夜空にキラキラ光る星たち。どうして光って見えるの？どうしてまたたいているの？
左にしつもん、右にやさしいせつめいで、星空さんぽをもっと楽しくしよう。
Stars shine and sparkle in the night sky. Why do we see their light? Why do they twinkle?
With questions on the left and easy answers on the right, night-sky walks become even more fun.
⭐夜空の光Lights in the sky🌌銀河・宇宙Galaxy & space🔭星の観察Star watching🧭方角と星座Directions & constellations
1QUESTION
星って何？ 小さなライトみたいに見えるけど…What is a star? It looks like a tiny light…
夜空に光っている、たくさんの点の正体。What are all those little shining dots in the night sky?
他の星はものすごく遠くにあるから、
どれも小さな光の点に見えているんだよ。
A star is a huge ball of hot gas that is very, very far away.
Our Sun is one of those stars. It’s just a star that is very close to Earth.
Other stars are so far away that we can only see them
as tiny points of light in the sky.
🌞昼は太陽の光が強すぎて、ほかの星の光が見えなくなっているだけなんだ。In the daytime, the Sun’s light is so strong that we can’t see the light from other stars.
2QUESTION
どうして星はキラキラ「またたいて」見えるの？Why do stars look like they are twinkling?
ついたり消えたりしているようにも見えるね。Sometimes they look like they are turning on and off.
その結果、私たちには光が強くなったり弱くなったりして見えて、
「キラキラまたたいている」ように感じるんだよ。
Star light passes through many layers of air before it reaches us.
That air is moving and has different temperatures in different places,
so the light’s path keeps changing a little bit.
Because of this, the light looks stronger and weaker again and again,
and we see it as a twinkling star.
🔥ろうそくの火がゆらゆらするのを、遠くから見ている感じをイメージしてみると分かりやすいよ。Imagine looking at a candle flame from far away as it moves and shakes. That is like a twinkling star.
3QUESTION
どうして夜じゃないと星が見えないの？Why can we see stars only at night?
昼にも星はあるのに、目では見えないのはなぜ？Stars are there in the daytime too, so why can’t we see them?
夜になると、太陽の光が地球の反対側からしか来なくなるので、
空が暗くなり、星の光がはっきり見えるようになるんだ。
In the daytime, the Sun’s light is very strong, so the whole sky becomes too bright.
The stars’ weak light gets hidden by this brightness and we can’t see it.
At night, the Sun is on the other side of Earth, so the sky becomes dark,
and the stars’ light stands out clearly.
👀明るい部屋では小さなライトが見えにくいけど、電気を消すとよく見えるのとにているね。It’s like a small light in a bright room: you see it better when you turn the big lights off.
4QUESTION
星座（せいざ）って、ほんとうに「その形の星」が並んでいるの？Are the stars in a constellation really making that picture?
オリオン座・さそり座など、動物や人の形をしている星たち。Orion, Scorpius… They look like people or animals in the sky.
でも、昔の人たちは、星のならびを動物や神さまの形に見立ててお話を作り、
方角や季節を知る目じるしとして使ってきたんだ。
A constellation is made when people draw lines between stars
and pretend it looks like a shape, such as a person or an animal.
In reality, the stars are very far apart and not really connected.
Long ago, people used these shapes to make stories,
and as markers for directions and seasons.
✏️自分だけのオリジナル星座を作って、星を線でむすんで絵にしてみるのも楽しいよ。Try drawing your own constellation by connecting stars with lines and making your own picture.
5QUESTION
流れ星（ながれぼし）は、星が落ちてきているの？Is a shooting star really a star falling down?
一瞬でスッと消えてしまう光の線。A bright line of light that disappears in a moment.
とても速く動いて、燃えつきてしまうので、
空には一瞬だけ光る線として見えるんだ。
A shooting star is really a tiny rock or dust from space
that hits Earth’s air and burns bright.
It is not a big star falling down.
It moves very fast and burns up quickly,
so we only see it as a short, bright line in the sky.
🌠明かりの少ない場所で、しばらく空を見上げていると、ラッキーなら流れ星が見えるかもしれないよ。In a dark place with few lights, look up at the sky for a while. If you’re lucky, you might see a shooting star.
6QUESTION
星の明るさや色がちがうのはどうして？Why do stars have different brightness and colors?
とても明るい星や、すこし赤っぽい星があるね。Some stars are very bright, and some look a bit red.
色は、星の温度のちがいによるもの。
とても熱い星は青白く、少し冷めた星は赤っぽく見えるんだ。
Brightness depends on the star’s size, heat, and distance from Earth.
Big, hot stars or stars close to Earth look brighter to us.
Color comes from the star’s temperature.
Very hot stars look blue-white, and cooler stars look a little red.
🎨双眼鏡で明るい星を見て、白っぽいか・青っぽいか・黄色っぽいか、色を観察してみよう。Use binoculars and look at bright stars. Do they look white, blue, or yellow? Try to notice the colors.
7QUESTION
星って、動いていないように見えるけど、本当はどうなの？Stars look still in the sky. Are they really not moving?
夜空の星は、ずっと同じ場所にいるように見えるね。They seem to stay in the same place all night.
かわりに、地球が自分で回っている（自転）ので、
私たちから見ると星が東から西へ動いているように見えるんだよ。
Stars are really moving through space too.
But they are so far away that we can’t see their small motions.
Instead, Earth is spinning (rotating),
so it looks to us like the stars are moving from east to west.
🕒同じ星を、夜の早い時間と夜おそくに見くらべてみると、位置が少し動いていることがわかるよ。Look at the same star early at night and again later. You’ll see it has moved to a different place in the sky.
8QUESTION
星と惑星（わくせい／ほし）は、どうちがうの？What is the difference between a star and a planet?
どっちも「ほし」って呼ばれることが多いね。In Japanese, both are often called “hoshi (star).”
夜空に見える少し大きめで、あまりまたたかない光は、
惑星であることが多いよ。
A “star” (like the Sun) is an object that makes its own light.
A “planet” is an object that goes around a star
and only shines by reflecting the star’s light.
In the night sky, a slightly bigger light that doesn’t twinkle much
is often a planet.
🔭天体アプリを使うと、この明るい点が「星」なのか「惑星」なのか、名前まで知ることができるよ。With a sky-watching app, you can learn if a bright point is a star or a planet, and even see its name.
9QUESTION
ほかに、星についてどんな「なぜ？」があるかな？What other “whys” about stars can you think of?
星空は、質問の宝箱。The night sky is a treasure box of questions.
IDEAS
たとえば、こんな「なぜ？」もあるよ：
天の川（あまのがわ）は、何があつまってできているの？
星が生まれる場所・星が終わるときって、どんなようす？
北極星は、どうしてほとんど動かないように見えるの？
都会と田舎（いなか）で、見える星の数がちがうのはなぜ？
For example, you might ask:
What is the Milky Way made of?
What happens when a star is born, and when a star dies?
Why does the North Star look like it hardly moves?
Why can we see more stars in the countryside than in big cities?
📝星空を見上げながら思いついた「なぜ？」をノートにメモして、あとで図鑑や天文の本で調べてみよう。Write your “why” questions in a notebook while you look at the sky, then check books or websites about space later.