Such cosmic resurrections are a rare sight, astronomers say

Jul 28, 2015 14:22 GMT  ·  By

The Abell 78 planetary nebula was discovered by George Abell in 1966. It sits in the constellation of Cygnus, and like all other planetary nebulae, it is essentially the corpse of a star that, having reached the end of its life, ejected its outer layers into space. 

Except that, unlike most other stars, the one that formed Abell 78 did not simply wither and die.

On the contrary, a view of this eye-shaped planetary nebula obtained by astronomers with the help of the European Space Agency's XMM-Newton space observatory and the Nordic Optical Telescope in the Canary Islands tells the tale of a cosmic resurrection.

The view, available below, shows signs of nuclear activity. Fusion of helium, to be more precise.

While planetary nebulae are a fairly common sight, such events are extremely rare. So much so that, even with all the telescopes and space observatories they have at their disposal, scientists have so far only managed to documented a handful of such reborn stars.

“Only a handful of such born-again stars have been discovered,” astronomers say.

Well then, how did this resurrection happen?

Before you ask, no, there were no aliens around that took pity on the dying star at the core of Abell 78 and gave it CPR. The nebula came back to life all on its own, and it did a pretty good job of it.

As explained by scientists, most stars whose size is comparable to that of our Sun eventually exhaust the nuclear fuel in their entrails. When this happens, they eject their outer shells and collapse onto themselves, becoming dense and insanely hot white dwarfs.

In turn, the material spewed out by these dying stars gets entangled with the cosmic gas and the dust surrounding the orbs, creating the odd-shaped clouds astronomers call planetary nebulae.

In the case of Abell 78, the outer layers ejected by the star got so dense that nuclear activity resumed. All this commotion left its imprint on the nebula's appearance. Thus, it created the bright filaments that scientists' instruments detected stemming from the dying star.

“Some of the star’s outer layers became so dense that fusion of helium resumed there. The renewed nuclear activity triggered another, much faster wind, blowing more material away.”

“The interplay between old and new outflows has shaped the cloud’s complex structure, including the radial filaments that can be seen streaming from the collapsing star at the center,” scientists say.

Our Solar System might have the same fate

The dying star that birthed the Abell 78 planetary nebula is believed to have had a mass comparable to that of the Sun. Hence, astronomers cannot help but wonder whether, as our parent star ages, our good old cosmic neighborhood might not too became such a bizarrely shaped cloud of gas and dust.

Since the Sun is about 4.6 billion years old and has so far burned through about half its fuel reserves, this means this riddle will soon enough solve itself. Let's just hope we'll still be around by then to see how things work out.

Planetary nebula Abell 78
Planetary nebula Abell 78

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All stars are eventually left without fuel and die
Planetary nebula Abell 78
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