Read the following text and answer the question.

A galaxy is a collection of stars and other astronomical bodies, including planets, comets, and asteroids, held together by gravity.

Galaxies comes in different shapes and sizes. These include the spiral, barrel-spiral, and elliptical. Our galaxy called the Milky Way is approximately 100.000 light-years in the width and contains over 100 billion stars.

The center of galaxies can contain many young, very hot stars as well as older stars. Swirling clouds that have been energized by magnetic forces also exist in the center.

At this point in time, no one know the exact number of galaxies in the universe. Astronomers are, however, learning more and more about them every day.

Source: sites.google.com

Which verbs are not correct based on the paragraph above?