Look at almost any picture of deep space and you will see them: vast clouds of red, pink, blue and violet, glowing against the black, shot through with stars. They look like something a painter invented. They are real, they are enormous, and they are some of the most important objects in the universe.
The simple answer
A nebula is a cloud of gas and dust in space. The word is Latin for cloud or mist. Before telescopes were good enough to tell the difference, astronomers used it for any fuzzy patch of light in the night sky.
The gas is mostly hydrogen, the simplest and most common element, with some helium and traces of others. The dust is made of tiny solid grains. Together they form clouds that can stretch across many light years. A light year is the distance light travels in a year, about six trillion miles.
For all their size, nebulae are extremely thin. The gas in them is far emptier than the best vacuum that can be made in a laboratory on Earth. They are visible only because there is so much of them.
Where stars are born
Some nebulae are stellar nurseries. Inside a large, cold cloud, gravity slowly pulls gas and dust into clumps. A clump grows denser and hotter as more material falls in. When the centre becomes hot and dense enough, nuclear fusion begins, and a star switches on.
Our own Sun formed this way, from a cloud of gas and dust, about four and a half billion years ago. The leftover material around it became the planets, including this one.
Where stars end
Other nebulae are what is left when a star dies.
- A star like the Sun, at the end of its life, puffs its outer layers off into space. They form a glowing shell around the hot core that remains. These are called planetary nebulae. The name is a historical accident: through early telescopes they looked like round, planet-like discs. They have nothing to do with planets.
- A much larger star ends in an explosion called a supernova, which throws its material outward at great speed. The expanding wreckage is a supernova remnant.
The material thrown out by dying stars drifts into space and, in time, becomes part of new clouds. From those, new stars form. The heavier elements in your body, the carbon, the oxygen, the iron in your blood, were made inside stars that died long before the Sun existed.
Why they glow
- Emission nebulae shine with their own light. Hot young stars nearby pour out energy that excites the gas and makes it glow, in a similar way to the gas in a neon sign. Hydrogen glows red, which is why so many nebulae are pink and crimson.
- Reflection nebulae don't glow themselves. Their dust scatters the light of nearby stars. Blue light scatters most easily, so these appear blue. It is the same reason the sky is blue.
- Dark nebulae are clouds dense enough to block the light from whatever is behind them. They show up as black shapes against a brighter background.
A single region of space can contain all three: red glowing gas, blue reflected light and dark lanes of dust across it. That is where the rich, layered look comes from.
Are the colours real?
Partly. If you looked at a nebula through a telescope with your own eye, you would see a faint greyish smudge. The human eye is poor at colour in dim light.
Cameras do better. A long exposure collects light for minutes or hours and reveals the colour that is really there: the red of hydrogen, the blue of scattered starlight.
Many famous space images go further. Telescopes record light through separate filters, sometimes including kinds of light we can't see, such as infrared. Scientists then assign a visible colour to each one and combine them. The result shows true structure, with colours chosen to make it readable. So the shapes are real, and the colours are a translation.
Why nebulae suit a wall
- They are abstract and real at once. A nebula has no outline, no horizon and no right way up. It works as pure colour and form. It is also a picture of a real place.
- The colours are rich. Reds, magentas, violets and blues on black. They look expensive.
- They have depth. Layers of cloud and stars at different distances make a wall feel deeper.
- They are calm. There is no action and no face. The eye wanders.
- They mean something. A picture of where stars and planets come from is a good thing to look at.
Light Nebula
Light Nebula shows a great sweep of cloud across a black, star-filled sky. Deep red and pink on the left curl into violet and blue on the right, with a bright core where the colours meet. It has both of the classic nebula colours, the red of glowing gas and the blue of scattered light, in one frame.
It comes as a poster, a framed poster, a pin and a keychain.
How to hang nebula art
- On a dark wall, it glows. On a white wall, it is a dramatic dark window.
- Use a black frame, to continue the darkness at its edges.
- Go large if you can. Clouds need room.
- Choose matte. A glossy cover over black reflects the room. See matte vs glossy prints.
- Light it. Dark art disappears in a dim corner.
- Pair it with an astronaut for scale, or a black hole for contrast. See astronauts in art and Black Hole.
Good rooms for it
Bedrooms, studies, reading corners, and any room with purple or blue in it. For someone who loves astronomy, a framed nebula is a thoughtful gift. Browse the poster prints and canvas art collections for more space pieces.