Journey through the universe
Travel outward from Earth past the planets, the stars and the Milky Way to the cosmic web and the edge of the observable universe, drawn from real star and…
Crevasses
Cracks in the ice, a metre or two wide, open where the glacier is pulled apart as it flows.
Near the surface glacier ice is brittle; deeper down it flows like a very slow, stiff fluid, so crevasses rarely reach much deeper than about 30 m before they close. The dark band is a medial moraine: rock from the edges of two glaciers, carried along as one stripe after they merged.
What you’re seeing: Aerial photographs by swisstopo, 25 cm to a pixel.
Aletsch Glacier
The largest glacier in the Alps, about 23 km long. Four glaciers feed it at Konkordiaplatz, where the ice is over 900 m deep.
It holds about 15 km³ of ice, but like most glaciers it is shrinking: since 1870 it has thinned by more than 300 m, and between 1980 and 2016 it lost 1.3 km of its length. The dark stripes are rock carried from the edges of the glaciers that merged. The area has been a UNESCO World Heritage Site since 2001.
What you’re seeing: Aerial photographs by swisstopo, blending into the Sentinel-2 satellite mosaic. The cumulus are real clouds cut from a Sentinel-2 image and set at the height where they form.
The Alps
Europe’s highest mountains, an arc about 1,200 km long. The camera is heading for a glacier in the middle.
The Alps rose as the African plate pushed into Europe, and the ice ages carved their valleys. The white patches are glaciers and snow that lasts through the summer; the largest glacier of all is the Aletsch, in Switzerland.
What you’re seeing: The Sentinel-2 cloudless mosaic, stitched from many clear days.
Earth
Our home planet, 12,742 km across. Every distance on this journey is measured from here.
Earth is the only place known to host life. At this scale its air is a thin line along the edge: nine-tenths of it lies within 16 km of the ground, a thousandth of the planet’s width.
What you’re seeing: Earth as it is turned today, from satellite mosaics, a day of NASA cloud maps and city lights on the night side. The aurora is drawn as in a strong storm.
Near-Earth space
Satellites circle Earth inside a magnetic bubble that holds off the wind of particles from the Sun.
The International Space Station orbits 420 km up, once every 90 minutes. GPS satellites fly at about 20,000 km, and at 35,786 km a satellite goes round once as Earth turns once, so it seems to hang over one spot. Earth’s magnetic field stops the solar wind about 60,000 km out on the day side and trails into a long tail on the night side.
What you’re seeing: Orbits to scale, in one plane. The blue glow is the plasmasphere, the amber the Van Allen radiation belts and the violet the magnetosphere: all invisible to the eye, shown in false colour.
Earth & Moon
The Moon circles Earth about 384,000 km away, roughly 30 Earths lined up.
Light crosses the gap in just over a second. The Moon, a quarter of Earth’s width, drifts 3.8 cm farther away each year. In April 2026 the Artemis II crew went 406,778 km from Earth, farther than anyone before. The James Webb telescope works four times farther out, where the pulls of Earth and the Sun together keep it circling the Sun in step with Earth.
What you’re seeing: Orbits to scale, with the Moon where it is today.
Sun & inner planets
The Sun holds 99.8% of the Solar System’s mass. Earth orbits it 150 million km away: one astronomical unit (au).
Sunlight takes about 8 minutes to reach Earth. Mercury, Venus, Earth and Mars are small rocky worlds. Venus, not Mercury, is the hottest of them, its thick carbon dioxide air trapping the heat.
What you’re seeing: Planets where they are today, on orbits simplified to circles. The golden glow, sunlight scattered by dust, is exaggerated.
Asteroid belt & Jupiter
Between Mars and Jupiter orbit millions of rocky leftovers that never became a planet. Jupiter outweighs all the other planets together.
All the asteroids together hold only about 3% of the Moon’s mass, spread so thin that spacecraft cross the belt without steering round anything. Jupiter’s gravity clears gaps in the belt and herds two swarms of asteroids, the Trojans, 60 degrees ahead of it and behind it on its orbit.
What you’re seeing: The belt and the Trojans are illustrative particles, not individual asteroids; the gaps in the belt are at their real distances.
Solar System
Eight planets, then the icy Kuiper Belt. Neptune orbits 30 times farther from the Sun than Earth does.
Sunlight takes four hours to reach Neptune. Beyond it, the Kuiper Belt holds Pluto and other dwarf planets among countless icy bodies. Some follow long, tilted orbits: Eris swings out to almost 100 times Earth’s distance from the Sun.
What you’re seeing: Dwarf planets on their real orbits, planets on circles.
Heliosphere
The solar wind blows a bubble into the gas between the stars. Its edge, the heliopause, lies about 120 au from the Sun.
The wind leaves the Sun at around 400 km/s, slows abruptly at the termination shock, near 90 au, and stops at the heliopause. Voyager 1 crossed it in 2012 and Voyager 2 in 2018. Voyager 1 is now about 170 au away; its signal takes almost a day to reach us.
What you’re seeing: The boundaries stand where both Voyagers crossed them; the tail follows a simple model and its shape is still debated. Colours are chosen for clarity.
Sedna
Sedna never comes closer to the Sun than 76 au and swings out to about 900 au. One lap takes 11,000 years.
Nothing in the Solar System today could have pulled it onto such an orbit. A star passing the young Sun may have done it, or an undiscovered planet far out: a handful of bodies on similar orbits, such as Leleākūhonua, have sent astronomers looking for one.
What you’re seeing: Sedna, Leleākūhonua and a long-period comet on their real orbits.
Oort Cloud
A vast shell of icy bodies thought to surround the Sun, reaching perhaps 100,000 au, more than a light-year and a half.
No object has been seen in the Oort Cloud itself; it is inferred from comets that fall toward the Sun from every direction. Voyager 1 would need about 300 years to reach its inner edge and some 30,000 years to cross it.
What you’re seeing: The cloud is an illustrative glow. The stars are real, at their measured positions.
Solar neighborhood
The nearest stars. Proxima Centauri, 4.2 light-years away, is our closest neighbor.
About 370 stars.
Most of those stars are faint red dwarfs, and not one can be seen with the naked eye. Only a few neighbors, such as Sirius (8.6 light-years) and Vega (25), are bright in our sky. Our first radio broadcasts, from the 1920s, have now travelled about 100 light-years.
What you’re seeing: Real stars at their measured positions, seen in perspective from above the Sun, so nearer stars spread wider. Dot size shows brightness. Many faint red dwarfs are missing. The pale cloud around the Sun is the Local Interstellar Cloud, its outline drawn.
Local Bubble
The Sun sits in a cavity about 1,000 light-years across, blown out by supernovae over the last 14 million years.
About a million stars.
The explosions swept gas and dust into a shell, and where the shell is densest new stars form: every star-forming cloud within about 500 light-years lies on its surface. The Pleiades, 440 light-years away, are one of the young clusters nearby.
What you’re seeing: The star-forming clouds are at their measured places; the wall between them is drawn. The hot gas inside glows only in X-rays, shown in false-colour violet.
Orion Arm
The Sun lies in the Orion Arm, a minor spiral arm of the Milky Way.
About 100 million stars.
Spiral arms are not fixed: stars and gas pass through them like cars through a traffic jam. The brightest stars burn out before they drift far from where they were born, so they light the arms up. The Orion Nebula, 1,300 light-years away, is making stars right now.
What you’re seeing: Real hot young stars and Cepheids from Gaia-based catalogs. The pink knots of glowing gas are placed along the arms, not mapped.
Milky Way
Our galaxy: a disk of stars about 100,000 light-years across.
100 to 400 billion stars.
The Sun lies about 26,600 light-years from the center and takes around 230 million years to go round it once. At the center sits Sagittarius A*, a black hole 4 million times the mass of the Sun.
What you’re seeing: An artist’s impression informed by Gaia data (ESA/Gaia/DPAC, Stefan Payne-Wardenaar): no one has seen our galaxy from outside.
Magellanic Clouds
Two small galaxies circle the Milky Way, 160,000 and 200,000 light-years away, both visible to the naked eye from the southern hemisphere.
About 60 satellite galaxies.
The Milky Way’s pull is tearing gas out of them: a stream of hydrogen trails behind the Clouds across more than half the sky. Closer in, the Sagittarius Dwarf galaxy is being pulled apart, its stars strewn round the Milky Way in long streams.
What you’re seeing: The galaxies at their measured distances. The gas stream, seen only by radio telescopes, is traced along its measured path. The glow around the Milky Way is its dark matter halo, drawn: it is known only by its pull.
Local Group
The Milky Way, Andromeda and more than 80 smaller galaxies, held together by gravity. Andromeda lies 2.5 million light-years away.
Most of those stars belong to Andromeda and the Milky Way; nearly every other member is a small dwarf galaxy. The two giants are approaching each other at about 110 km/s and may merge in several billion years.
What you’re seeing: Real galaxies at their measured distances. Faint dwarf galaxies are still being discovered.
Nearby galaxy groups
The Local Group is one of several small groups strung along a flat sheet of galaxies.
Over 1,000 galaxies.
In the M81 Group, 12 million light-years away, M81 and M82 are still pulling at each other. Centaurus A, at the heart of its group, is a giant elliptical galaxy that swallowed a spiral and now shoots jets far out into space.
What you’re seeing: Real galaxies at their measured distances. Faint dwarfs are still being found.
Local Supercluster
Galaxies gather around the Virgo Cluster, about 54 million light-years away. The Local Group sits on the outskirts.
About 50,000 galaxies.
The Virgo Cluster alone holds more than a thousand galaxies. Its gravity tugs on the Local Group: we still move away from it as the universe expands, but more slowly than we otherwise would.
What you’re seeing: Real galaxies, placed by their redshift and flattened onto one plane. A strip hidden behind the Milky Way’s disk is missing.
Laniakea
Our home supercluster, about 500 million light-years across. All its galaxies drift toward one region, the Great Attractor.
About 100,000 large galaxies.
Laniakea means “immeasurable heaven” in Hawaiian. It was mapped in 2014 not by where galaxies are but by where they move: its edge is where the flow turns toward another basin. The Great Attractor lies behind the Milky Way’s disk, which long hid it from view.
What you’re seeing: Real galaxies from the 2MASS Redshift Survey, placed by their redshift, over a simulation fitted to the surveyed galaxies, so its filaments and clusters stand where the real ones do. The named clusters stand at their measured places.
Cosmic web
On the largest scales, galaxies gather into filaments and clusters around vast, nearly empty voids.
About a million large galaxies.
Voids can span hundreds of millions of light-years. The web grew from tiny ripples in the early universe, pulled together over billions of years by gravity, mostly that of dark matter.
What you’re seeing: A computer simulation, not a map. Near us it is fitted to the surveyed galaxies, so the big structures are where the real ones are; farther out it shows what the universe looks like on these scales, not where real galaxies are.
Observable universe
Everything whose light has had time to reach us: a sphere about 93 billion light-years across, centered on us.
Hundreds of billions of galaxies.
Looking farther means looking back in time, all the way to the cosmic microwave background, light released 380,000 years after the Big Bang. The sphere is 93, not 27.6, billion light-years across because space kept expanding while the light travelled.
What you’re seeing: An illustration built from a simulation, fading toward the edge, where we see earlier times. The rim is the microwave background as Planck measured it.
Beyond our horizon
Space does not end at our horizon – only our view does. Every place has its own observable universe.
Measurements find space flat within their precision, so the universe may be infinite. If it is finite, it is at least about as large as the part we can see, and it has no edge: like the surface of a globe, it would close on itself.
What you’re seeing: Illustration. The spheres are other places’ observable universes, each as large as ours; their light has not reached us.
Without end
If space has no end, there is no last chapter: past every horizon lie more horizons, without limit.
Perhaps infinitely many galaxies.
An infinite universe would hold infinitely many stars and planets. If matter is spread the same way everywhere, any arrangement of it that can happen must happen again somewhere, this page and its reader included. Max Tegmark estimated that the nearest copy of you would be about 10 to the power of 10²⁹ metres away: a number with more digits than there are stars we can see. No observation could ever reach far enough to check.
What you’re seeing: Other horizons, until they are too small to see; the glow at the edges is imagined, not observed. At this scale our whole observable universe is a speck a few pixels wide.