusive process of early galaxy formation.
Two Blows for Dark Matter Model
Two recent experiments limit physicists’ favorite candidate for the elusive and invisible matter lurking in the universe.
A Galaxy Near Cosmic Dawn
Astronomers have confirmed that light from a distant galaxy is reaching us from about 700 million years after the Big Bang. The galaxy's emission hints that star formation during that era might have proceeded at a much faster rate than previously thought.
Planck Spacecraft Shut Down
After four years of exquisite observations, the latest mission to study the universe's earliest light has been shuttered. But this end is a happy one and comes with a significant cosmological legacy.
Seeking the Cosmic Dawn
Astronomers have finally detected a much-hoped-for pattern in the afterglow of the Big Bang, and it might help reveal inflation's signature.
Mystery Signals from Space
Four powerful radio bursts have left astronomers scratching their heads. The bursts appear to come from several billion light-years away and could provide a whole new look at the universe — but observers aren't sure what they are.
Universe's Lithium Problem A Bit Better
Studies of primitive stars suggest the universe has far too little of one form of lithium and far too much of another. But new work shows that the second problem might be nonexistent.
Weighing in on Einstein's Gravity
A massive neutron star and its lightweight sidekick provide a unique space laboratory to test general relativity. So far, gravity keeps behaving as it's supposed to.