Carl Knight. Mild mannered computer programmer by day. By night, an intrepid explorer of the night sky searching for unseen planets in other star systems.

I operate a small (9m^2) observatory in the rural Rangitikei district of New Zealand. My observing focus has shifted from highly evolved stars and star systems to Exoplanet transit timing.
I continue to get one to two high school students per year who do a variety of astronomy related projects with me as part of New Zealand education's CREST (CReativity in Engineering, Science and Technology) program.
I live with my wife and two of our recently returned adult children on 10 acres along with Rusty, Pepper, Domino and Carla (dogs), Poppy (house cow), a couple of goats, and too many geese, ducks and chickens.

Locating non-transiting exoplanets by transit timing variation

Most of the exoplanets we currently know of are a single transiting body from the perspective of Earth. That is, we can observe a cyclic dimming of the parent star by the transit of an exoplanet and no others. However, given theories of star system and planetary system formation, it seems unlikely that these stars play host to single bodies. Yet that is all we can observe. So we expect to find multiple bodies of all varieties of sizes in these star systems. How can we prove they exist? The answer is, we can detect their influence on the transiting bodies we can directly detect. This is where TTV (Transit Timing Variation) is used to hypothesise other likely non-transiting bodies in the same system as the transiting bodies. With modelling and constraints applied by other phenomena we can observe such as radial velocity, we can suggest additional bodies and orbital parameters capable of producing the observed transit time variations. These candidates can then be the target of observations by much more capable instruments.

Slides: Locating non-transiting exoplanets by transit timing variation