Although on average we have been doubling our capability every ten months, it’s not like new discoveries are a regular progression. You go along and then suddenly there’s a big leap in what you can do, such as a new telescope in space. When you make that big leap, you’re going to blunder onto things that are big surprises. It’s not like you’re just hunting around for new surprises; you can’t avoid them.
As an illustration IRAS discovered planetary systems around other stars in the form of what are called planetary debris discs, systems of dust created when small bodies like asteroids collide with each other while in orbit around other stars. The first example was around the bright star Vega. IRAS looked at Vega in infrared light to calibrate the instrument, because we thought we knew how bright Vega was, but we found that Vega was ten times brighter than we expected it to be at long infrared wavelengths. It really makes the point that it wasn’t that somebody sat down and said, well maybe stars have these debris discs around them, I’m going to go search for them. It was a calibration source that didn’t work as a calibration source.
One way of putting it is to say that what was found around Vega is basically the analogous to the Kuiper belt in the solar system. The Kuiper belt is a large ring of icy debris around our Sun, in the outer solar system. The ring of debris around Vega was discovered a decade before our own Kuiper belt was discovered. We found an analog of a component of our own planetary system around other stars before we knew that we had this component. So that’s one big surprise.
Vega Debris Disk: Vega is the second brightest star in the northern night sky. The Spitzer Space Telescope and the Herschel Space Observatory contributed to the discovery of an asteroid-like belt of debis around the star, similar to the Kuiper Belt in our own system. Scientists theorize that the gravity of multiple planets orbiting the star may be sculpting the debris into its orbit.