spaceSpace and Physics

Best View Yet Of A Stellar Ghost


Stephen Luntz

Stephen has a science degree with a major in physics, an arts degree with majors in English Literature and History and Philosophy of Science and a Graduate Diploma in Science Communication.

Freelance Writer

1598 Best View Yet Of A Stellar Ghost
The Southern Owl Nebula, 3,500 light-years away, seen with unprecedented clarity. Credit ESO

The European Southern Observatory (ESO) has released the image above (and video below) of the planetary nebula known as the Southern Owl Nebula. The ghostly beauty is produced by a medium-sized star in a brief stage near the end of its lifecycle.

Stars with mass greater than eight times the Sun die spectacularly as core collapse supernovae. Stars substantially lighter than the Sun live for so long that even the first generation to form are still in the steady burning stage of their lives. Stars with masses in between, possibly the Sun included, will eventually become red giants. Red giant stars emit stellar winds far more powerful than the Sun's solar wind.


Where the Sun blows off just one-trillionth of a percent of its mass each year, red giants lose their entire outer atmosphere as an expanding bubble of gas. The loss of the star's atmosphere exposes an ultraviolet-emitting core around 30,000 °K. The high-energy light from the core ionizes the gas bubble to create the glowing shells we see.

The name, by the way, is misleading, since planetary nebulae have nothing to do with planets. However, William Herschel didn't know that when he chose the name.

These beautiful bubbles can grow to enormous size. PLN 283+25.1, or K1-22 as the Southern Owl Nebula is technically known, is two light-years across, half the distance from the Sun to Alpha Centauri.

Although a great many stars will go through a planetary nebula stage, these beautiful objects are rare because the period is so short by astronomical standards, lasting just a few thousand years in the multi-billion year lifespans of the stars that produce them. After this, the gas bubbles get too far away from the star to remain illuminated. The remnant star burns on for a billion years or so before collapsing to become a slowly cooling white dwarf.


“The lifetime of a planetary nebula as a fraction of a star's life is about the same as the life of a soap bubble compared to the age of the child who blows it,” the ESO notes.

Planetary nebulae represent a way in which the heavier elements produced within stars can be dispersed through the galaxy, eventually becoming a new generation of stars and planets.

The Southern Owl Nebula gets its name from its resemblance to M97, also known as the Owl Nebula. It is much less well known than its Northern counterpart, and at 3,500 light-years away, it is almost twice the distance. It has never before been photographed in such detail.

The image has been released as part of the ESO Cosmic Gems program in which downtime on the telescopes that cannot be used for ordinary scientific purposes is devoted to taking beautiful images to generate enthusiasm for astronomy.





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