Many stars do not live alone. A binary star is a pair of stars bound by gravity, orbiting a common center of mass. Roughly half of Sun-like stars have at least one companion, and the share is higher for massive stars. Types by how we detect them Visual binaries: both stars can be seen separately … Read more
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 universe is about 13.8 billion years old. That figure comes mainly from measurements of the cosmic microwave background, and it is supported by independent checks on the oldest objects we can see. Method 1: the cosmic microwave background The cosmic microwave background is light released about 380,000 years after the Big Bang. The size … Read more
Stars are usually born in groups. A star cluster is a family of stars that formed from the same cloud at about the same time, so they share a similar age and chemical makeup. This makes clusters ideal laboratories for studying how stars evolve. Open clusters Famous examples: the Pleiades (the Seven Sisters), visible to … 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
Gravitational waves are ripples in the fabric of space-time, produced when massive objects accelerate. Einstein predicted them in 1916 but thought they would be too weak to detect. A century later, he was proven right on the first point and wrong on the second. The first detection On September 14, 2015, the two LIGO detectors … 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
Every star is born in a cloud of gas and dust and spends its life in a balance between gravity, which pulls inward, and the pressure of nuclear fusion pushing outward. Its mass at birth decides how long it lives and how it dies. Birth in molecular clouds Stars form in cold, dense clouds of … Read more
