Posted on by Evan Gough

Each Planetary Nebula is Unique. Why Do They Look So Different?

A large collage of planetary nebulas processed by Judy Schmidt. All are presented north up and at apparent size relative to one another. Colors are aesthetic choices, especially since most planetary nebulas are imaged with narrowband filters. Image Credits: NASA / ESA / Judy Schmidt

When it comes to cosmic eye candy, planetary nebulae are at the top of the candy bowl. Like fingerprints—or maybe fireworks displays—each one is different. What factors are at work to make them so unique from one another?

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Posted on by Evan Gough

A Second Generation of Planets can Form Around a Dying Star

An illustration of a protoplanetary disk. The solar system formed from such a disk. Astronomers suggest this birthplace was protected by a larger filament of molecular gas and dust early in history. Credit: NASA/JPL-Caltech/T. Pyle (SSC)
An illustration of a protoplanetary disk. The solar system formed from such a disk. Astronomers suggest this birthplace was protected by a larger filament of molecular gas and dust early in history. Credit: NASA/JPL-Caltech/T. Pyle (SSC)

When young stars coalesce out of a cloud of molecular hydrogen, a disk of leftover material called a protoplanetary disk surrounds them. This disk is where planets form, and astronomers are getting better at peering into those veiled environments and watching embryonic worlds take shape. But young stars aren’t the only stars with disks of raw material rotating around them.

Some old, dying stars also have disks. Can a second generation of planets form under those conditions?

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