Floating, seemingly serenely, in the vastness of interstellar space are numerous ethereal clouds of gas and dust, the unearthly remains of dead and dying stars and the raw materials from which a new generation of stars and planets will be born. But don’t be fooled – their apparent beauty and tranquillity belies their violent origins.
Given the variety of strange celestial objects, perhaps it was inevitable that astronomers would spot one that looks like a bird – at least, from this angle. Rather than flying toward the top right, the gas in this small nebula, known as vdb 141se, is being swept away to the lower left by the light and wind of stars out of frame at top right.
The Elephant’s Trunk Nebula, located 2,400 light-years from Earth, is a thick cloud of gas and dust with a glowing edge. That glow is produced by the radiation and wind from a hot star (out of the field of view at the top) that is ionising and compressing the gas. Dense regions of raw material in the trunk itself are places where many infant stars in the process of forming.
When stars similar to the Sun reach the end stage of their lives, they slough off their outer gas layers in an expanding shell, uncovering the hot core beneath. Intense ultraviolet light from the core ionises the gas (changes atoms and molecules to charged particles), making it glow. Astronomers call them planetary nebulae, because of their superficial resemblance to planets when seen through small telescopes. This one is the Dumbbell Nebula, about 1,200 light-years from Earth.
Looking like a giant jellyfish swimming through space, planetary nebula HFG1 surrounds a binary star system. The system is moving quite rapidly through space towards the upper-right, ploughing through the thin gas that exists in interstellar space and forming a blue bow-shock on the nebula’s leading edge.
Looking like something out of 1984 movie Ghostbusters, CG4 is a ‘cometary globule’ nebula about 1,300 light-years from Earth. While it appears to be moving to the left, as if to devour the galaxy seen edge-on there, CG4’s gas is being blown to the right by pressure from bright stars just off the left edge of the image.
A lonely planetary nebula, Jones 1, glows faintly against a starry backdrop in the Northern Hemisphere sky. The large shell of gas was expelled in the distant past by a hot star (the middle one of the three stars in vertical row) at the centre of the nebula. This is a false-colour image – filters were used to pick out emission from ionised oxygen gas (given a blue colour) and hydrogen (orange).
Sitting atop a cloud of thick, dark interstellar dust (a patch known as Barnard 175) is a bright nebula, vdb 152, lit up from within by the light of an embedded star. The star was not originally part of the nebula; it just happened to cross paths with it. At upper right are unrelated, thin, red filaments of gas – the remains of a supernova explosion. This region of gaseous turmoil, like many others, is the raw material from which a new generation of stars will be born. Indeed, the small, red blob near the top of the nebula marks the site of a newly formed star.
Known as the Iris Nebula – named after the flower for its shape and colour – this is a reflection nebula, meaning it gets its luminosity from starlight reflected off dust grains the nebula contains. (This distinguishes it from red/pink emission nebulae, which glow because they’ve been energised by starlight interacting with the gas.) In this case, the light is coming from a huge, hot star in the centre of the cloud. The Iris Nebula is about 1,300 light-years from Earth.
Located 11,000 light-years from Earth, the Bubble Nebula is a huge cavity carved into a gas cloud by the fast wind emitted by a massive, hot, young star. Background nebulosity, too, is lit up with light from the star, while simultaneously acting as a physical barrier to the cavity’s growth.
Glowing faintly in the reflected ambient light of the Milky Way, the perfectly spiral-shaped pre-planetary nebula known as IRAS 23166+1655, was produced by two stars (hidden behind the dusty cloud in the spiral’s centre) spinning around each other, locked in an orbital embrace. One of the stars is losing gas, which the pair’s combined orbital spin has sent curling outwards like water from a sprinkler.