Question

달은 지구의 위성이에요 As a topicalizing particle, -은/는 cannot follow words bringing up a new topic. In first-person subject sentences, it is obvious that the speaker is talking about himself, so the subject is often marked with -은/는. Similarly, when talking about universally acknowledged facts, the subject is commonly followed by -은/는.

Accepted Answer

The Moon is a satellite of the Earth

Front	달은 지구의 위성이에요
Back	The Moon is a satellite of the Earth
Notes	As a topicalizing particle, -은/는 cannot follow words bringing up a new topic. In first-person subject sentences, it is obvious that the speaker is talking about himself, so the subject is often marked with -은/는. Similarly, when talking about universally acknowledged facts, the subject is commonly followed by -은/는.

Subject Talking 은/는 달은 지구의 위성이에요 Moon Satellite