Celestial Bodies Database

Why do I get the message: each star should have a foreign key that references one of the rows in galaxy. ?
I thought that the following code met the requirement:

                                          Table "public.galaxy"
+-----------------+-----------------------+-----------+----------+-------------------------------------------+
|     Column      |         Type          | Collation | Nullable |                  Default                  |
+-----------------+-----------------------+-----------+----------+-------------------------------------------+
| galaxy_id       | integer               |           | not null | nextval('galaxy_galaxy_id_seq'::regclass) |
| name            | character varying(80) |           | not null |                                           |
| number_of_stars | integer               |           |          |                                           |
| stellar_mass    | numeric               |           |          |                                           |
| spiral_galaxy   | boolean               |           |          | false                                     |
| active_galaxy   | boolean               |           |          | false                                     |
| notes           | text                  |           |          |                                           |
+-----------------+-----------------------+-----------+----------+-------------------------------------------+
Indexes:
    "galaxy_pkey" PRIMARY KEY, btree (galaxy_id)
    "galaxy_id" UNIQUE CONSTRAINT, btree (galaxy_id)
Referenced by:
    TABLE "star" CONSTRAINT "star_galaxy_id_fkey" FOREIGN KEY (galaxy_id) REFERENCES galaxy(galaxy_id)


                                             Table "public.star"
+---------------------+-----------------------+-----------+----------+---------------------------------------+
|       Column        |         Type          | Collation | Nullable |                Default                |
+---------------------+-----------------------+-----------+----------+---------------------------------------+
| star_id             | integer               |           | not null | nextval('star_star_id_seq'::regclass) |
| name                | character varying(80) |           | not null |                                       |
| star_mass           | numeric               |           |          |                                       |
| star_age            | integer               |           |          |                                       |
| variable_brightness | boolean               |           |          | false                                 |
| pulsar              | boolean               |           |          | false                                 |
| galaxy_id           | integer               |           |          |                                       |
| notes               | text                  |           |          |                                       |
+---------------------+-----------------------+-----------+----------+---------------------------------------+
Indexes:
    "star_pkey" PRIMARY KEY, btree (star_id)
    "star_id" UNIQUE CONSTRAINT, btree (star_id)
    "star_name_key" UNIQUE CONSTRAINT, btree (name)
Foreign-key constraints:
    "star_galaxy_id_fkey" FOREIGN KEY (galaxy_id) REFERENCES galaxy(galaxy_id)
Referenced by:
    TABLE "asteroid" CONSTRAINT "asteroid_star_id_fkey" FOREIGN KEY (star_id) REFERENCES star(star_id)
    TABLE "planet" CONSTRAINT "planet_star_id_fkey" FOREIGN KEY (star_id) REFERENCES star(star_id)