Hot and Cold Andromeda Galaxy
The Andromeda galaxy is our Milky Way galaxy's nearest large neighbor. It is located about 2.5 million light-years away and holds up to an estimated trillion stars. Our Milky Way is thought to contain about 200 billion to 400 billion stars.
This image uses two different wavelengths to show the cooler clouds of star birth (orange) and hot, explosive, older stars (blue). The orange area is seen in infrared light and the blue in X-ray wavelengths. Astronomers use these wavelengths to see more than they can see with visible-light alone. They also assign colors to represent each wavelength, so stars would not appear in these colors if we could see them with our eyes.
The European Space Agency's Herschel Space Observatory and XMM-Newton telescope created this image. NASA plays a role in both of these missions.
Image credit: ESA/Herschel/PACS/SPIRE/J. Fritz, U. Gent; X-ray: ESA/XMM Newton/EPIC/W. Pietsch, MPE