NASA and the European Space Agency (ESA) have released a new image from the Hubble Space Telescope of the Twin Jet Nebula, also known as PN M2-9.
The M in this name refers to Rudolph Minkowski, a German-American astronomer who discovered the nebula in 1947. The PN, meanwhile, refers to the fact that M2-9 is a planetary nebula. The glowing and expanding shells of gas clearly visible in this image represent the final stages of life for an old star of low to intermediate mass. The star has not only ejected its outer layers, but the exposed remnant core is now illuminating these layers — resulting in a spectacular light show. However, the Twin Jet Nebula is not just any planetary nebula, it is a bipolar nebula.
Ordinary planetary nebulae have one star at their center, bipolar nebulae have two, in a binary star system.
The two stars in this pair each have around the same mass as the Sun, ranging from 0.6 to 1.0 solar masses for the smaller star, and from 1.0 to 1.4 solar masses for its larger companion.
The larger star is approaching the end of its days and has already ejected its outer layers of gas into space, whereas its partner is further evolved, and is a small white dwarf.
The characteristic shape of the wings of the Twin Jet Nebula is most likely caused by the motion of the two central stars around each other. It is believed that as the dying star and white dwarf orbit around their common center of mass, the ejected gas from the dying star is pulled into two lobes rather than expanding as a uniform sphere. However, astronomers are still debating whether all bipolar nebulae are created by binary stars. Meanwhile the nebula’s wings are still growing and, by measuring their expansion, astronomers have calculated that the nebula was created only 1,200 years ago.
Bill Condie is a science journalist based in Adelaide, Australia.
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