A quasar is the extremely bright core of a distant galaxy, powered by a supermassive black hole swallowing gas. A single quasar can outshine all the stars of its host galaxy combined, which makes quasars visible across billions of light-years. How quasars were found In the 1950s, radio astronomers found sources that looked like stars … Read more
No one has drilled into Jupiter or breathed the air of a planet around another star. Yet astronomers know a surprising amount about what planets and their atmospheres are made of, by combining several methods. Density: rock, ice or gas? If you know a planet’s mass (from the orbits of its moons, or how it … Read more
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
According to Einstein’s general relativity, mass curves space, so light passing near a massive object follows a bent path. A galaxy or cluster can act like a giant, imperfect lens that magnifies and distorts the light of objects behind it. A famous confirmation During the total solar eclipse of 1919, expeditions led by Arthur Eddington … 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
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
A supernova is the explosion of a star, briefly bright enough to outshine an entire galaxy. These explosions forge and scatter many of the elements in our bodies and planets, and leave behind neutron stars and black holes. Two main kinds Core-collapse supernovae (Types II, Ib and Ic) happen when a massive star, more than … Read more
The Moon does not make its own light. It reflects sunlight, and half of it is always lit by the Sun. As the Moon orbits Earth, we see different portions of that lit half. That changing view creates the phases. The eight phases “Waxing” means growing and “waning” means shrinking. How long is the cycle? … Read more
A nebula is a cloud of gas and dust in space. Some are nurseries where new stars form, others are the remains of dying or exploded stars. They are classified mainly by how they shine, or fail to. Emission nebulae Hot, young stars flood nearby hydrogen gas with ultraviolet light. The gas is ionized and … 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
