William Herschel coined the term “planetary nebula” for those cloudy objects found in 18th century telescopes that resembled planets. These nebulae (from the Latin for “cloud”) were in fact shells of gas and dust blown from stars near the end of their life cycle. Someday, maybe in three to five billion years, the sun will belch much of its contents and old Earth will be near the center of a planetary nebula.
Some planetary nebula appear as more or less regular spheres. Irregularly shaped nebula outnumber them about four to one, however. The reasons for irregularity aren’t completely understood. Here’s the Calabash Nebula, decidedly non-spherical:
Irregular nebulae may be formed, it is thought, by the outgassing stellar material interacting with a companion star or with magnetic fields. Scientists think that a small “obstacle” put in the path early might result in a significant defect in the theoretically round shape one might expect from a star blowing off material more evenly.
Astronomers at my alma mater think they might be on to something else. Eric Blackman, professor of physics and astronomy from the Astrophysical Journal Letters:
Few researchers have explored how something as small as a very low-mass star, or even a massive planet can produce several flavors of nebulae and even change the chemical composition of dust around these evolved stars.
This is an intriguing notion on a few fronts.
For scientists ready to dismiss planets as minor players in the universe, we have only to consider the effect Enceladus has on giant Saturn. The tiny moon, one six-millionth the mass of the planet, puts a noticeable drag on the Saturnian magnetosphere–enough of a drag to disconnect it from the planet’s internal rotation. Just for reference the mass ratio of our sun and the Earth is 318,000 to 1.
A late life outgassing would not destroy a planet of any size. But it would be strong enough to rip away a lot of atmosphere. Irregularities and impurities might be evidence of gas giants in the neighborhood. We know that planets and moons are sources of complex chemicals. Some of these chemicals might survive a violent separation from their planet and end up in the deep reaches of interstellar space. The Calabash Nebula above, is also known as the Rotten Egg Nebula because scientists have discovered a lot of sulfur in that cloud.
Before getting excited about planets, we should remember that stars are very complex and violent places. We know very little about late-stage stars, and it seems more likely that gigantic processes within them contribute the most to the planetary nebulae they form.
I guess we’ll just have to get out there someday and see for ourselves.