Iam horizontem contemplabamur, cum cometes subito apparuit.

Contemplabamur is imperfect indicative, first person plural.

The imperfect is used for an action that was ongoing in the past, rather than a single completed event. So here it gives the background scene: we were watching / gazing at / observing the horizon.

That fits very naturally with what comes next: while that ongoing action was in progress, something else happened.

Because contemplor, contemplari is a deponent verb.

A deponent verb:

• has passive forms
• but an active meaning

So contemplabamur literally looks like a passive form, but it means we were contemplating / watching, not we were being contemplated.

This is a very common source of confusion for English speakers.

Because contemplor takes a direct object in the accusative.

So Latin says, in effect:

• the horizon we were watching

where English prefers:

• we were looking at the horizon

In other words, English needs at, but Latin does not here.
So horizontem is accusative singular, the direct object of contemplabamur.

Iam usually means already, by now, or sometimes now depending on context.

In this sentence, already is the most natural sense. It suggests that the action of watching the horizon was already underway before the comet appeared.

So it helps set the scene:

• we were already watching the horizon...

Apparuit is perfect indicative, third person singular, from appareo.

The perfect here presents the comet’s appearance as a single completed event:

• it appeared

This contrasts nicely with the imperfect contemplabamur:

• contemplabamur = ongoing background action
• apparuit = sudden foreground event

That is a very common storytelling pattern in Latin.

They create a classic background + interruption pattern:

• contemplabamur = what was going on
• apparuit = what happened during that ongoing action

So the sense is:

• We were watching the horizon, when suddenly a comet appeared.

English often uses was/were ... -ing for the background and a simple past verb for the interrupting event. Latin often uses imperfect + perfect for the same effect.

Because cum here is simply temporal: when.

When cum just means when and introduces a straightforward event in time, Latin can use the indicative. That is what we have here with apparuit.

A cum with the subjunctive often has a more literary or interpretive feel, such as:

• when
• since
• although with background or circumstantial nuance.

But here the sentence is straightforward:

• when the comet appeared

So the indicative makes good sense.

Cometes is the nominative singular form, so it is the subject of apparuit.

It looks unusual because it is a Greek-derived noun. Its nominative singular ends in -es, even though it is singular.

So:

• cometes = a comet as subject
• apparuit = appeared

Together:

• the comet appeared

This is one of those places where Latin noun endings do not always match the most familiar beginner patterns.

Yes, but in a very normal Latin way.

Latin word order is much more flexible than English word order because the endings show the grammatical relationships. Here the arrangement does a few useful things:

• Iam comes first and sets the scene immediately.
• horizontem contemplabamur keeps the object close to the verb.
• cum cometes subito apparuit places subito right before apparuit, which helps emphasize the suddenness.

English relies much more on fixed order; Latin can use order more for focus, rhythm, and emphasis.

Grammatically, contemplabamur does come from the verb that gives English contemplate, but in this sentence we contemplated is probably not the best translation.

Why not?

• English contemplated often sounds like a completed mental act.
• The Latin imperfect here suggests an ongoing visual action.

So depending on context, better English choices would be:

• we were watching
• we were gazing at
• we were observing
• we were looking at

The exact choice depends on the tone of the passage.

It is a real Latin word, but it is also a borrowing from Greek.

That is why it may not look like the most familiar Latin vocabulary. In this sentence it is the accusative singular form.

So even if the word itself feels a bit unfamiliar, its grammar is straightforward here:

• horizontem = direct object of contemplabamur