Astronomy & Cosmology

A Journey Through the Universe

From our solar system to the frontiers of the observable — from familiar to breathtaking.

01 · Fundamentals

The Solar System

Eight planets, hundreds of moons, thousands of asteroids and billions of comets — all bound to a single star. The solar system is the cosmic home we know best, and yet still don't fully understand.

Beginner
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M V E Ma J 8 planets · 1 star · 4.6 billion years
02 · Stars

Stars & Their Life Cycle

A star lives because gravity and radiation pressure are in balance. The Hertzsprung-Russell diagram shows at a glance where every star stands in its evolution — from formation to supernova, or a quiet fade into darkness.

Fundamentals
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O · B · A · F · G · K · M (hotter ←) Luminosity ↑ O B G K M Main sequence Red giant White dwarf ☉ Hertzsprung-Russell diagram
03 · Structures

Galaxies

Galaxies are the building blocks of the universe — vast islands of hundreds of billions of stars, gas, dust and dark matter. Spirals, ellipticals, dwarf galaxies: each tells a story of formation, collision and cosmic time.

Fundamentals
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Spiral galaxy Milky Way (SBbc) Elliptical galaxy Type E · Old stars Irregular galaxy Irr · Magellanic Clouds Hubble classification — hundreds of billions of galaxies in the observable universe
04 · Cosmology

The Universe

13.8 billion years of history in one model: ΛCDM. From the Big Bang through cosmic inflation and recombination to today's accelerating expansion. What we can see directly is only 5% of everything there is.

Intermediate
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Big Bang t = 0 Inflation CMB 380,000 years First stars 200 million years Today 13.8 billion yrs ΛCDM · Standard cosmological model
05 · Extremes

Black Holes

Where spacetime is curved so intensely that not even light can escape. Black holes are the most extreme objects of general relativity — and since 2019, they've even been photographed. What happens beyond the event horizon?

Intermediate
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Jet Photon sphere Event horizon · General relativity
06 · Mystery

Dark Matter & Energy

95% of the universe consists of something we cannot see, cannot touch and cannot measure directly. Dark matter holds galaxies together. Dark energy drives the expansion. Both remain the biggest mystery in modern physics.

Advanced
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Dark matter (halo · invisible) Einstein ring Galaxy Q Q Gravitational lensing · 95% of the universe is invisible
07 · Life

Exoplanets & Astrobiology

Over 6,000 confirmed planets beyond our solar system. Some of them lie in their star's habitable zone — where liquid water could exist. Whether we are alone in the universe is one of the deepest questions we can ask.

Intermediate
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Habitable zone L Transit Transit method · 6,000+ confirmed exoplanets
08 · Frontiers

Cosmological Frontiers

Inflation, the multiverse, the end of time — at the outermost edges of knowledge, cosmology becomes speculation grounded in mathematics. What came before the Big Bang? What exists beyond the observable horizon? And how does the universe end?

Complex
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Beyond · Multiverse ? Observable universe Local group Milky Way Solar system ? ? ? Cosmology · What lies beyond the horizon?