La kometo moviĝas tra la universo.

La is the Esperanto definite article, meaning the.

A few useful points:

• It never changes form.
• It does not agree with number or gender.
• Esperanto has no indefinite article like a/an.

So:

• la kometo = the comet
• la universo = the universe

If you said just kometo, that could mean a comet or simply comet depending on context.

In Esperanto, all singular nouns end in -o.

So:

• komet-o = comet
• univers-o = universe

This is one of the most regular parts of Esperanto grammar. Related forms are:

• -oj for plural: kometoj = comets
• -on for singular accusative: kometon
• -ojn for plural accusative: kometojn

So the -o tells you right away that these words are nouns.

This is a very common question.

• movi = to move something
• moviĝi = to move, to move oneself, to be in motion

So:

• La kometo movas... would suggest the comet is moving something else
• La kometo moviĝas... means the comet itself is moving

The key part is -iĝ-, which often makes a verb intransitive or gives the idea of becoming or undergoing a change.

Here the structure is:

• mov- = move
• -iĝ- = become / get into a state / move oneself
• -as = present tense

So moviĝas is the natural form for is moving / moves.

-as is the Esperanto present-tense ending.

So moviĝas means moves or is moving, depending on context.

A helpful rule:

• -as = present
• -is = past
• -os = future

And verbs do not change for person or number. For example:

• mi moviĝas = I move / am moving
• vi moviĝas = you move / are moving
• la kometo moviĝas = the comet moves / is moving
• ili moviĝas = they move / are moving

The verb ending stays the same.

It can mean either one.

Esperanto -as often covers both the English simple present and present progressive, depending on context.

So La kometo moviĝas tra la universo can be understood as:

• The comet moves through the universe
• The comet is moving through the universe

Usually context tells you which English translation sounds best.

If someone really wanted to emphasize an ongoing action, Esperanto has other ways to do that, but in normal usage moviĝas is enough.

Tra means through.

It is used when something passes from one side of a space, area, or medium to another, or moves within and across it.

Examples:

• tra la arbaro = through the forest
• tra la fenestro = through the window
• tra la universo = through the universe

So in this sentence, tra shows the path of movement.

Because tra is a preposition, and the noun after a preposition normally does not take the accusative -n.

So:

• tra la universo = through the universe

The -n ending is usually used for a direct object or for certain directional uses, but here the preposition tra already shows the relationship clearly.

So the normal form is:

• La kometo moviĝas tra la universo.

not

• La kometo moviĝas tra la universon.

A simple English-friendly guide is:

moh-VEE-jahs

More exactly:

• mo as in more without the r
• vi = vee
• ĝ sounds like the j in judge
• as = ahs

Also, Esperanto stress is almost always on the second-to-last syllable, so the stress is on vi:

mo-VI-ĝas

One more detail: ĝ is a separate letter in Esperanto, and it always has that j sound as in judge.

Not completely.

The sentence uses the most neutral, common order:

• La kometo = subject
• moviĝas = verb
• tra la universo = prepositional phrase

So this is standard subject–verb–rest order.

Because Esperanto uses endings to show grammar, word order is more flexible than in English. You could rearrange it for style or emphasis, for example:

• Tra la universo moviĝas la kometo.

That is still understandable, but the original sentence sounds more neutral and straightforward.

Yes. Kometo is essentially the Esperanto form of comet.

Many Esperanto words are internationally recognizable, but they are adapted to Esperanto spelling and endings:

• English comet
• Esperanto kometo

The changes are typical:

• c often becomes k
• nouns get the ending -o

So an English speaker can often recognize words like this, even though they follow Esperanto spelling rules.