In a galaxy a long time ago and not so far away, there was a gigantic explosion.
The explosion occurred over two million years ago here in our own galaxy, the Milky Way.
Using the Hubble Space Telescope, astronomers studied the remnants of this eruption. It produced billowing gas clouds that tower 30,000 light‑years above and below the plane of our galaxy. For a distance comparison, it's only about two light‑years from our sun to the edge of our solar system.
The enormous structure was discovered as a gamma‑ray glow, invisible to the human eye, but detected by the space telescope. The explosion was located in the direction of the galactic center. Its balloon‑like features were confirmed by the X‑rays and radio waves that they were emitting.
To find out more about the gigantic bubbles, scientists used Hubble's Cosmic Origins Spectrograph to study ultraviolet light from quasars located behind the bubbles. As a quasar's light travels through the bubble, scientists use it to measure the velocity, composition, and temperature of the expanding gas inside.
The information gathered from one quasar's light has determined that the gas is about 17,000 degrees Fahrenheit, and is rushing from the galactic center at roughly two million miles an hour. It contains silicon, carbon, and aluminum, indicating that the gas was produced inside exploding stars.
Scientists are working to pinpoint the cause of the explosion. It may have been produced by a star‑making frenzy near the galactic center that formed many supernovas, or by a group of stars falling into the Milky Way's super‑massive black hole.
"Hubble Discovers that Milky Way Core Drives Wind at 2 Million Miles Per Hour" (HubbleSite)