Bubble Nebula
What is Bubble Nebula?
Nebulae· Distance 7,100 ly. A soap bubble seven light-years wide, blown by the 1,700 km/s wind of a star 45 times the Sun's mass. The star sits off-center, so one side of the bubble glows thicker. Next to Cassiopeia's W, it never sets from Korea.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where Bubble Nebula is in your sky right now: https://nowsky.org/solar/sky?sel=bubble nebula — location and time set automatically, no login.
Its place in the sky
A nebula, in the direction of Cepheus, spanning about 15 arcminutes of sky — 0.5 times the width of the full Moon.
Distance and scale
| Distance | ~7,100 ly |
|---|---|
| Size | ~7 ly bubble |
| Type | emission nebula (wind-blown bubble) |
| Constellation | Cassiopeia |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Discovery and name
Found by Herschel in 1787 — a 7-ly soap bubble blown by the wind of a 45-solar-mass star.
Frequently asked
- How far is Bubble Nebula from Earth?
- ~7,100 ly.
- What kind of object is Bubble Nebula?
- emission nebula (wind-blown bubble).
- Where in the sky is Bubble Nebula?
- In the direction of Cepheus.
- Where is Bubble 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.
The Hubble 26th-anniversary image — knots and fronts inside the bubble
In 2016, to mark its 26th anniversary, Hubble photographed the whole Bubble Nebula as a mosaic. Until then it had captured only parts of the bubble, and this image was the first to hold the 7-light-year sphere in one frame. It shows variations in the thickness of the bubble's wall, the bright front where the star's ultraviolet light burns into the surrounding molecular cloud, and the dense knots of dust left behind it.
The image also explains why the star sits off-centre: the gas around it is uneven in density, and the stellar wind has pushed farther on the thinner side. The wall is still expanding at a few kilometres a second, and when the star goes supernova the bubble will be the first wall its shock strikes. The star is about four million years old, and what remains of its life is shorter than that.
The nebula in depth
The Bubble Nebula (NGC 7635) is an emission nebula about 7,100 light-years away in Cassiopeia. An almost perfect sphere seven light-years wide floats inside a larger molecular cloud; William Herschel discovered it in 1787. It became widely known in 2016 when Hubble chose it for its 26th-anniversary image.
The bubble is blown by SAO 20575 (BD+60 2522), a hot O-type star of about 45 solar masses. Its wind pushes the surrounding gas outward at 1,700 km/s, inflating the bubble, while the cold molecular cloud outside confines it. The star sits off-center because the gas on one side is denser and slows the expansion there. The bubble is still growing at over 100 km/s.
In the Sky view, look a little southwest of Caph, the western end of Cassiopeia's W, near the open cluster M52. As a circumpolar object it never sets from Korea and passes near the zenith on autumn evenings. The nebula itself is faint — a telescope of 20 cm or more with a filter shows the rim of the bubble — but even modest photographic gear captures it well.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.