By Stacy Palen

The Milky Way is tearing apart the Sagittarius dwarf galaxy. Gaia observations of the resulting tidal streams permit sufficient accuracy to detect the influence of the Large Magellanic Cloud on the interaction. Simulations show that the Milky Way’s dark matter halo is complex.

Below are some questions to ask your students based on this article.

1). Prior to this study, what was known about the shape of the dark matter halo?

Answer: Not much. Different simulations found various shapes, some more symmetric than others.

2). In this study, what is new that allows astronomers to build a more detailed picture?

Answer: The Gaia satellite pinpoints the location of stars with truly unprecedented accuracy.

3). The following questions cannot be answered directly from the article but can be answered with a Google search. The paper discussed in this article was posted to the preprint server arXiv. What is a preprint?

Answer: It is a full draft that has not been peer reviewed.

4). In the process of scientific publication, what comes after the preprint stage?

Answer: The article undergoes formal peer review, and then it might be published.

5). What is the advantage of preprints?

Answer: They give access to the most up-to-date research.

6). Should you treat the results discussed here with more or less skepticism than the results published in a peer-reviewed journal?

Answer: You should treat them with more skepticism.

7). How could you know if the results held up to peer review?

Answer: You could search for the authors’ names or the topic in a database of journal articles.