Astronomy Glossary

Galaxies

An Active Galactic Nucleus is a compact, extraordinarily luminous central region of a galaxy powered by accretion onto a supermassive black hole.

Cosmology Universe

The Big Bang theory describes the Universe's evolution from an extremely hot, dense initial state ~13.8 billion years ago, expanding and cooling to th...

Galaxies

Blazars are AGN with relativistic jets pointed directly at Earth, producing extreme luminosity, rapid variability, and strong polarization.

Cosmology Universe

Cosmic horizons define boundaries beyond which information cannot reach us due to finite light speed and Universe's expansion history.

Cosmology Universe

Cosmic inflation is a period of exponential expansion in the first 10^-36 to 10^-32 seconds after the Big Bang, proposed to solve several cosmological...

Cosmology Universe

The Cosmic Microwave Background is the thermal radiation from 380,000 years after the Big Bang, when Universe cooled enough for neutral atoms to form ...

Galaxies

The cosmic web is the large-scale structure of the Universe, consisting of filaments of galaxies surrounding vast empty voids, resembling a sponge-lik...

Cosmology Universe

Dark energy is a mysterious component causing the Universe's expansion to accelerate, comprising ~68% of the Universe's energy density.

Cosmology Universe

Dark matter is non-luminous matter detectable only through gravitational effects, comprising ~85% of matter in the Universe.

Galaxies

Galaxy clusters are the largest gravitationally bound structures in the Universe, containing hundreds to thousands of galaxies plus hot intracluster g...

Stellar Objects

A hypernova is an exceptionally energetic supernova (10-100× normal), producing relativistic jets and associated with long-duration gamma-ray bursts.

Cosmology Universe

The ΛCDM model (Lambda Cold Dark Matter) is the standard cosmological model describing Universe's large-scale structure and evolution.

Stellar Objects

A magnetar is a neutron star with an extraordinarily powerful magnetic field (10^14-10^15 Gauss), the strongest magnetic fields known in the Universe.

Stellar Objects

A neutron star is the ultra-dense remnant of a massive star's supernova explosion, composed almost entirely of neutrons and supported by neutron degen...

Solar System

The Oort Cloud is a hypothetical spherical shell of icy planetesimals surrounding the Solar System at extreme distances (2,000-100,000 AU), serving as...

Astronomy Concepts

Polarization describes the orientation of electromagnetic wave oscillations, providing unique astrophysical diagnostics unavailable from intensity alo...

Stellar Objects

A pulsar is a highly magnetized, rapidly rotating neutron star that emits beams of electromagnetic radiation from its magnetic poles.

Galaxies

Quasars (quasi-stellar radio sources, though most aren't radio-loud) are the most luminous persistent objects in the Universe, powered by supermassive...

Astronomy Concepts

Radiation pressure is the force exerted by electromagnetic radiation on matter, important for understanding stellar structure and astrophysical dynami...

Units Distance

Redshift quantifies how much light has been stretched to longer (redder) wavelengths, serving as both a velocity and distance indicator.

Galaxies

Seyfert galaxies are spiral galaxies with bright, compact nuclei showing strong emission lines, a nearby moderate-luminosity class of AGN.

Cosmology Universe

A singularity in General Relativity is a point where spacetime curvature becomes infinite and physical laws break down.

Telescopes Equipment

Solar filters provide the ONLY safe way to observe the Sun through telescopes or binoculars, protecting eyes from permanent retinal damage.

Galaxies

Starburst galaxies undergo exceptionally intense star formation at rates 100-1,000× higher than normal galaxies, consuming gas rapidly.

Galaxies

Superclusters are massive structures containing multiple galaxy clusters and groups, spanning hundreds of millions of light-years, though not gravitat...

Stellar Objects

A supernova is a catastrophic stellar explosion, briefly outshining entire galaxies and producing most elements heavier than iron.