How did Andrea Ghez study stars near the Milky Way’s centre?

To study stars near the centre of the Milky Way Galaxy, Andrea Ghez utilized high-resolution imaging techniques to overcome the blurring effects caused by Earth’s atmosphere.1

Beginning in 1995 at the Keck Observatory in Hawaii, Ghez and her team employed two primary methods:

• Speckle imaging: This technique involves taking numerous images with very short exposure times and combining them to remove atmospheric distortion.1
• Adaptive optics: This advanced method physically adjusts the telescope mirror in real time to compensate for atmospheric turbulence.1

By achieving improved resolution through these techniques, Ghez was able to identify individual stars and track their orbits around the galactic centre. Her observations revealed that these stars were orbiting a massive, compact object coincident with the radio source Sagittarius A*, confirming it to be a supermassive black hole.1