Entries by Mark R Smith

Supernova Refsdal: Multiply-Imaged Supernova Explained

Supernova (SN) Refsdal — Key Points Astronomers have been trying to understand space for thousands of years. Supernova Refsdal was the first known multiply-imaged supernova. Multiple images of the supernova are produced by strong gravitational lensing. Astronomers predicted the reappearance of the supernova before it was observed. The multiple images of the supernova exhibit measurable…

Evidence for the Big Bang: CMB, Hubble’s Law, FAQ Guide

Big Bang: Key Points Hubble’s law (redshift of galaxies) and the Doppler effect provide direct evidence that the universe is expanding away from our reference point. Expansion has cooled the universe from the initial high temperatures at the Big Bang; radio astronomy detects signals from stars, galaxies, radio galaxies, quasars, and pulsars that trace this…

Cosmic Web Connectivity: Galaxy Evolution and Quenching

The universe was not perfectly uniform at the beginning; some regions had higher density than others. Over time these higher-density regions attracted most of the matter and began forming galaxies where matter concentration was greatest. The resulting large-scale structure—the “cosmic web”—connects observed galaxy clusters with a network of filaments. Figure 1 shows a model of…

Gaia Astrometry: Detecting Gravitational Waves Effectively

Gravitational waves (GWs) are disturbances in spacetime produced by massive objects moving asymmetrically. Only the most massive and most relativistic systems produce GWs large enough to be detectable. The Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo detectors use laser interferometry to detect tiny ripples in the fabric of spacetime; they have already detected dozens of…

Mary Somerville: Scottish Polymath & RAS Honorary Member

Google Doodle: Mary Somerville and Caroline Herschel The Google Doodle for 2 February 2020 celebrated Mary Somerville, the Scottish polymath and science writer, and Caroline Herschel, jointly the first women to be made honorary members of the Royal Astronomical Society (RAS). Early life and education Born in Jedburgh, Scotland, in 1780, Somerville received little formal…