Look, I’ve been around the block a few times. I’ve spent my whole life as an astronomer, so I’ve seen pretty much every big, bright object there is in the sky.
However, “pretty much” != “all”. It’s still possible to surprise me, and folks, let me tell you: the Gemini telescope’s observation of the nebula Kronberger 61 did just that!
Wow! [Click to ennebulenate.] It looks like a buckeyball or a soccerball; my wife pointed out it looks like the shape you get when you use a bubble maker to make a bunch of bubbles all stuck together. Kn 61, as it’s called, is actually a planetary nebula, the gas flung off by a star like the Sun as it dies. You can get the details (along with many pretty pix) of how this works in a recent post of mine. In a nutshell, when a star runs out of useable hydrogen fuel in its core, it expands into a red giant and expels a huge wind of gas. This strips away the outer layers of the star, revealing the hot, dense core. Ultraviolet light from that star then lights up the surrounding gas, making these gorgeous nebulae.
The exact mechanisms for this process, however, are still not clear. I studied planetary nebulae (so-called because they sometimes resemble planetary disks through small telescopes) when I was in grad school, and a big question then was how the creation of these things depends on whether the central star was solitary, like the Sun, or had a companion (or planets). This relationship is still not clear, in fact, which is where Kn 16 comes in.
This nebula happens to be in the field of view of Kepler, an orbiting observatory that’s looking for planets around other stars. It’s staring at about 100,000 stars, looking for dips in light from the stars that indicate orbiting planets that periodically block the stars’ light. The central star of Kn 61 – the blue dot in the middle of the cloud – is being examined to see if it’s a binary or not. Professional astronomers have partnered with amateurs to do this, and Matthias Kronberger is a Swiss amateur who discovered this beauty.
The image uses filters that select the light from ionized oxygen (emitted very strongly by such nebulae) and hydrogen. I love the barred spiral galaxy just adjacent to Kn 61; the planetary nebula is in our Milky Way galaxy, but that spiral is probably tens of thousands of times farther away.
The overall symmetry of the nebula is striking – in fact, it’s sphericity makes me inclined to think the star is not part of a binary; the centrifugal force of two stars revolving around each other tends to flatten such nebula and create bizarre shapes (see Related Posts below). The filaments creating the soccerball-like structure are probably due to the nebula expanding into surrounding gas, compressing it (or a faster wind from the stellar core that has caught up with and slammed into the slower-moving red giant wind). I’ve never seen any other planetary nebula that looks quite like this one though. It’s really fantastic, in the sense of the word “fantasy”: ethereal, strange, and beautiful.
Image credit: Gemini Observatory/AURA