The Milky Way is the name given to the bright band that stretches across the night sky. What we see is actually our own galaxy viewed from within, from our position in one of its spiral arms. This band contains hundreds of billions of stars whose collective light creates this characteristic whitish streak. Yet, most people have never seen the Milky Way with their own eyes. Why does this celestial wonder so often elude us?
To understand why the Milky Way changes appearance throughout the year, we must consider three fundamental axes that determine what we see in the night sky.
The Milky Way is a flat spiral galaxy, like a disk. This disk of stars defines what is called the galactic plane. The galactic axis is the perpendicular line passing through the center of this disk.
We are inside this disk, in one of its spiral arms, about 26,000 light-years from the center. When we look along the plane of the disk, we see the milky band of the Milky Way. When we look perpendicular to the disk (along the galactic axis), we see far fewer stars.
This galactic axis has a fixed orientation in space. The center of the galaxy is located in the constellation Sagittarius, about 29° below the celestial equator.
The ecliptic is the plane of Earth's orbit around the Sun. Its axis is perpendicular to this orbital plane.
The galactic plane and the ecliptic plane are not aligned. They are tilted relative to each other by about 60°.
Earth rotates on its axis every 24 hours, which passes through the North and South geographic poles. This axis is tilted by about 23.5° relative to the ecliptic axis, which explains the seasons.
This rotational axis determines what is visible above your local horizon at any given time: Earth's rotation makes the night sky "turn" above you, from east to west, in one night.
During a single night: Earth's rotational axis makes the sky turn. The galactic plane, fixed in space, thus appears to "pivot" above you. At the beginning of the night, the Milky Way may be horizontal near the horizon, then become vertical around midnight, and descend back toward the horizon at dawn.
Throughout the year: Earth moves along the ecliptic around the Sun. At night, we look in the direction opposite the Sun. Since the galactic plane is tilted 60° relative to the ecliptic plane:
Northern Hemisphere: The best nights to see the galactic center are from April to September, peaking in July-August. During these summer months, Sagittarius (where the center is located) is visible in the night sky, especially between 11 PM and 4 AM.
Southern Hemisphere: The galactic center is visible for much of the year, but the best conditions are between February and October. In the southern winter (June-August), the galactic center passes overhead at midnight, offering spectacular views.
| Latitude | Hemisphere | Milky Way Visibility | Appearance at 00:00 | Appearance at 04:00 | Maximum Altitude of the Galactic Center | Comment |
|---|---|---|---|---|---|---|
| 0° | Equator | Excellent | Vertical ~90° | Inclined ~60° | ~61° | The galactic plane passes high in the sky, almost at the zenith |
| +15° | North | Very Good | Very vertical ~80° | Inclined ~50° | ~46° | The galactic center is clear but not dominant |
| -15° | South | Excellent | Very vertical ~85° | Inclined ~55° | ~76° | The galactic core approaches the zenith |
| +30° | North | Very Good | Vertical to inclined ~70° | Inclined to lying ~40° | ~31° | Center still low, moderate visibility |
| -30° | South | Exceptional | Very vertical ~90° | Inclined ~70° | ~89° | The central bulge almost at the zenith |
| +45° | North | Good | Inclined ~60° | Lying ~30° | ~16° | Center very low, reduced visibility |
| -45° | South | Excellent | Vertical ~80° | Inclined ~50° | ~61° | Center high and contrasted |
| +60° | North | Average | Inclined ~45° | Lying ~20° | ~1° | Galactic center almost at the horizon |
| -60° | South | Very Good | Vertical ~75° | Inclined ~55° | ~59° | Excellent exposure to the central bulge |
| +75° | North | Poor | Lying ~10° | Lying ~5° | ~0° | The center remains below or on the horizon |
| -75° | South | Good | Inclined ~40° | Lying ~15° | ~44° | Still good access to the heart of the galaxy |
| +90° | North Pole | Very Poor or Impossible | Lying ~0° | Lying ~0° | ~-29° | Galactic center below the horizon, invisible |
| -90° | South Pole | Poor | Lying ~10° | Lying ~5° | ~13° | Galactic center low but partially observable |
Why Is It So Hard to See the Milky Way? 
What Is a Galaxy? Journey to the Land of Billions of Stars 
Galaxies from the Depths: Light from the Primordial Universe 
Journey to the Heart of the Milky Way: Mysteries and Wonders 
JWST and Protogalaxies: Exploring the First Cosmic Structures 
Collision and Cannibalism: How Large Galaxies Absorb Smaller Ones 
Beyond Our Senses! 
Future Collision of Our Galaxy with the Sagittarius Galaxy 
Differences between the Milky Way and the Andromeda Galaxy 
Why are Galaxies, Unlike Stars, So Close to Each Other? 
Galaxies of the Local Group 
The hidden galaxy, one of Euclid's first images 
The Virgo Cluster spans approximately three Full Moons 
Where did the dark matter in our Galaxy go? 
Galaxy Mergers: From Encounter to Coalescence 
Gravitational Lenses: When Spacetime Bends Light 
Cartwheel Galaxy: A Wheel of Fire in the Universe 
From Dust to Stars: The Composition of Galaxies 
Galaxy Merger NGC 6745: A Traversal of One by the Other 
The mystery of gamma bursts 
The Cigar Explosion 
Extreme Shock Waves in the Universe: Impact on the Evolution of Cosmic Structures 
Gould's belt, a stellar fireworks display 
Zoom on Our Galaxy: Journey to the Center of the Milky Way 
One Galaxy, Two Hearts: The Mystery of Andromeda's Double Nucleus 
The most beautiful galaxy clusters 
Tinker Bell's Gravitational Flight: A Merger of Three Galaxies 
Coma or Berenice’s Hair: The Cosmic Colossus 
When Dark Matter Reveals Itself 
El Gordo galaxy cluster 
Einstein ring and cross 
How to measure distances in the Universe? 
The Cigar Galaxy: A Smoke of Stars in the Night 
The Hubble Sequence: The Secret Code of Galactic Shapes 
Dance of the Stars: The Arms of the Milky Way 
The most beautiful galaxies 
Ancient Galaxies and Cosmic Evolution: A Deep Look Back in Time 
Quasars: Beacons of the Distant Cosmos 
Sagittarius A black hole at the center of our Galaxy 
MOND Theory and Dark Matter: Why MOND Fails in Cluster Collisions 
Central area of the Milky Way 
Laniakea, our supercluster of galaxies 
The Antennae Galaxies: An Ongoing Cosmic Collision 
NGC 1275: A Turbulent Galaxy in the Perseus Cluster 
NGC 1672: A Barred Spiral Galaxy in Full Activity