The Death Throes of Stars

When a medium-sized star begins to die, it sheds its outer layers forming a shell of gas and dust called a “planetary nebula,” but the term is misleading. It comes from late eighteenth century astronomers who thought their rounded shape looked similar to the planet Uranus, discovered in 1781. They named them “planetary” nebulas as a result.

collage of Hubble views of planetary nebulas

Hubble has revealed the astounding variety and amazing complexity of planetary nebulas.

NASA

Before the launch of Hubble in 1990, ground-based images suggested that planetary nebulae have simple, spherical shapes. Hubble observations revealed unprecedented details that show they are much more varied and complex. Some planetary nebulae look like pinwheels, others like butterflies, and still others like hourglasses. The extraordinary level of detail offers astronomers insights into the complex dynamics that accompany a star’s release of its outer gaseous layers before it collapses to form a white dwarf or neutron star.

M1, the Crab Nebula, is the remnant of a stellar explosion that was seen in the year 1054 AD. The colors in the image were assigned to distinguish various chemical elements, which are now all racing into space to enrich new generations of stars.

NASA, ESA, J. Hester and A. Loll (Arizona State University)

In 2017, Hubble observed the remnants of an explosion caused by two surviving cores of two massive neutron stars that crashed into each other. The neutron stars collapsed into a black hole that began pulling material toward it. That whirlpool of material formed a rapidly spinning disk that generated blowtorch jets of radiation at nearly the speed of light. Hubble looked at the event just two days after the collision, allowing astronomers to measure the motion of a blob of material propelled by one of the jets slamming into it.

Hubble observations of SN 1987A taken over 22 years show the effects of the stellar explosion’s onrushing stellar shock wave as it slams into, heats up and illuminates the inner regions of the narrow ring surrounding the doomed star.
NASA, ESA, R. Kirshner (Harvard-Smithsonian Center for Astrophysics and Gordon and Betty Moore Foundation), and P. Challis (Harvard-Smithsonian Center for Astrophysics)

Two red rings overlap and bisect a center yellow ring that surrounds a bright-white point of light. As the animation progresses, the rings are viewed from the side revealing how they expanded outward from the central star.

An illustration of how the SN 1987A rings are oriented toward Earth.

NASA, STScI

Learn More

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$A string of pinkish pearls surrounds an exploded star. Black background dotted with stars. Two bright stars, with diffraction spikes, at lower left and upper right of the ring.$
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