12+ hour, 57+ min ago   (282+ words) Dark photons are one proposed explanation for dark matter. A new calculation suggests that the early universe’s plasma may have stopped them from depositing heat as efficiently as earlier models predicted. The post Early-Universe Plasma May Have Kept Dark Photons…...

14+ hour, 28+ min ago   (663+ words) The cosmic microwave background is the oldest light we can observe. Here is where it came from, what its tiny patterns reveal, and why it still matters. About 380,000 years after the Big Bang, the expanding universe had cooled enough for…...

3+ day, 9+ hour ago   (1153+ words) The objects are unusually soft in X-rays but bright in extreme ultraviolet light—exactly the combination that makes them difficult to find and potentially important to the history of stars and galaxies. A galaxy can be full of powerful objects…...

5+ day, 15+ hour ago   (559+ words) In empty space, light travels at exactly 299,792,458 meters per second. That is about 300,000 kilometers per second, or 186,282 miles per second. It is the fastest speed at which matter, energy, or information can travel through the universe. The number is so…...

1+ week, 2+ day ago   (752+ words) A parsec is a distance defined by parallax. Here is how astronomers use the unit to measure the space between stars and galaxies. What is a parsec? It is a unit of distance used by astronomers to describe the space…...

1+ week, 4+ day ago   (268+ words) Einstein’s theory of general relativity has survived another demanding test. Researchers used clouds of ultracold atoms aboard China’s space station to compare how two forms of rubidium respond to gravity, and found no measurable difference between them. Before your next…...

1+ week, 5+ day ago   (453+ words) Astronomers often treat the thin streams of stars around the Milky Way as sensitive tracers of dark matter. A new University of Washington simulation shows why that evidence needs to be read carefully: the visible structure of a galaxy can…...

2+ week, 15+ hour ago   (754+ words) The explosion is not simply a large firework at the surface. In a massive star, the core has been building heavier elements through nuclear fusion. When the core reaches iron, fusion can no longer provide the energy needed to support…...

2+ week, 5+ day ago   (711+ words) They use a chain of methods rather than one universal measuring tape. Radar can reach planets. Parallax works for nearby stars. Farther out, astronomers compare known brightnesses, stellar pulsations and the stretching of light. Each step is checked against the…...