Understanding the Milky Way
The anatomy of the galaxy we live in — its discs, bulge, bar and spiral arms, the black hole at its heart, how it turns and reveals its dark matter, and how it will one day merge with Andromeda. Built on well-established galactic astronomy; nothing is fabricated.
Related entities
- Galactic structure
The Galactic Centre
The crowded, dust-shrouded core of the Milky Way, about 26,000 light-years away, home to a dense star cluster and the four-million-solar-mass black hole Sagittarius A*. Hidden at optical wavelengths, it is studied in radio, infrared, and X-rays, and its stars' orbits weigh the central black hole directly.
- Galactic dynamics
Galactic Rotation
The Milky Way's disc does not turn as a solid body: inner and outer stars complete their orbits at different rates. Yet the orbital speed stays surprisingly flat far from the centre instead of falling off, one of the clearest signs that the visible Galaxy is embedded in a massive halo of unseen dark matter.
- Galactic dynamics
Stellar Streams
Ribbons of stars strung out across the halo, torn from dwarf galaxies and globular clusters as the Milky Way's tides pull them apart. The great Sagittarius stream wraps entirely around the Galaxy; mapped in their dozens by Gaia, these streams trace the shape of the dark-matter halo and record the Galaxy's past meals.
- Galactic dynamics
The Milky Way–Andromeda Collision
The Milky Way and the Andromeda Galaxy are approaching each other and are predicted to merge into a single elliptical galaxy in roughly four to five billion years, though the exact timing and geometry remain uncertain. Stars will almost never collide, but both discs will be transformed as the two giants of the Local Group become one.