How can you find out what scientists already know about a particular astronomy topic or object?
Searching the literature is an essential part of doing research. Reading the literature is different than reading a newspaper article.
Most coherent, developed, tested materials
Movie (21:54) on basics of astronomical literature searching (by Dr. Luisa Rebull, 2016)
Movie (15:57) on how to read scientific literature (by Dr. Luisa Rebull, 2016)
Movie (17:38) on a case study on how to read a scientific paper with a goal of getting data out. It was for one of my IC417 teams, so it uses a paper relevant to IC417. (by Dr. Luisa Rebull, 2016)
Important note about publications (by Dr. Luisa Rebull, 2020)
Literature: Observation and Inference by David Strasburger (NITARP alum)
Somewhat less coherent (or less standalone) materials
"How to read scientific posters" portion of this NITARP kick-off workshop talk (by Dr. Varoujan Gorjian; this version from the AAS workshop 2020)
Literature searching worksheet (by Dr. Luisa Rebull, circa 2009 but updated slightly)
Other sources of interest
Astrobites is an AAS-supported site that is run by grad students. Every day, they pick at least one article from arXiv and summarize what the article is discussing, including relevant background if relevant. This is a great way for anyone (you, your students) to keep current on astronomical literature. They tend to pick important articles, so even if you don't want to read their summaries of the journal articles, you can take their paper suggestions and read the papers completely on your own. There are also summaries of really important papers from the past, as well as guides for students on careers and graduate school, and basics about telescopes, etc. There are even materials on using Astrobites in classes; also see BiteScis. The same parent organization also has PERbites which summarizes physics education research articles.
AAS Nova is research highlights from the AAS journals. Some overlap with Astrobites above, but also some content unique to it.
Astronomy Paper Seminar Participation Guide & Reading Walkthrough, Cooke et al. (2020), written for an undergraduate and graduate student audience. (Incidentally, this is an example of an astronomy-relevant paper that only appears in arXiv, not in a journal.)