‘Necklace Nebula’ formed by drowning star
Two stars, bound together in orbital matrimony, are slowly ripping each other apart, and like many relationship squabbles, this stellar spat ends with jewellery.
Meet the Necklace Nebula, also known as PN G054.203.4. This planetary nebula is located about 15,000 light years from Earth, inside the Sagitta constellation. To telescopes like Hubble, the nebula looks like an emerald oval ringed with sparkling clusters of jewel-like gas. A binary star forms a bright speck at the centre.
That speck looks like a single star, but it’s no bachelor; about 10,000 years ago, the star grew so large that its outermost layer of gas actually swallowed up a smaller companion star. That smaller companion star is still orbiting inside its larger partner’s gassy sheath, known as a common envelope. As the smaller star orbits through its larger partner, the gas surrounding the duo begins to rotate faster and faster. At some point the gas surrounding this stellar couple started swirling so fast that huge swaths of it started spilling out into space.
That runaway gas escaped in an oval shape, gushing outwards for trillions of miles in every direction, thus creating the necklace shape. As for the sparkling jewels running along the outside of the ring? These are areas where the stellar gas bunched up into dense clusters.
For now the two stars at the centre of the nebula will continue their mad ballroom dance around each other, completing a full orbit in a little more than an Earth day. But their end is uncertain. Many binary couples end their relationships with immense supernova explosions. BRANDON SPECKTOR