The Double Cluster is a pair of young open clusters in Perseus, rich in hot blue supergiants and visible to the naked eye as a brighter knot in the Milky Way.
At a glance
| type | open star cluster |
|---|---|
| distance from the Sun | 7,500 light-years (2.3 kpc) |
| its light left it | 7,500 years ago |
| size in the piece | about 100 light-years acrossmodel |
Read off the piece’s own catalogue, the same values it draws with. Model marks a property of the piece’s galaxy model rather than a measurement.
About Double Cluster
The two clusters, NGC 869 and NGC 884, known as h and Chi Persei, sit side by side on the sky and lie at similar distances, in the Perseus Arm, the next spiral arm out from the Sun. Both are young, and they are thought to have formed in the same episode of star birth, part of a wider association of massive stars in the same region.
Their brightest members are blue and white supergiants, massive stars only a short time into their lives, with a few red supergiants among them, stars of the same generation that have already exhausted the hydrogen in their cores. Because so many stars of known age sit together at one distance, the pair is used to test how massive stars evolve.
Known since antiquity as a hazy patch, it was left out of Messier’s catalogue despite being one of the finest sights for binoculars in the northern sky.
What you see in the piece
From the Sun the two clusters sit close together and dim with their distance; fly to them and they separate into two crowds of blue-white stars, with the occasional orange-red supergiant among them.
Measured or modelled
The extent drawn for the pair is modelled. Whether the two clusters are physically bound to each other is not established.
Questions
How far away is the Double Cluster?
The Double Cluster is about 7,500 light-years (2.3 kpc) from the Sun, in the Perseus Arm of the Milky Way.
Can you see the Double Cluster without a telescope?
Yes, from a dark site it shows as a small hazy patch between Perseus and Cassiopeia, and binoculars split it into two rich clusters.