The Secret in the Stars (Nancy Drew, Book 156) by Carolyn Keene

But when Nancy finds Steller's van deserted and runs into a hostile rival of the astronomer, she senses a dangerous black hole in the event. Then Dr. Steller finally appears -- or is he an optical illusion? As Nancy uncovers more evidence, her suspicions lead her into a sinister scheme moving faster than the speed of light!

Reader Reviews
So suspenseful!!!!!, December 23, 2002 Reviewer: An Amazon.com Customer I loved this book. I had to rate this 5 stars. In this book Nancy and her friends are excited when Bob Steller an astronomer comes to do stargazing shows. But when he doesn't know information about astonomy it leads Nancy and her friends in a world of mix-up they never would've suspected.