It's not easy to take pictures of exoplanets for two reasons:
1) They are small and far away
2)They are very dim compared to the star they revolve around
Imagine you're standing in the end zone of a football field at night. Taking a picture of an exoplanet would be like trying to take a picture of a small moth fluttering in front of a stadium light at the other end of the field. The stadium lights are way too bright, and the moth is too small and far away to make out any details. The most common method used to "image" exoplanets is to look at light curves, which I will discuss on Thursday's post, but astronomers have actually discovered a way to take pictures of some exoplanet systems. To do this they use an instrument called a Vortex Coronagraph. This device was actually experimentally discovered by Grover Swartzlander, a physics/imaging science professor at the Rochester Institute of Technology! Simply put, the device "blocks" all the light from a star, allowing any planets around the star to appear very bright. It's a bit more complicated than it sounds, as the device doesn't really block the light, it uses mathematical tricks to polarize the light and cause the light waves to cancel each other out.
The picture above is of the exoplanet system around star HR8799 taken using a Vortex Coronagraph on the Hale 1.5m telescope. The star is where the green X is, and as you can see, it's light has been canceled out so that we can see three planets. Only a few exoplanets have been imaged this way, but as more discoveries are made and technology advances, we hope to directly image as many systems as possible.
