Here is a worksheet on the Greek word roots astro and aster. They mean, as you have doubtlessly already inferred, star.
These are hard working roots in English, pushing into fruition words like asterisk, asteroid, astronaut, and astronomy.
If you find typos in this document, I would appreciate a notification. And, as always, if you find this material useful in your practice, I would be grateful to hear what you think of it. I seek your peer review.