Learn Hardcore Finnish: Opin uuden tähdistön nimen katsomalla karttaa, jossa kaikki tähdet oli piirretty tarkasti. - I learned the name of a new constellation by looking at a map where all the stars had been drawn carefully.

In Finnish, when you have a chain like “the name of a new constellation”, every noun and the adjective in front of the head noun go into the genitive:

uuden = of a new (genitive of uusi)
tähdistön = of a constellation (genitive of tähdistö)
nimen = name (genitive of nimi)

So:

uuden tähdistön nimen = the name of a new constellation

This is normal for possessive / “of X” structures:

ystäväni auton avain → ystäväni auton avain = the key of my friend’s car
(all the “owners” before the last noun are in genitive)

Here, nimi is the “main” noun (what did you learn? a name), and uusi tähdistö is just specifying which name, so they all come out as a genitive chain.

Why is it opin and not something like opiskelin?

Finnish has two common verbs here:

oppia = to learn (to acquire knowledge/skill)
opiskella = to study (to engage in study as an activity)

In this sentence:

Opin uuden tähdistön nimen…
→ I learned the name of a new constellation…

You oppia a concrete thing/skill:

Opin nimen. = I learned the name.
Opin suomea. = I learned (some) Finnish.

You opiskella a subject (more about the ongoing activity of studying):

Opiskelin tähtitiedettä. = I studied astronomy.

Here you’re talking about the result (you ended up knowing the name), so oppia is the natural choice.

Is opin present tense or past tense here?

Opin can be either present or past for this verb; Finnish uses the same form in 1st person singular:

Minä opin nopeasti.
→ I learn quickly or I learned quickly (context decides)

In your sentence:

Opin uuden tähdistön nimen katsomalla karttaa, jossa kaikki tähdet oli piirretty tarkasti.

The subordinate clause has oli piirretty (had been drawn), which is clearly past, so the natural reading is:

I learned the name of a new constellation…

So grammatically it can be both, but here the context strongly suggests past.

Why is it nimen (genitive) and not nimeä (partitive) after opin?

With oppia, the object case reflects whether the learning is seen as complete or ongoing / partial:

Opin uuden tähdistön nimen.
→ I learned the name of a new constellation. (you reached the end point; now you know it)
Opin uuden tähdistön nimeä.
→ would suggest you were in the process of learning the name (not complete), or learning it a bit / in some respects — it’s unusual here and would need very specific context.

Because the sentence clearly expresses a completed result, the total object (genitive nimen) is used.

What exactly is katsomalla, and how is it formed?

Katsomalla is a non-finite verb form (an infinitive form):

Base verb: katsoa = to look (at), to watch
3rd infinitive stem: katsoma-
Adessive ending: -lla

→ katsomalla = by looking, by means of looking

Function:

It expresses means or manner: how something is done.
It’s like English “by doing X”:
- Opin tämän lukemalla. = I learned this by reading.
- Opin nimen katsomalla karttaa. = I learned the name by looking at the map.

The subject of katsomalla is the same as the main clause subject (minä, implied in opin).

Why is karttaa in the partitive (not kartta or kartan) after katsomalla?

The object of katsoa is very often in the partitive, especially when you are just “looking at” something as an ongoing activity:

Katson karttaa. = I’m looking at the map.
Katsoin elokuvaa. = I was watching a movie.

Partitive here signals:

an ongoing / unbounded activity (you’re just looking, not “completing” the map),
and with perception verbs like katsoa, the partitive object is simply the normal idiomatic choice.

Kartan (genitive/accusative) would suggest a more “complete” action on the whole map and is not natural here. So katsomalla karttaa is the standard way to say “by looking at the map.”

Why does the relative pronoun appear as jossa and not jolla or missä?

Jossa is the inessive form (in which) of the relative pronoun joka:

joka = which / that / who
jossa = in which (inessive: -ssa/-ssä)
jolla = on which / with which (adessive: -lla/-llä)

In the sentence:

karttaa, jossa kaikki tähdet oli piirretty tarkasti
Literally: a map, in which all the stars had been drawn carefully

The idea is that the stars are drawn in the map, inside its image/space.

You could also talk about things “on the map” with kartalla / jolla, but jossa focuses on the map as a sort of contained image, a space in which the stars are placed. It’s a very natural choice here.

Why is the head noun karttaa in the partitive, but the relative pronoun is jossa (inessive), not some kind of partitive form?

The case of the head noun and the case of joka are decided independently:

karttaa is in partitive because it is the object of katsomalla:
- katsomalla karttaa = by looking at the map (object of katsoa → partitive)
jossa is in inessive because inside the relative clause it plays the role of a location (in which):
- jossa kaikki tähdet oli piirretty
  → in which all the stars had been drawn

So:

The main clause chooses karttaa (partitive object).
The relative clause chooses jossa (inessive location). They don’t have to, and usually don’t, share the same case.

Why is it tähdistön and not just tähden or tähdet?

Different words:

tähti = star
- tähden (gen.) = of a star
- tähdet (pl.) = stars
tähdistö = constellation (a collection/group of stars)
- tähdistön (gen.) = of a constellation

The phrase uuden tähdistön nimen means:

the name of a new constellation, not the name of a new star.

If you said:

uuden tähden nimi = the name of a new star (one star)
uuden tähdistön nimi = the name of a new constellation (pattern/group of stars)

In jossa kaikki tähdet oli piirretty tarkasti, why oli piirretty and not just piirrettiin?

Two different tenses/structures:

piirrettiin = past passive (simple past)
- kaikki tähdet piirrettiin = all the stars were drawn
oli piirretty = past perfect passive
- literally: had been drawn

In jossa kaikki tähdet oli piirretty tarkasti, the past perfect passive:

emphasizes the resulting state: at the time when you looked at the map, the stars were already in the state of having been drawn.
links nicely with opin as a later event:
- the drawing had happened before you learned the name.

So it’s like:
“…a map in which all the stars had been drawn carefully.”

Why is it oli piirretty (singular) even though kaikki tähdet is plural? Shouldn’t it be olivat piirretty?

Oli piirretty is a passive form, and in Finnish passive:

The verb does not agree in number with any noun.
There is no expressed subject like “they” or “people”; it’s more like “it had been drawn” / “was drawn” in English.

Compare:

Tähdet oli piirretty tarkasti.
→ The stars had been drawn carefully. (passive, no subject)
Tähdet olivat piirtäneet kuvan.
→ The stars had drawn the picture. (active; here the stars themselves are the plural subject)

So oli piirretty is a fixed passive construction, and it stays singular regardless of kaikki tähdet.

Why are tähdet in the nominative, not in some object case, if they are what was drawn?

In the perfect / pluperfect passive (forms like on piirretty, oli piirretty), the “logical object” often appears in the nominative, not in the usual object case:

Kaikki tähdet oli piirretty tarkasti.
→ literally: All the stars had been drawn carefully.
Kuva on otettu.
→ The picture has been taken.

This is because the structure focuses on the resulting state: the stars are in the state of having been drawn. Grammatically, tähdet behaves more like a subject complement of this passive-result construction, so it shows up in nominative plural.

How does tarkasti relate to tarkka? Why the ending -sti?

Tarkka is an adjective: exact, accurate.

To turn many adjectives into adverbs, Finnish adds -sti:

tarkka → tarkasti = accurately, carefully
nopea → nopeasti = quickly
selvä → selvästi = clearly

So:

kaikki tähdet oli piirretty tarkasti
= all the stars had been drawn accurately / carefully

Could we change the word order to Katsomalla karttaa opin uuden tähdistön nimen…? Would the meaning change?

Yes, you can say:

Katsomalla karttaa opin uuden tähdistön nimen, jossa kaikki tähdet oli piirretty tarkasti.

The basic meaning stays the same: you learned the name by looking at the map.

Word order in Finnish often affects focus/emphasis, not core grammar:

Opin uuden tähdistön nimen katsomalla karttaa…
→ starts by highlighting the result (I learned the name).
Katsomalla karttaa opin uuden tähdistön nimen…
→ starts by highlighting the method (By looking at the map…).

Both are correct; choose based on what you want to emphasize first.