Gale Encyclopedia of SciencePopular science magazines can be a good introduction to a topic, as they are easy to read but generally have information that is supported by peer-reviewed research. They may even be discussing a specific research article in popular language.
If your assignment is asking for peer reviewed journal articles, then you don't want to cite this type of source for your assignment. But it is useful for getting some ideas about your topic.
Here are some popular science magazines, try searching for your topic in each:
