1. A Galaxy Revealed in Multiple Wavelengths
Topic:
Multiwavelength observations
Concepts:
Infrared observations, X-ray observations, Optical observations, EM spectrum
Missions:
“Great Observatories”: Hubble, Chandra, Spitzer;
GALEX
Coordinated by
the NASA Astrophysics Forum
An Instructor’s Guide for using the slide sets is available at the ASP website

2. The Four Space Observatories Provide New Insights into M101
In 2012, GALEX ultraviolet observations added new insights into the structure of the Pinwheel Galaxy, M101.
Combined with previous Spitzer, Hubble, and Chandra observations, they produced a new multiwavelength view of the galaxy M101 combining infrared, visible, ultraviolet, and X-ray images, respectively, into a single picture.
M101 is often referred to as The Pinwheel Galaxy or NGC It is about 70% larger than our own Milky Way Galaxy, with a diameter of about 170,000 light years, and sits at a distance of 22 million light years from Earth.
Press release:
Press Release from 2009 IYA 3-component image:
3-component Image composed for International Year of Astronomy 2009 has associated resources and activities:
NASA’s Great Observatories are the Space Telescopes: Hubble (HST), Chandra (CXO), Spitzer (SST), and the Compton Gamma Ray Observatory (CGRO, decommissioned in 2000). The centers that operate these telescopes are Space Telescope Science Institute (STScI), Chandra X-ray Center (CXC), and Spitzer Science Center (SSC). ESA is the European Space Agency.
GALEX (Galaxy Evolution Explorer) detects ultraviolet (UV) wavelengths.
Messier 101 (M101) is a face-on spiral galaxy 22 million light years distant in the direction of the constellation Ursa Major and is 70% larger than our own Milky Way.
Credit: NASA/CXC/SAO, NASA/JPL-Caltech, NASA/STScI

3. How do Astronomers Learn More about M101?
Investigations across multiple wavelengths provides a more complete view of galaxies like M101:
Spitzer’s infrared view can show lanes of dust that congeal into stars—the brightest areas warmed by young, hot stars.
Hubble’s visible light view can reveal a galaxy’s stars and star clusters, and brownish dust lanes silhouetted against their glow.
GALEX’s ultraviolet view can locate hot, young stars that formed about 1 million years ago.
Chandra’s x-ray view can unveil the emission from supernova remnants, diffuse hot gas, and where gas spiraling into black holes is heated to extremes.
Press release captions:
Purple=Chandra: Sources of X-rays include million-degree gas, exploded stars, and material colliding around black holes.
Red=Spitzer: IR highlights the heat emitted by dust lanes in the galaxy where stars can form.
Yellow=Hubble: Most of this visible light comes from stars, and they trace the same spiral structure as the dust lanes.
Blue = The blue areas are ultraviolet light, given out by hot, young stars that formed about 1 million years ago.
EM spectrum figure:

4. The Big Picture
Spitzer Image:
Large Magellanic Cloud
Galaxies are made of various objects that emit in different wavelengths:
Types of stars: young and old, big and small
Diffuse gas
Interstellar dust
Exotic, high-energetic objects (e.g. black holes or neutron stars)
A complete understanding of how galaxies form and evolve with time, requires understanding all of these components
Some of them must be studied at different wavelengths.
Hubble Image: M51
Examples of galaxies studied across wavelengths are in the figure:
The Large Magellanic Cloud as imaged by the NASA Spitzer Space Telescope. The image is a composite of infrared light at wavelengths of 3.6 (blue), 8 (green) and 24 (red) µm. Credit: NASA Spitzer
M51 composite from HST. Credit: S. Beckwith (STScI) Hubble Heritage Team, (STScI/AURA), ESA, NASA
Multiwavelength composite Chandra image of the nearby galaxy Centaurus A provides one of the best views to date of the effects of an active supermassive black hole. Opposing jets of high-energy particles can be seen extending to the outer reaches of the galaxy, and numerous smaller black holes in binary star systems are also visible. Credit: NASA/CXC/CfA/R.Kraft et al.
These three galaxies have been studied extensively in various wavelengths to help astronomers better understand their evolutions.
Chandra Image: Centaurus A

5. How Does this Change our View?
Adding the GALEX UV view of M101reveals the true extent of the galaxy and shows us how many young, hot stars have recently formed in the outskirts of the galaxy’s disk!
Images taken in different wavelengths reveal different aspects and processes of galaxies like M101 and of the universe at large, allowing us to build a complete picture and understanding of the cosmos.
NASA’s science missions range across the electromagnetic spectrum to reveal this larger, deeper, and more fundamental view.
By “seeing” across the electromagnetic spectrum, our view of the universe is more complete, helping us to understand the true nature of the cosmos.
Composite
Ultraviolet
Infrared
Visible
X-ray
Animated slide: click through to compare the images.
Credit: NASA/CXC/SAO, NASA/JPL-Caltech, NASA/STScI

6. Resources Press release: Activities: Multimedia:
Activities:
Hubble’s Composite Images
Multimedia:
Video – combining the Hubble, Chandra, and Spitzer observations:
EM spectrum tour:
NASA’s IYA website:
Mission press releases:
Hubble
Chandra
Spitzer

7. A Galaxy Revealed in Multiple Wavelengths
BONUS CONTENT

8. NASA leverages the EM Spectrum
Credit: Goddard Space Flight Center
Observatories across the spectrum:
NASA has a fleet of telescopes that cover the electromagnetic (EM) spectrum, in order to observe the universe in different wavelengths.
Because Earth’s atmosphere blocks certain wavelengths of light, space-based (and stratospheric) observatories often complement the work of ground-based observatories.

9. What do the Colors Mean?
Spitzer
Hubble
GALEX
Chandra
Infrared
Visible
Ultraviolet
X-ray
Because human eyes cannot see in Infrared, Ultraviolet or X-ray, scientists assigned red, yellow, blue, and purple colors to Spitzer, Hubble, GALEX, and Chandra images, respectively.
Combining the four colors produces the final multiwavelength image that traces various astrophysical processes occurring in the M101 galaxy.
•Spitzer’s infrared view (red) shows lanes of dust that congeal into stars—the brightest areas warmed by young, hot stars.
•Hubble’s visible light view (yellow) shows the galaxy’s stars and star clusters, the brownish dust lanes silhouetted against their glow.
GALEX’s UV view (blue) show hot, young stars that formed about 1 million years ago.
Chandra’s x-ray view (purple) shows the location of supernova remnants, hot gas, and where gas spiraling into black holes is heated to extremes.