In a discussion about race and racism with a group of Black and Latinx students, the first part of the dialog centered around the things such as the difference between being African American and Black, or Hispanic versus Latinx. We meandered about for a while, and the conversation didn't gain focus until we talked about what it means to be white in America. Most observations about whiteness boiled down to having one's life valued more that those of people of color; the "value gap" as Prof. Eddie Glaude describes it. At that point it became clearer that our position in society defines our race. The processes that put us there is racism.
This brings up a subtle yet key point about race that is summarized nicely by Ta-Nehisi Coates: "race is the child of racism, not the father." Racism is a double standard that breaks along the line drawn by our society that places whiteness above, and non-whiteness below (I can never recommend Barbara Field's essay enough). Race is the set of narratives, customs and mental habits that justifies this stratification. Bringing the conversation back to the culture of astronomy, when we see white people overrepresented among the professoriate at the eye-popping rate of >90%, we need to be conscious of our narratives, customs and habits when we ask questions about this unnatural outcome. The tendency will be to ask, "Why aren't people of color advancing through our academic system?" or something similar. But we need to see our monochromatic demographics as what they factually are: we are seeing racism, not something that results from Blackness, Latinx-ness, or Muslim-ness, and our language needs to reflect this.
It's racism, not race. Race is extrinsically imposed, not intrinsically possessed. As such the answer cannot be diversity (or even racial justice*). It must be anti-racism, the process of learning about what features of our culture---yes, including the words and actions of the people in that culture---enact and maintain racism, and then learn how to subvert and counter those features until they are gone. A good place to start is by reading the book linked above (click on the image).
*I'll leave it as an exercise for the reader to prove that if race is a narrative used to justify an unjust society, that there can be no such thing, in a truly literal sense, as "racial justice."