The Tulip Nebula (Sh2-101) lies in Cygnus, about 6,000 light years away, and owes its name to the goblet shape it takes on in long exposures. It is a region of ionised hydrogen, lit by the star HDE 227018.
But the most remarkable thing in this field is not the flower: not far away sits Cygnus X-1, the first object accepted as a black hole. It is a binary system in which a blue supergiant loses matter to an invisible companion of some twenty solar masses; the gas falling in heats to millions of degrees and shines in X-rays — which is how it was discovered, in 1964, by a sounding rocket.
The jet emitted by Cygnus X-1 carves an arc into the interstellar gas, visible in H-alpha at the bottom of the field: the only sign, in ordinary light, of what is going on in there.
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