What kind of stars make up the galactic nucleus?
We don't know
Right now the most accepted theory says that every galaxy has a supermassive black hole in its centre which is millions of times more massive than our sun
The galactic nucleus contains old stars and a supermassive black hole.
Recent observations of the nucleus of our galaxy and others have shown that most galaxies contain a supermassive black hole at their centres. These black holes are known to have a mass which is related to the mass of the galactic centre. The black holes are thought to control star creation.
It is also known that the stars in the galactic nucleus are very old. They are at least 10 billion years old.
The nucleus is also very densely populated with stars. They are typically red giant or post red giant stars.