California Nebula
What is California Nebula?
Nebulae· Distance 1,000 ly. A nebula stretched across Perseus like a map of California, lit by the passing runaway star Xi Persei. Only 1,000 light-years away, it also appears in the Nearby Stars 3D view.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where California Nebula is in your sky right now: https://nowsky.org/solar/sky?sel=california nebula — location and time set automatically, no login.
Its place in the sky
A nebula, in the direction of Perseus, spanning about 145 arcminutes of sky — 4.7 times the width of the full Moon.
Distance and scale
| Distance | ~1,000 ly |
|---|---|
| Size | ~100 ly long (5 full Moons) |
| Type | emission nebula |
| Constellation | Perseus |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Discovery and name
Found by Barnard in 1884, named for its shape — and it passes overhead in California.
Frequently asked
- How far is California Nebula from Earth?
- ~1,000 ly.
- What kind of object is California Nebula?
- emission nebula.
- Where in the sky is California Nebula?
- In the direction of Perseus.
- Where is California Nebula in the sky right now?
- Open the sky view for your location and time and it shows the position in the sky right now.
Red in photographs, absent to the eye — the hydrogen-alpha problem
The California Nebula is large and red in photographs but nearly invisible in a telescope. The reason is colour. Most of its light is the red hydrogen line at 656 nm (H-alpha), and in the dark the human eye barely responds at that wavelength — night vision peaks in the blue-green around 500 nm. A camera collects the red light in full, which is why picture and eye diverge so far.
To see the nebula by eye one uses a filter passing not H-alpha but hydrogen-beta (486 nm), or the green oxygen line that lights the Orion Nebula. Even then the California is a faint smudge in a large telescope under dark skies with an H-beta filter. That the red of emission-nebula photographs cannot be seen by eye is the commonest demonstration that astronomical images are records of light, not views.
The nebula in depth
The California Nebula (NGC 1499) is an emission nebula about 1,000 light-years away in Perseus. Some 100 light-years long, it spans 2.5° of sky — five full Moons — and its elongated outline resembles the state of California. American astronomer Edward Barnard discovered it in 1884.
The nebula is lit by Xi Persei (Menkib), a 4th-magnitude star to its south. This O-type star of about 40 solar masses is a runaway ejected from the Perseus OB2 association, cruising past the cloud at tens of kilometers per second and ionizing its hydrogen with ultraviolet light. The glow is a chance encounter between star and interstellar cloud; once the star moves on, the nebula will fade again.
In the Sky view, look between Perseus and the Pleiades in Taurus on autumn and winter evenings, just north of the star Menkib. Its surface brightness is so low that eyes and binoculars barely register it; only a wide-field telescope with a hydrogen-beta filter or a long-exposure photograph shows the red band. Compare it with the solar system on the size ladder to feel how long 100 light-years really is.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.