There isn't a definitive "first lady astronomer" as the field has a long and diverse history, with many women making important contributions throughout time. However, some women are often cited as pioneers in the field:

Early Pioneers:

* Hypatia of Alexandria (c. 350-415 AD): While not exclusively an astronomer, she was a renowned philosopher, mathematician, and teacher who likely studied astronomy and contributed to its development.

* Caroline Herschel (1750-1848): She was a German-born astronomer who worked alongside her brother, William Herschel. She discovered several comets and nebulae, cataloged stars, and made significant contributions to astronomy.

Other Notable Women:

* Maria Mitchell (1818-1889): The first American woman to discover a comet, she was also a respected educator and advocate for women in science.

* Annie Jump Cannon (1863-1941): Known for her groundbreaking work on classifying stars, she developed the Harvard Classification System still used today.

* Henrietta Swan Leavitt (1868-1921): Her research on Cepheid variable stars led to a crucial understanding of the distance to other galaxies.

It's important to remember that many other women contributed to astronomy throughout history, and their achievements deserve recognition.

The field of astronomy has become increasingly inclusive, and women are now actively contributing at all levels of research and discovery.