The center of our Milky Way galaxy cannot be seen with the eye alone. That’s because our galaxy is a dusty place. Until now, that dust has clouded our view in optical light.
The image at the top of this post is a view of the center of the Milky Way at infrared wavelengths. It was made by NASA’s Spitzer Space Telescope. We humans can’t see at infrared wavelengths, but this telescope can. Plus infrared imaging is now used extensively for military and civilian purposes. For example, in those cool night vision glasses you sometimes see in movies essentially give people infrared vision. The image at right shows what people would see if they could view a person at infrared wavelengths. Astronomers now routinely view the universe in the infrared as well, and at these wavelengths the Milky Way’s dust is not a problem. We can see all the way to our galaxy’s core.
In 2008, the Spitzer Space Telescope was used to create a mosaic image of the center of our Milky Way galaxy. Some still call it the most detailed image of our galaxy’s center made to date. This image was made by piecing together over 800,000 separate images. At these wavelengths – in this image – astronomers were able to see all the way through the galaxy for the first time. The same Spitzer data used to obtain this image, by the way, has also been used to catalog over 100 million stars at infrared wavelengths. Highlights of the data include new glimpses of stars forming that are over a hundred times as massive as our sun. As Barbara Whitney of the Space Science Institute in Boulder, Colorado told us about this research, “You know, astronomy is not just numbers, and facts and figures. It’s beautiful.”
Here’s another amazing image of the center of our Milky Way galaxy. This one is made at radio wavelengths with the the Very Long Baseline Array – or VLBA – which is a system of ten radio telescopes scattered across Earth’s globe and controlled remotely from Socorro, New Mexico by the National Radio Astronomy Observatory. (Image credit: NRAO/AUI/NSF, Jun-Hui Zhao, W.M. Goss.)
This image shows what may be the most tantalizing object in our entire galaxy. It’s called Sagittarius A* (pronounced A-star), and it’s located in the exact center of the Milky Way. This image shows Sagittarius A* as a bright white dot at center. Why a dot? The object this dot represents is invisible to the eye. It’s thought to be a supermassive black hole located at our galaxy’s core. Using the VLBA, astronomers found that a radio-wave-emitting object at the galaxy’s center would nearly fit between our Earth and sun. This is half the size measured in any previous observation.
Want to know more about this? Here’s a 90-second – or 8-minute – interview with Andrea Ghez about the black hole at the center of our galaxy.
So the center of our Milky Way galaxy is now better known than it was just a few decades ago. Still, can any of these images replace the view of the Milky Way with the eye alone on a clear dark summer night? You might not be able to see the center of the galaxy itself, but you can see a hazy disk that swells with stars in the direction to the galaxy’s center. It’s awesome! Try going to a dark location on a summer evening soon to peer in the direction of the center of the Milky Way with your own eyes.