Scientists search for planets around distant stars by detecting a slight wobble in the star's motion: the planet tugs on the star, making its light shift slightly toward the blue and then toward the red. But stars have their own ripples — dark spots and bright faculae on their surfaces. These also shift the light, making it hard to tell them apart from a planet.
The Sun is the only star where we can see these spots in detail. The researchers took images of the solar surface and identified active regions using a new method, like sifting the image through a fine sieve, keeping only sharp contours. Then they calculated on a computer how these regions should affect the Sun's light and wobble.
The same trick can be applied to other stars. If the model reproduces solar disturbances well, it can be trusted where spots are not visible. This way, astronomers can rule out false signals and more reliably find planets the size of our own.
Sunspots are about 1500 degrees cooler than the surrounding surface, which is why they look dark, even though they are still scorching at 3500 degrees.
In Arthur C. Clarke's novel "Rendezvous with Rama," astronomers accidentally notice a strange object because it does not look like the usual noise from stellar activity.