- How do astronomers use Lyman series lines today to study hydrogen gas across the universe?
Astronomical Instruments and Observatories
Telescopes and observatories, historical and modern.
- What job did Henrietta Swan Leavitt hold at the Harvard College Observatory, and how did it shape her discovery?
- How did Shapley's finding rule out the possibility that Cepheid brightness changes were caused by an eclipsing companion star?
- How did Edward Emerson Barnard detect the star's motion by comparing photographic plates taken years apart?
- How did George Ellery Hale and his Mount Wilson colleagues determine that sunspots are regions of intense magnetic field?
- Why did astronomers from Allied nations found the International Astronomical Union in Brussels in July 1919?
- What kinds of nomenclature and measurement standards does the IAU coordinate among the world's observatories?
- Why were Germany and its wartime allies initially excluded from the newly founded IAU?
- How did the IAU's 2006 vote to reclassify Pluto as a dwarf planet provoke such widespread public reaction?
- How did Michelson and Pease use a 20-foot steel beam on the Mount Wilson telescope to measure a star's diameter?
- Why was Leavitt classified as a 'human computer' rather than a scientist during her career at Harvard?
- What role did the 100-inch Hooker telescope play in making Hubble's measurements possible?
- How did Clyde Tombaugh's method of comparing photographic plates actually reveal Pluto's movement?
- Why did the first attempt to cast the Hale Telescope's mirror at Corning fail?
- Why was Palomar Mountain darkened at night during the war years?
- How much did the war delay the completion of the two-hundred-inch telescope?
- How did the completed Hale Telescope change estimates of the size of the observable universe?
- What perturbs objects in the Oort Cloud into orbits that bring them toward the Sun?
- Why has the Oort Cloud never been directly observed despite being widely accepted?
- How did Cyril Hazard use a lunar occultation to pin down the position of 3C 273?
- 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?
- Why did radio astronomers initially call objects like 3C 273 'quasi-stellar radio sources'?
- What did the redshift of 3C 273 imply about its distance and energy output?
- How did Herzberg's spectroscopic catalog of free radicals end up shaping atmospheric chemistry and astrophysics?
- How did James Christy spot Charon as a mere elongation on photographic plates of Pluto?
- What made SN 1987A significant compared to supernovae observed since Kepler's in 1604?
- Why was the saola's discovery considered remarkable for a large land mammal in the late twentieth century?
- What was the first object Chandra imaged, and why did its resolution mark such an advance?
- How did the Marois team use adaptive optics to directly image three planets orbiting HR 8799?
- What technique did the Kalas team use with the Hubble Space Telescope to image a planet around Fomalhaut?
- How many countries participated in the International Year of Astronomy events, and what did they include?
- What made GW170817 the first confirmed multi-messenger astronomical event?
- How quickly did observatories worldwide respond once the gravitational wave and gamma-ray burst were detected?
- Why did it take decades to move from Penrose's theoretical proof to observational confirmation of black holes?
- Why was the phosphine detection on Venus contested and revised after the initial announcement?
- Why is JWST's gold-beryllium mirror designed specifically to detect infrared light?
- Why does the rising detection rate of interstellar objects suggest the interstellar medium contains more of them than previously assumed?
- What astronomical instruments and images relied on CCD technology, from the Hubble Deep Field onward?
- What is the Vera Rubin Observatory designed to do differently from previous sky surveys?