The three words are often used interchangeably, and the boundaries really are blurry. Still, each has a distinct emphasis. Astronomy: observing the sky Astronomy is the oldest of the natural sciences. It studies everything beyond Earth’s atmosphere: planets, stars, galaxies and more. Historically, it focused on measuring and observing: positions, motions, brightness and distances. Ancient … Read more
The Sun is an ordinary star but the center of everything in our solar system. Its gravity holds the planets in orbit, its light and heat make life on Earth possible, and its activity affects space all the way to the edge of the heliosphere. Gravity: the anchor The Sun contains about 99.8 percent of … Read more
A solar flare is a sudden, intense burst of radiation from the Sun’s surface, released when tangled magnetic fields near sunspots snap and reconnect. A large flare can release as much energy as billions of nuclear bombs in a few minutes. Flare classes Flares are ranked by their peak X-ray brightness, measured by satellites. Each … Read more
Despite the name, cosmic rays are not rays of light. They are high-energy particles, mostly atomic nuclei, that travel through space at nearly the speed of light and constantly hit Earth’s atmosphere. How cosmic rays were discovered In 1912, Austrian physicist Victor Hess carried instruments up in a balloon and found that radiation increased with … 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
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
An exoplanet is a planet orbiting a star other than the Sun. The first ones were confirmed in the 1990s, and the NASA Exoplanet Archive now lists more than 6,000. Most are never seen directly: they are detected through their effects on their star. The transit method When a planet passes in front of its … Read more
Comets and asteroids are both leftovers from the formation of the solar system about 4.6 billion years ago. The main difference is what they are made of, which determines how they behave near the Sun. Asteroids: rock and metal Comets: dirty snowballs Famous comet: Halley’s Comet returns about every 76 years and is next expected … Read more
How the universe will end depends mainly on dark energy, the mysterious component that is making the expansion of space speed up. Nobody knows for sure, but current observations point toward a long, cold fade. The discovery that changed everything In 1998, two teams studying distant Type Ia supernovae found that they were dimmer than … Read more
