Planeta jest daleko.

Because daleko is an adverb, and in Polish you normally use it to say that something is far away:

• Planeta jest daleko. = The planet is far away.
• Dom jest daleko. = The house is far away.

Daleka is an adjective. It would describe a noun, for example:

• daleka planeta = a distant planet

So in this sentence, Polish uses the adverb daleko, not an adjective agreeing with planeta.

Yes, in normal standard Polish, jest is needed.

Polish usually does not omit the present-tense form of to be in ordinary sentences like this. So:

• Planeta jest daleko. = correct
• Planeta daleko. = not the normal full sentence; it may sound incomplete, very colloquial, or stylistically reduced

So if you are learning standard Polish, use jest.

It is nominative singular.

That is because planeta is the subject of the sentence, and subjects are normally in the nominative case in Polish.

Also, planeta is a feminine noun.

So here:

• planeta = nominative singular feminine

Because Polish has no articles.

So planeta can mean:

• a planet
• the planet

The exact meaning depends on context. English forces you to choose a or the, but Polish usually does not.

A simple English approximation is:

plah-NEH-tah yest dah-LEH-koh

A few helpful points:

• Planeta has stress on ne: pla-NE-ta
• jest sounds roughly like yest
• daleko has stress on le: da-LE-ko

Polish stress is usually on the second-to-last syllable, and that pattern appears in planeta and daleko.

Yes, Polish word order is more flexible than English, but the neutral order here is:

• Planeta jest daleko.

Other orders are possible, but they change the emphasis or sound more marked:

• Daleko jest planeta. = possible, but more emphatic or literary
• Jest daleko planeta. = unusual in ordinary speech

So as a learner, the safest and most natural version is Planeta jest daleko.

Daleko means far or far away.

It is the opposite of blisko (near).

Examples:

• Planeta jest daleko. = The planet is far away.
• Szkoła jest blisko. = The school is near.

You can also modify it:

• bardzo daleko = very far
• dość daleko = quite far

Yes, absolutely.

That means The planet is very far away.

You can place adverbs like bardzo before daleko:

• Planeta jest bardzo daleko.
• To jest dość daleko.

So daleko works very naturally with words like bardzo, trochę, or dość.

You would say:

• Planeta jest daleko od Ziemi.

Here, od means from, and after od, Polish uses the genitive case.

So:

• Ziemia → Ziemi

This is a very common pattern:

• daleko od domu = far from home
• daleko od miasta = far from the city

Yes, but it means something slightly different in structure.

• daleka planeta = a distant planet
• Planeta jest daleko. = The planet is far away

So:

• daleka is an adjective directly describing the noun
• daleko is an adverb used in the sentence predicate

Both are correct, but they are not interchangeable in the same grammar pattern.