W3 is a giant star-forming complex in Cassiopeia, a radio-bright nest of newborn massive stars in the Perseus Arm, beside the Heart and Soul nebulae.
At a glance
| type | nebula |
|---|---|
| distance from the Sun | 6,110 light-years (1.87 kpc) |
| its light left it | 6,110 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 W3
W3 takes its letter from Gart Westerhout’s radio catalogue of the Milky Way’s brightest sources. It is a giant molecular cloud in the Perseus Arm, the next spiral arm outward from the Sun, and part of a larger complex with the Heart Nebula, W4, and the Soul Nebula, W5, whose hot clusters have carved huge cavities in the gas.
Along the dense edge facing W4, W3 is forming massive stars. Radio and infrared telescopes see ultracompact pockets of ionised hydrogen around stars still in their natal cocoons, and powerful masers. Radio interferometers measured the parallax of the maser source W3(OH) directly, one of the first trigonometric distances to a spiral arm beyond our own, and it settled where the Perseus Arm lies.
What you see in the piece
In the piece it is a broad cloud of glowing gas in the Perseus Arm, beyond the Orion Spur. Dust in front of it dims it from the Sun; the radio band shows it best.
Questions
How was the distance to W3 measured?
Radio interferometers measured the parallax of masers in W3(OH), giving a direct geometric distance to the Perseus Arm. On the card it is 6,110 light-years (1.87 kpc) from the Sun.