What is dark matter?
Galaxy rotation, lensing and cosmic structures point to additional mass. Follow those lines of evidence and distinguish them from the search for unknown particles.
Tag archive
#galaxies
Articles: 9
Why do we see distant galaxies as they were in the past?
Light brings earlier events with a delay. Distinguish light travel time, galaxy age and present distance in an expanding Universe.
What is the cosmic web?
How galaxies, gas and dark matter form nodes, filaments and voids, what sky surveys measure, and how a map differs from a simulation.
What happens if the Milky Way meets Andromeda?
Possible flybys and mergers, stellar orbits and gas. Why the forecast depends on transverse motion and how the 2025–2026 studies differ.
How many galaxies are there in the Universe?
Why hundreds of billions and two trillion are not two exact censuses: deep fields, telescope sensitivity, faint galaxies and the limits of estimation.
How do we measure the distance to another galaxy?
How Cepheids, geometric anchors and Type Ia supernovae transfer the scale along the cosmic distance ladder, and why standard candles require calibration.
Why do galaxies have different shapes?
How rotation, cooling gas, stellar orbits and interactions create different galaxies, and why the same disk looks different edge-on.
Where are we in the Milky Way?
The solar system in the disk and Local Arm: distance to the center, our inside view of the Galaxy, and the measurements used to build its map.
What is a galaxy?
Why a galaxy is more than a patch of light: stars, gas, dust, shared gravity and evidence for dark matter. How to distinguish observation from inference.