For this class you'll be using the citation style used by Monthly Notices of the Royal Astronomical Society (MNRAS). This journal and others in astronomy use the Harvard - author (year) style. The following guide from MNRAS explains how to format your citations.
The Instructions to Authors from MNRAS gives more information on formatting figures and tables, references and more.
Keep in mind that the bibliography should be in alphabetical order (not in order of citation).
Citations in the text should be listed by name using the Harvard author (year) style. e.g. Smith & Jones (1991).
Citation Builders
You can use a citation builder such as Citation Machine or BibMe to help format your references.
To find the correct style, select the "More" tab and search for this style:
Citation Managers can help you to format your bibliography, keep your citations organized and store articles by whatever subject headings you choose. Endnote works easily with Web of Science. Be sure to create an account and install the plug-ins before you begin. Instructions can be found in the How-To Guide.
The TriCo Citation Guide gives more information on citation managers and builders.