Learn Hardcore Japanese: tenmongaku no hon toka utyuu no syasinsyuu toka wo tosyokan de karite yomu uti ni, yozora no hosi no miekata ga sukosi kawatte kimasita. - As I borrowed and read astronomy books and space photo collections from the library, the way I saw the stars in the night sky changed a bit.

Functionally, の here is similar to English of or the noun‑noun compounds like “astronomy books, space photobook” etc. It doesn’t always mean literal possession; it’s often just “N1 is a characteristic/context of N2”.

What nuance does とか have in 天文学の本とか宇宙の写真集とか? How is it different from や?

とか after a noun roughly means “and stuff like / and things like”. Using it in a list like:

天文学の本とか宇宙の写真集とか

implies:

“astronomy books, space photo collections, and things like that.”

Nuances:

AとかBとか:
Casual, often spoken. Feels like you’re listing examples in a loose, non‑exhaustive way.
“Things like A and B and similar stuff.”
AやB:
Also “A and B and (possibly) others”, but more neutral/standard and a bit less casual than とか. Common in writing and speech.
AとかBとかを… vs AやBを…:
Both are grammatically fine; とか just feels more conversational and “example‑ish”.

Using とか twice (本とか…写真集とか) reinforces that these are just some examples among many, not a complete list.

Why is を placed after the second とか in 天文学の本とか宇宙の写真集とかを? What exactly is marked as the object?

The を marks the entire list as the direct object of 借りて読む (“to borrow and read”).

Structurally:

天文学の本とか宇宙の写真集とか = “astronomy books, space photo collections, and things like that”
…を借りて読む = “borrow and read (them)”

So “astronomy books and space photo collections and such” is one big noun phrase, and を attaches at the end to mark that whole phrase as the object. This “put the particle after the whole list” pattern is very common in Japanese:

りんごやバナナやみかんを 買う
音楽とか映画とかを よく見る

In 図書館で借りて読む, what does the で mean? Is it “at the library” or “from the library”?

Here 図書館で literally means “at the library” (place where the actions happen):

図書館で借りて = “(I) borrow them at the library”
(図書館で)読んで could also mean “read them at the library”, but in this sentence 借りて and 読む are just a sequence of typical actions: borrow them (from the library) and read them (not necessarily at the library).

Natural English understanding is “borrow from the library and read (them)”, but grammatically で is marking the location of the action, not the source.

If you really want to emphasize source, you can use:

図書館から借りる = “borrow from the library”

But 図書館で借りる is very common and idiomatic.

Why is it 借りて読むうちに (dictionary form 読む) and not 借りて読んでいるうちに or 借りて読んでいる間に?

The dictionary form 読む here has a “habitual / repeated action” meaning:

借りて読むうちに ≈ “while (I) kept borrowing and reading them / as I went on borrowing and reading them (over time)”

Using V-dictionary + うちに is a common pattern to express “as one keeps doing V, over the course of doing V”.

If you said:

借りて読んでいるうちに
it might suggest more “during the period when I was in the middle of reading them (on that occasion)”, more like a continuous ongoing situation.

The original sentence wants to describe a gradual change over a longer stretch of time, through repeated borrowing and reading, so 借りて読むうちに fits that nuance better.

What exactly does うちに mean in this sentence? How is it different from あいだ?

うちに basically means “while (something is going on) / in the course of (doing something)” and often implies some change that happens naturally during that period.

Here:

借りて読むうちに ≈ “while I kept borrowing and reading (those books), / as I went on borrowing and reading them,”

Difference from あいだ:

V-ているあいだ（に） = “during the time (when something is happening)”
More neutral, just marks a time span.
V-dictionary / V-ているうちに =
“in the process of doing that, as time passed, (something changed / happened naturally)”

うちに strongly collocates with sentences of change, like:

日本に住んでいるうちに、日本語が上手になった。
As I lived in Japan, my Japanese got better.

In your sentence, うちに works perfectly with 変わってきました (a gradual change).

In 夜空の星の見え方が少し変わってきました, does 星の見え方 mean “how the stars look to me” or “how the stars actually look in reality”?

Literally, 星の見え方 is “the way the stars are seen / the way the stars appear”. It refers to the appearance as perceived by an observer, not some objective physical change in the stars.

So:

夜空の星の見え方が少し変わってきました。
≈ “The way the stars in the night sky look (to me) has gradually changed a bit.”

It implies:

My perspective, understanding, or sense of the stars has changed, not that the night sky itself physically transformed. The context of reading astronomy and space books supports this “change in perception/interpretation” reading.

Why use 変わってきました instead of just 変わりました? What nuance does 〜てくる add?

〜てくる here expresses a gradual change leading up to now.

変わりました = “(it) changed”
A more point‑like or completed change; neutral about the process.
変わってきました = “(it) has (gradually) come to change / has been changing (and now is different)”
Emphasizes:
- the process over time, and
- that the result of that process is relevant now.

In this sentence, 変わってきました nicely matches the idea “as I kept reading those books, my way of seeing the night sky has gradually changed (to what it is now).”

Could は be used in this sentence? For example, 夜空の星の見え方は少し変わってきました. How would that change the nuance compared to が?

Yes, は is possible:

夜空の星の見え方は少し変わってきました。

With が:

夜空の星の見え方が少し変わってきました。
Presents “the way the stars look” as new information or as the grammatical subject in a neutral statement. It feels like a simple report of what has changed.

With は:

Places 夜空の星の見え方 as the topic or contrastive element:
“As for the way the stars in the night sky look, that has changed a bit (maybe compared to something else that hasn’t).”

In isolation, both are acceptable; が sounds a bit more straightforwardly descriptive, は gives more of a topical/contrastive flavor depending on context.

Is うち in うちに a noun? Could I treat it like other nouns and say things like 読むうちの変化?

Yes, うち is originally a noun (meaning “inside, interior, within”), but in the fixed pattern 〜うちに it functions like a set expression meaning “while / in the course of”.

As a free noun, うち can mean “inside, within, one’s home, one’s group, etc.”
In V-うちに, it’s better to think of it as a grammatical pattern rather than a freely combinable noun.

Something like 読むうちの変化 is grammatically odd; native speakers wouldn’t say it that way. You’d more likely say:

読んでいるうちに起こった変化
“the changes that occurred while (I) was reading”

So: うち is technically a noun, but in this construction it’s basically part of a fixed grammar pattern 〜うちに.

Is とか considered casual? Would this sentence be okay in formal writing?

とか in the “AとかBとか” listing sense is indeed casual / conversational. It’s very natural in speech, essays, blogs, personal writing, etc.

In very formal or academic writing, you’d more likely see:

天文学の本や宇宙の写真集を…
using や instead of とか

or a more explicit phrase like:

天文学の本や宇宙に関する写真集などを…

So, the sentence as-is feels like natural spoken Japanese or casual written Japanese. For formal reports, you’d tone it down by replacing とか with や or other more formal wording.

Could you say 図書館から借りて instead of 図書館で借りて? What’s the difference?

Yes, you can say 図書館から借りて, and it’s perfectly grammatical.

Nuance:

図書館で借りて
Focuses on the place where the action happens (at the library).
Very idiomatic; people routinely say this in everyday speech.
図書館から借りて
Focuses more on the source (“from the library”) of the borrowed items.
Slightly more explicit about origin, but not necessarily more natural.

In your sentence, 図書館で借りて読むうちに… sounds very natural and is probably the more common choice. 図書館から借りて読むうちに… is also acceptable, just with a shade more emphasis on “from the library”.