The James Webb Space Telescope (JWST) is the largest and most powerful space telescope ever built. A partnership between NASA, the European Space Agency and the Canadian Space Agency, it launched on December 25, 2021 (NASA’s Webb mission page) and began science operations in July 2022. Key features Why infrared? Main discoveries so far Webb … Read more
Spectroscopy means spreading light into its colors, a spectrum, and studying it in detail. It is one of the most powerful tools in astronomy: from a point of light, it can reveal what a star is made of, how hot it is, how fast it moves and much more. Spectral lines: chemical fingerprints Every element … Read more
Polaris, the North Star, is not the brightest star in the sky. It ranks only around 50th. Its importance comes from its position: it lies almost exactly above Earth’s North Pole, so it barely moves while the rest of the sky turns around it. Why it seems fixed Earth rotates around an axis. Extend that … Read more
A constellation is a pattern of stars that people have linked together and named. For astronomers today, it is also an official region of the sky, like a country on a map, so that every star and galaxy belongs to exactly one constellation. Stars in a constellation are not neighbors The stars of a constellation … Read more
Astronomy is probably the oldest science. People watched the sky to keep time, plan harvests, navigate and make sense of their place in the world long before writing existed. Ancient skywatchers Greek models Greek thinkers sought geometric explanations. Eratosthenes estimated Earth’s circumference around 240 BCE. Aristarchus proposed that Earth orbits the Sun, but the Earth-centered … Read more
Almost everything we know about the universe comes from light. A telescope’s main job is not to magnify but to collect as much light as possible and focus it into an image. Refractors and reflectors An eyepiece or a camera then magnifies or records the focused image. Aperture is what counts Seeing through the atmosphere … Read more
Since Sputnik in 1957, space exploration has achieved astonishing things: humans on the Moon, rovers on Mars, probes beyond the heliosphere. But every mission still faces hard problems, and sending people farther than the Moon multiplies them. Radiation Beyond Earth’s protective magnetic field, astronauts are exposed to galactic cosmic rays and solar particle events, which … Read more
You cannot run a tape measure to a star. Astronomers instead use a chain of methods, the cosmic distance ladder, where each step calibrates the next, reaching from nearby planets to the edge of the observable universe. Units Step 1: radar in the solar system Bouncing radar off Venus and other planets and timing the … Read more
