A Greenly Glowing Football in Space
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Friday, Aug. 16, 2013, at 8:00 AM
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.
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:
IC 1295, a weird, green, glowing fuzzball—or football—in space. Click to ennebulenate.
Photo by ESO
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.
IC 1295 is football shaped and seen at an angle, similar to this picture of an American football.
Photo by Shutterstock/David Lee
Photo by Shutterstock/David Lee
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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