A long time ago in a solar system far far away... Space exploration is a very interesting and wonderful science with so much interesting discoveries lately, especially for those playing around with sci-fi ideas, the greatest hit these days being the constant influx of exoplanet discoveries. The Kepler mission is one great source, and it also spotted something quite extraordinary.
The star identified as KIC 8462852 produces some very odd signal for which as of now we have no real rational explanation. Of course this isn't the first time something alike happens, the dicovery of pulsars also begun with something similar. Anyway, even if on the end it proves not to be some giant structure built by the Borg, the unraveling of the mystery will likely contribute greatly to our understanding of the universe, likely being something important.
But look at the distance data. Almost 1500 lightyears! For one, it is amazing how far we can see and collect sensible data from. The Kepler could spot an exoplanet even as much as nearly 9000 lightyears away! For another, it is scary to imagine that the data we see is already that old. Those rays of light by which we wonder about what happens around the KIC 8462852 emerged from the star around the time the Western Roman Empire fell!
The ways we discover exoplanets are no less scary. The Kepler uses the transit method, monitoring the stars whether there was a little dip in their luminosity suggesting a planet traversing in front of them. Of course it only works if the orbit aligns with the line of sight of the viewer (the only little deviance it permits is by the size of the occluded sun), and if you can wait for the occlusion to happen. Good chances to spot another Earth then from far-far away! Not to mention the myriad of factors, noise and stuff to rule out to make sure the dip was truly a planet. The Kepler, until it was capable to, kept gazing at a fixed spot, aiming to collect data to get an idea over the general probability and distribution of exoplanets.
There are many other methods, for example by astromety it is possible to discover exoplanets irrespective of the alignment of their orbit.
It is interesting to look up these, to have some rough idea on how the methods work, it's both scary and fascinating that we are capable to do these, to get some idea on worlds so far away. Wikipedia has very nice information on solar systems and exoplanets, but you should also look elsewhere. The exoplanets.org site can be quite useful trying to find observed planets.
If you wish to set a sci-fi in our galaxy using as much known, proven information as possible, these are definitely the way to go. It is even useful to craft fictional planets: you can find data on most nearby solar systems including what was attempted on them for searching exoplanets. There may be constraints already discovered, such as the lack of planets around or more than the mass of Jupiter in the habitable zone or nearer. So you shouldn't imagine an intelligent civilization on a moon of one in such a system. An other thing good to know is the characteristics of different stars, their ages: red dwarfs may be tempting as there are many and they are long lived, but they are also frequently (maybe always) flare stars, producing massive outbursts probably rendering the system incapable to support any form of life.
Anyway, this is a massive, interesting subject, new discoveries are always on the corner.