This image shows our Milky Way galaxy in visible light. The dark spots are dust clouds which block light.
Courtesy Astrophysics Science Division at the NASA Goddard Space Flight Center

This image shows the same view in X-ray light. X-rays pass right through the dust clouds. The puffy areas are gas clouds, hot enough to emit light. We see few stars, because most don’t emit a lot of X-rays.
Courtesy NASA/UMass/D.Wang et al.

In a darkened room, a computer screen glows. High above the atmosphere, NASA’s Chandra Observatory has detected X-ray light from a distant cluster of galaxies and beamed the information back to Earth.

X-rays generally come from very hot, high-energy sources: collapsed stars, such as neutron stars and black holes, or super-heated gas, the remnant of a violent explosion or other powerful event.

Astronomers like Megan study this information—where the X-rays come from, how intense they are. Computers compile the data to create images of this light we can’t see.

Studying these X-ray sources helps Megan see what’s going on in outer space. She’s particularly interested in the gas lying between galaxies, which is extremely hot but cools rapidly. Apparently, there is more matter in the gas than in the galaxies themselves! Strange things are happening in the gas clouds, and Megan hopes to sort it all out.

Chandra flies high to catch the waves

This artist’s rendering shows the Chandra observatory collecting X-ray images high above the Earth.
Courtesy NASA/CXC/SAO, Illustration by CXC/NGST

Stars, galaxies and clouds of gas all give off energy in the form of light. Some of this light we can see with our eyes, but much of it we can’t. X-rays are light waves with much higher frequencies than visible light.

The Earth’s atmosphere absorbs X-rays. In order to study them, NASA used the space shuttle to launch the Chandra Observatory in 1999. Designed to gather only X-ray light, it is the heaviest object ever launched by the shuttle.

Extremely sensitive, Chandra can record a single photon, or particle of light. It is so powerful it could read a stop sign from 12 miles away—if the sign were giving off X-ray light. This high resolution allows scientists to study galaxies in great detail, even though they lay millions of light-years away.

Use photos of celestial objects under different light to identify what they are.