A Planetary Nebula Pair

Spitzer_sig12-006_1024

spitzer_sig12-006 July 2nd, 2012

Credit: NASA/JPL-Caltech

How is it that two glowing globs of gas that look completely different can actually be basically the same thing? In the case of planetary nebulae like IC 4406 and NGC 2392, all it may take is a simple shift of perspective, provided here in infrared images taken by NASA's Spitzer Space Telescope.

When stars like our sun reach the end of their nuclear fuel burning lifetimes they make one final grab for glory. The outer layers of these stars, which have swollen to something approaching the size of Earth's orbit, get blown into space forming what has been dubbed a "planetary nebula." The expelled gas from the star glows brightly, illuminated by the ultraviolet light from the surviving stellar core, known as a "white dwarf."

The two planetary nebulae pictured here look oddly different from one another. IC 4404 takes on a very boxy, rectangular form while NGC 2392 looks more like concentric circles. If they are both the last gasps of dying stars, why would they appear so strikingly different?

It appears that stars commonly eject their material in winds that mostly blow out in opposite directions from their poles. This effectively carves out a cavity in the interstellar environment that is roughly cylindrical, or rod-shaped. If you look at this cylindrical cavity from the side, you would expect to see a boxy shape like IC 4406. On the other hand, looking into this cavity from the end, like looking straight into a pipe, you would expect to see something very circular, just like NGC 2392.

So even though these two planetary nebulae do not look similar at all, they may just be showing us what a dramatic difference a little change in perspective can bring.

The boxy IC 4406 is also known as the "Retina Nebula." It is found in the constellation Lupis. Estimates of its distance are somewhat uncertain, placing it anywhere from 2,000 to 5,000 light years away from us.

The rounder NGC 2392 is in the constellation Gemini and is around 3,000 light years away. The pioneering astronomer William Herschel first discovered it in 1787.

The somewhat misleading term "planetary nebula" actually comes from Herschel himself. After observing a number of round, fuzzy objects like NGC 2392, he thought their appearance was roughly similar to the newly-discovered planet Uranus. Because of that similarity, he applied the description of "planetary" to these nebulae.

The term has stuck, even though we now know these stellar remnants have little to do with planets. The only connection is that some of the elements recirculated back into interstellar space may one day end up forming new stars and planetary systems.

Provider: Spitzer Space Telescope

Image Source: http://www.spitzer.caltech.edu/images/5186-sig12-006-A-Planetary-Nebula-Pair

Curator: Spitzer Space Telescope, Pasadena, CA, USA

Image Use Policy: http://www.spitzer.caltech.edu/info/18-Image-Use-Policy

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Image Details

Image Type
Observation
Object Name
Retina Nebula IC 4406 NGC 2392
Subject - Milky Way
Nebula > Type > Planetary

Color Mapping

  Telescope Spectral Band Wavelength
Blue Spitzer (IRAC) Infrared (Near-IR) 3.6 µm
Green Spitzer (IRAC) Infrared (Near-IR) 4.5 µm
Red Spitzer (IRAC) Infrared (Mid-IR) 8.0 µm
Spectrum_base
Blue
Green
Red
Spitzer_sig12-006_1280
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ID
sig12-006
Subject Category
B.4.1.3.  
Subject Name
Retina Nebula, IC 4406, NGC 2392
Credits
NASA/JPL-Caltech
Release Date
2012-07-02
Lightyears
Redshift
Reference Url
http://www.spitzer.caltech.edu/images/5186-sig12-006-A-Planetary-Nebula-Pair
Type
Observation
Image Quality
Good
Distance Notes
Facility
Spitzer, Spitzer, Spitzer
Instrument
IRAC, IRAC, IRAC
Color Assignment
Blue, Green, Red
Band
Infrared, Infrared, Infrared
Bandpass
Near-IR, Near-IR, Mid-IR
Central Wavelength
3600, 4500, 8000
Start Time
Integration Time
Dataset ID
Notes
Coordinate Frame
Equinox
Reference Value
Reference Dimension
Reference Pixel
Scale
Rotation
Coordinate System Projection:
Quality
FITS Header
Notes
Creator (Curator)
Spitzer Space Telescope
URL
http://www.spitzer.caltech.edu
Name
Email
Telephone
Address
1200 E. California Blvd.
City
Pasadena
State/Province
CA
Postal Code
91125
Country
USA
Rights
http://www.spitzer.caltech.edu/info/18-Image-Use-Policy
Publisher
Spitzer Science Center
Publisher ID
spitzer
Resource ID
sig12-006.tif
Metadata Date
2020-07-23
Metadata Version
1.2
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Detailed color mapping information coming soon...

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There is no distance meta data in this image.