We've discussed circumstellar disks around young stars multiple times in this blog, but we haven't discussed how they are observed. Circumstellar disks are best visible at infrared and optical wavelengths. This is because the disks are made of dust and gas, which reflect optical starlight and emit thermal infrared light. Astronomers have used telescopes such as Hubble (optical) and Spitzer (infrared) to image many disks of young stars, but you don't necessarily need a space telescope to see these disks. An amateur astronomer named Ralf Olsen proved this by imaging the disk around the nearby young star Beta Pictoris! Armed with his backyard 10inch telescope, a PC webcam and no filters, Olsen was able to image the disk of Beta Pictoris by following a procedure outlined in a 1993 paper by Lecavelier Des Etangs and collaborators. Basically, Olsen imaged Beta Pictoris and a very similar star called Alpha Pictoris, then subtracted the Alpha image from the Beta. Since the stars have similar properties, subtracting the images effectively erased the light of Beta Pictoris, making its disk visible. The image below is the final result from Olsen.
The black circle is where Beta Pictoris was removed in the image, and its disk is the extended white region near the star that the dotted lines point to. It's really amazing what an amateur astronomer can do with a basic telescope! Olsen is living proof that you don't need to be a rocket scientist to understand, and even contribute research to the field of astronomy!
Image Credit: Rolf Olsen
