夜空を見上げたとき、星が動いて見えるのはなぜ？実は星じゃなくて地球が動いているんだ。星の動きには1日の動きと1年の動きの2種類があって、この仕組みを理解すればテストの計算問題もバッチリ解ける！
地学
英語
数学
理科
その他
TOEIC
国語Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
32
•
Updated May 3, 2026
•
星座の動きと季節の関係
1 / 6
星の動きと星座の基本
君たちが夜空で見る星の動きは、実際には地球が動いているから起こる現象だよ。この「見かけの動き」をマスターすれば、理科のテストで高得点が狙える！
天球っていうのは、地球を中心とした巨大な架空の球のこと。すべての星がこの球の内側に貼りついて見えると考えるモデルで、星の位置を説明するときにめちゃくちゃ便利なんだ。
星の動きには日周運動（1日の動き）と年周運動（1年の動き）の2種類がある。日周運動は地球の自転が原因で、年周運動は地球の公転が原因だよ。
北極星は地球の地軸を北に延ばした先にある特別な星。地球が自転してもほとんど動かないから、北の空の目印として使えるんだ。
覚えておこう！ 自転→日周運動、公転→年周運動。この関係は絶対に覚えよう！
星の日周運動
日周運動は地球が24時間で1回転する自転が原因で起こる。星が東から昇って西に沈むように見える、あの動きのことだよ！
地球は24時間で360°回転するから、1時間あたり15°動く計算になる。この数字は計算問題で絶対に使うから、必ず覚えておこう。
方角によって星の動き方が違うのがポイント。北の空では北極星を中心に反時計回りに動き、南の空では東から西へ円弧を描いて動く。東の空では右斜め上に昇り、西の空では右斜め下に沈んでいくよ。
なぜ北の空だけ反時計回りなのか不思議に思うかもしれないけど、自分が北を向いて空を見上げているからなんだ。地球儀の上に立って北極点を見ながら回転する様子を想像すると分かりやすいよ。
テスト必出！ 1時間で15°という数字は絶対に覚える。計算問題で必ず使うから！
星の年周運動
年周運動は地球が太陽の周りを1年かけて回る公転が原因だよ。同じ時刻に星を見ると、季節によって見える星座が変わるのがこの現象なんだ。
冬にはオリオン座、夏にはさそり座が代表的に見えるのも年周運動のおかげ。地球が1年（12ヶ月）で360°公転するから、1ヶ月あたり30°ずつ星の位置が変わって見える。
ここで超重要な計算がある！年周運動で1ヶ月に30°、日周運動で1時間に15°動くから、30°÷15°/時間＝2時間。つまり**「星座が同じ位置に見える時刻は、1ヶ月で2時間早くなる」**んだ。
この「1ヶ月で2時間早くなる」法則は、テストで本当によく出題される。2ヶ月後なら4時間早く、3ヶ月後なら6時間早くなるよ。
最重要ポイント！ 1ヶ月で2時間早くなる法則は、年周運動の問題で必ず使う公式だよ！
例題と計算問題
実際の問題を解いてみよう！まず日周運動の計算から。ある日の午後8時に南の空にオリオン座が見えたとして、3時間後の午後11時にはどこに見える？
考え方はシンプル。星は1時間に15°動くから、3時間で15°×3＝45°動く。星は東から西へ動くから、答えは「西の方向へ45°動いた位置」だ。
次は年周運動の計算。1月15日の午後10時に真南に見えた星が、2月15日に同じ位置に見える時刻は？1ヶ月後だから2時間早くなって、午後10時－2時間＝午後8時が答えだよ。
北極星の高度も覚えておこう。北極星が地平線から見える角度は、その場所の緯度とほぼ同じ。東京（北緯約35°）では、北極星は地平線から約35°の高さに見えるんだ。
計算のコツ！ 日周運動は15°×時間、年周運動は30°×月数で計算できるよ！
まとめとテスト対策
星の動きの正体は地球の運動だということが分かったね。自転が日周運動、公転が年周運動を引き起こしている。
日周運動のポイントは「1時間で15°、東から西へ」。年周運動のポイントは「1ヶ月で30°、同じ位置に見える時刻が2時間早くなる」だ。
テストでよく間違えるのが、自転と公転の混同。自転→日周運動→1日の動き、公転→年周運動→季節の星座の変化、この関係をしっかり覚えよう。
太陽も星と同じように東から昇って西に沈むのは、どちらも地球の自転が原因だから。北極星だけは地軸の延長線上にあるため、ほとんど動かずに北の空の目印になっているよ。
テスト成功の秘訣！ 数字（1時間15°、1ヶ月30°、1ヶ月で2時間早い）と原因（自転・公転）をセットで覚えよう！
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Most popular content in 地学
Most popular content
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5
App Store
4.7/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
星座の動きと季節の関係
夜空を見上げたとき、星が動いて見えるのはなぜ？実は星じゃなくて地球が動いているんだ。星の動きには1日の動きと1年の動きの2種類があって、この仕組みを理解すればテストの計算問題もバッチリ解ける！
星の動きと星座の基本
君たちが夜空で見る星の動きは、実際には地球が動いているから起こる現象だよ。この「見かけの動き」をマスターすれば、理科のテストで高得点が狙える！
天球っていうのは、地球を中心とした巨大な架空の球のこと。すべての星がこの球の内側に貼りついて見えると考えるモデルで、星の位置を説明するときにめちゃくちゃ便利なんだ。
星の動きには日周運動（1日の動き）と年周運動（1年の動き）の2種類がある。日周運動は地球の自転が原因で、年周運動は地球の公転が原因だよ。
北極星は地球の地軸を北に延ばした先にある特別な星。地球が自転してもほとんど動かないから、北の空の目印として使えるんだ。
覚えておこう！ 自転→日周運動、公転→年周運動。この関係は絶対に覚えよう！
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
星の日周運動
日周運動は地球が24時間で1回転する自転が原因で起こる。星が東から昇って西に沈むように見える、あの動きのことだよ！
地球は24時間で360°回転するから、1時間あたり15°動く計算になる。この数字は計算問題で絶対に使うから、必ず覚えておこう。
方角によって星の動き方が違うのがポイント。北の空では北極星を中心に反時計回りに動き、南の空では東から西へ円弧を描いて動く。東の空では右斜め上に昇り、西の空では右斜め下に沈んでいくよ。
なぜ北の空だけ反時計回りなのか不思議に思うかもしれないけど、自分が北を向いて空を見上げているからなんだ。地球儀の上に立って北極点を見ながら回転する様子を想像すると分かりやすいよ。
テスト必出！ 1時間で15°という数字は絶対に覚える。計算問題で必ず使うから！
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
星の年周運動
年周運動は地球が太陽の周りを1年かけて回る公転が原因だよ。同じ時刻に星を見ると、季節によって見える星座が変わるのがこの現象なんだ。
冬にはオリオン座、夏にはさそり座が代表的に見えるのも年周運動のおかげ。地球が1年（12ヶ月）で360°公転するから、1ヶ月あたり30°ずつ星の位置が変わって見える。
ここで超重要な計算がある！年周運動で1ヶ月に30°、日周運動で1時間に15°動くから、30°÷15°/時間＝2時間。つまり**「星座が同じ位置に見える時刻は、1ヶ月で2時間早くなる」**んだ。
この「1ヶ月で2時間早くなる」法則は、テストで本当によく出題される。2ヶ月後なら4時間早く、3ヶ月後なら6時間早くなるよ。
最重要ポイント！ 1ヶ月で2時間早くなる法則は、年周運動の問題で必ず使う公式だよ！
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
例題と計算問題
実際の問題を解いてみよう！まず日周運動の計算から。ある日の午後8時に南の空にオリオン座が見えたとして、3時間後の午後11時にはどこに見える？
考え方はシンプル。星は1時間に15°動くから、3時間で15°×3＝45°動く。星は東から西へ動くから、答えは「西の方向へ45°動いた位置」だ。
次は年周運動の計算。1月15日の午後10時に真南に見えた星が、2月15日に同じ位置に見える時刻は？1ヶ月後だから2時間早くなって、午後10時－2時間＝午後8時が答えだよ。
北極星の高度も覚えておこう。北極星が地平線から見える角度は、その場所の緯度とほぼ同じ。東京（北緯約35°）では、北極星は地平線から約35°の高さに見えるんだ。
計算のコツ！ 日周運動は15°×時間、年周運動は30°×月数で計算できるよ！
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
まとめとテスト対策
星の動きの正体は地球の運動だということが分かったね。自転が日周運動、公転が年周運動を引き起こしている。
日周運動のポイントは「1時間で15°、東から西へ」。年周運動のポイントは「1ヶ月で30°、同じ位置に見える時刻が2時間早くなる」だ。
テストでよく間違えるのが、自転と公転の混同。自転→日周運動→1日の動き、公転→年周運動→季節の星座の変化、この関係をしっかり覚えよう。
太陽も星と同じように東から昇って西に沈むのは、どちらも地球の自転が原因だから。北極星だけは地軸の延長線上にあるため、ほとんど動かずに北の空の目印になっているよ。
テスト成功の秘訣！ 数字（1時間15°、1ヶ月30°、1ヶ月で2時間早い）と原因（自転・公転）をセットで覚えよう！
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
1
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Mock Exam
Quiz
Flashcards
Essay
Most popular content in 地学
Most popular content
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5
App Store
4.7/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE Knowunity AI. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user