Physics & Astronomy

Finally, the ‘Planet’ in Planetary Nebulae

New research by Rochester scientists indicates that a description long thought inaccurate is right after all.

Jonathan Sherwood ’04 (MA)

When astronomers discovered “planetary” nebulae 300 years ago, they weren’t sure what they were seeing and so named the objects for their resemblance to the planet Uranus. But as early as the middle of the 19th century, astronomers realized that while the nebulae might look like planets, they’re really great clouds of dust emitted by dying stars.

NEBULOUS NAME? Of the 200 billion stars in our own galaxy, only about 1,500—such as the Ant Nebula—have been identified in the planetary nebula stage (photo: NASA).

Now astronomers at Rochester—home to one of the world’s largest groups of specialists in planetary nebulae—have announced that the name “planetary nebulae” might not be a misnomer after all. Low-mass stars and possibly even super-Jupiter-sized planets may be responsible for creating some of the most breathtaking objects in the sky.

“Few researchers have explored how something as small as a very low-mass star, a brown dwarf, or even a massive planet can produce several flavors of nebulae and even change the chemical composition of dust around these evolved stars,” says Eric Blackman, professor of physics and astronomy. “If the companions can be this small, it’s important because low-mass stars and high-mass planets are likely quite common and could go a long way toward explaining the many dusty shapes we see surrounding these evolved stars.”

Blackman anchored the research team that has studied the consequences of a dying star that possesses an orbiting companion. The team has recently published its findings in Astrophysical Journal Letters and Monthly Notices of the Royal Astronomical Society. NASA and the National Science Foundation funded the research.

As a star begins to deplete its fuel near the end of its life, its core contracts and its envelope expands, eventually throwing off its outermost layers millions of miles into space. One time in five, says Blackman, this envelope keeps its roughly spherical shape as it expands. Much more often, however, this envelope contorts and elongates into new and fantastic shapes.