A Greenly Glowing Dying Star, or a Gigantic Alien Protozoan?

Bad Astronomy
The entire universe in blog form
Aug. 16 2013 8:00 AM

A Greenly Glowing Football in Space

As long as I’ve been studying and reading about planetary nebulae—the expelled gassy shells from dying stars—it’s always a bit surprising that I can find one that a) I’ve never heard of, and 2) has a shape so odd it actually has me scratching my head.

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

IC 1295 is a green bauble floating in space about 3000 light years from Earth, and in this Very Large Telescope image you can see that it’s a bit weird:

ESO's VLT images the planetary nebula IC 1295
IC 1295, a weird, green, glowing fuzzball—or football—in space. Click to ennebulenate.

Photo by ESO

It looks more like something you’d see under a microscope than through a telescope! There are actually quite a few objects with a similar shape to this, but they’re usually more circular, not so oval. And it has a detached, thin shell, too, which is unusual as well—especially since it has the same elliptical shape as the material in side it.

football
IC 1295 is football shaped and seen at an angle, similar to this picture of an American football.

Photo by Shutterstock/David Lee

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It took me a second, but then I figured the physical shape of the gas must be a prolate ellipsoid—I love me some fancy words—which means a football shape (more like a rugby ball shape, really). A thin spherical shell of gas in space will look like a thin circle, a soap bubble, through a telescope, but the squashed nature of IC 1295 belies its true physical shape. If it’s elongated, and we see it at an angle, then it will look like a thin ellipse.

Nebulae like this form as a star dies, and starts to blow a wind into space. Over the years it sheds all of its outer layers, exposing the über-hot core, now called a white dwarf. You can see IC 1295’s central star, the sharp blue pinprick just to the left of the brighter, redder star (almost all the stars in this picture are in the foreground or background of the nebula itself).

When the star starts to blow that wind, it can compress the thin gas between stars. That’s what forms the thin shell that we see as a detached halo. Over time, the wind from the star speeds up, and slams into the gas expelled earlier. The inner fuzzy glow is from gas heated as that happened. All in all, the outer reaches of the nebula reach about two light years across, which is fairly typical.

I was surprised not to find much in the professional literature about this interesting and pretty object, though it was studied a few years back as part of a survey of similar nebulae. The press release for this image doesn’t link to any paper, either, but I hope such a detailed, deep, and frankly gorgeous image gets its due in the scientific process. After all, something like this will happen to the Sun in a few billion years, and learning about this process tells us more about our own eventual fate. Also—as is really true astronomically for every object we study—each planetary nebula we see is unique, and the more we know about them, the more interesting they become.

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