- Why did the stars in the Small Magellanic Cloud provide Leavitt with a reliable way to compare absolute stellar brightness?
Galaxies and Large-Scale Structure
The formation, dynamics, and clustering of galaxies.
- Why was the nature of the Andromeda nebula such a contested question in 1913?
- What did Hubble's 1924 distance measurement to Andromeda's Cepheids ultimately prove about the Milky Way?
- How did Shapley later use Cepheid distances to argue that the Sun sits far from the center of the Milky Way?
- How did Harlow Shapley use Cepheid variable stars to measure distances to globular clusters?
- What did Shapley's mapping of globular clusters reveal about the Sun's position in the Milky Way?
- How did Edwin Hubble use Leavitt's relation to prove the Andromeda nebula lay outside the Milky Way?
- What was the Great Debate of 1920, and what were the two competing views of the Andromeda nebula?
- How far did Hubble calculate Andromeda to be, and why did that distance settle the debate?
- How did Jansky determine that the persistent radio hiss was coming from the direction of the galactic centre?
- What later astronomical discoveries grew out of the field of radio astronomy that Jansky's antenna founded?
- What did the 15.8% redshift in 3C 273's spectrum reveal about its distance from Earth?
- Why did 3C 273's brightness at such a vast distance imply a supermassive black hole?
- What did the discovery of quasars suggest about how violent the early universe was?
- Why did radio astronomers initially call objects like 3C 273 'quasi-stellar radio sources'?
- How did Maarten Schmidt realize the strange emission lines in 3C 273's spectrum were actually redshifted hydrogen?
- What do astronomers now understand to be powering quasars?
- How is the Kerr metric still used in modern black hole observations like the Event Horizon Telescope?
- What was the Arecibo Message, and why was it aimed at the globular cluster M13?
- What new kinds of astronomical objects did the Einstein Observatory reveal that earlier X-ray detectors could not?
- How did Ian Shelton first notice Supernova 1987A at Las Campanas Observatory?
- Why did the small temperature anisotropies detected in 1992 matter for explaining how galaxies formed?
- Why were the tiny temperature fluctuations COBE detected so significant for understanding galaxy formation?
- How did polarised galactic dust end up mimicking the signature of primordial gravitational waves?
- How did linking eight radio observatories across four continents effectively turn Earth into a single telescope?
- What black hole did the Event Horizon Telescope image, and how far away is it?
- What does the orange ring in the black hole image actually show, and what does the dark centre represent?
- How did Genzel and Ghez track individual stars to prove something massive and invisible sits at the centre of the Milky Way?
- How much mass is packed into Sagittarius A*, and how small is the volume it occupies?
- What five images did NASA release on 12 July 2022, and what did each one show?
- What has Gaia's data revealed about the Milky Way's merger history and stellar streams?