is science inherently sacred?

Nothing is inherently sacred to Stirner. That is one of the major points in Stirner's book, The Ego and Its Own. Egoism is a selfish refusal to honor the hallowed specters of ghost derived by modern philosophy and science. The central message of The Ego and Its Own is that it is up to the individual to discover and to fight for what and who they are. There are no moral absolutes or ideological reference points outside that reality and values chosen by the individual.

can science not be sacred?

The sacred is a social construct; it's a spook. The sacred is the "subordination of mind," "the criterion of alienation." While the contents of the sacred may differ by society and historical period, it always entails alien, fixed ideas and the renunciation of the ability of individuals to create mind, self, and society. Here, Stirner does not deny the existence of external causes. He denies their legitimacy. The purpose of external causes, such as god and mankind, is to eliminate the self as a competing cause or as an alternative source of allegiance. The practus of external causes is to extend their control by ensuring that individuals subordinate their values, meanings, and "concerns" to an allegiance to god, humanity, or some political ideology. Stirner's egoism, on the other hand, is an assertion that individuals are the source of creation, or the assignment of meaning and allegiance; and, thus, can legitimately base their thoughts and behavior on their own "concern." "Nothing is more me than myself" is the expression of Stirner's egoist rebellion against claims that external causes are the legitimate owners of the thought and behavior of the person. The basic question of the egoist challenge to the external cause is: Are social organizations the masters of individuals or the servants of persons?

Is he saying that instead of worshipping science, one should use it instead?

Not only to use it, but to make science one's own, to appropriate it, to consume it. Worship nothing.

In the process of socialization, individuals are expected and coerced to submit to the external, objective, sacred, and reified requirements for human thought. Likewise, people we lose the ability to create or to participate in the creation of knowledge. The person is relegated to the role of "learning," or fixated on an inert external object. The person is reduced to passively observing, knowing, or fathoming the object, instead of dissolving, using, or consuming the object as an active subject. What is" imparted" is objective, external, and alien, it is not "our own."

Ownness does not imply a lack of constraint. It is a type of action in which the person acquires and possesses ideas or objects as property. Most importantly they assert ownership over body, mind, and self. Ownness is an active seizure or appropriation of thoughts common values common and objects as the "property" of the individual. The individual must cultivate meaning for their own life. "Ownness" has no alien, external standard. It is only intended to be a description of the act of ownership by the person. The individual's task is not to realize the "essence" of man, humanity, a race, or a culture, but to live as a self-conscious self-determining person, to their life, mind, and self. The individual supersedes the species and, as such, is without norm, without law, and without model. All social, cultural, and political categories, including racial and cultural identities, are abstractions irreducible to the material reality of the real, living individual.

As long as individuals believe and act on the notion that fixed ideas and "essences" are superior, external, and unalterably constraining on them, or that their task in life is to fulfill an external idea, they are not egoists or owners. As individuals no longer serve any ideal, or any "higher essence" or" supreme being," they no longer serve any other person either, but become their own. Ownness refers to a commitment and effort on the part of the individual to behave on the basis of their choices. When individuals serve themselves they are owners or unique egoists.