# What Is a Light-Year?

> A light-year is a measure of distance, not time — and a very large one.

A light-year is the distance light travels in a vacuum in one year: about 9.46 trillion kilometers (5.88 trillion miles). The “year” names the travel time, but the unit itself is a length — like “man-hours” describe work, not people.

URL: https://astarnamed.com/guides/light-year · Category: astronomy · Published: 

## How fast is light?

- **1 second** — 299,792 km — 7.5 times around Earth
- **8 min 20 s** — Sunlight reaches Earth
- **4.24 years** — From Proxima Centauri, our nearest star
- **1 light-year** — ≈ 9.46 trillion km

## Why we use light-years

For stars, kilometers become an unreadable string of zeros. Light-years keep cosmic numbers graspable — and carry a romantic bonus: the light you see left the star N years ago, so looking at stars is looking back in time.

## How far away is your star

The stars in our catalog mostly sit between tens and hundreds of light-years. Regulus in Leo, for example, is 79.3 light-years away — what you see of it today left 79.3 years ago. Every star page shows the real distance.

## FAQ

**What is the difference between a light-year and a year?**

A year measures time; a light-year measures distance — how far light travels in one year.

**See the Sky of That Moment ✦** — https://astarnamed.com/find

> See the real star data behind every memorial star → https://astarnamed.com/our-data

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# 光年是什么?

> 光年不是时间单位,而是距离单位——而且是个特别大的距离。

光年是光在真空中一年走过的距离,约 9.46 万亿公里(5.88 万亿英里)。名字里的"年"是时间单位,但整个词描述的是长度——就像"人公里"描述的是路程一样。

## 光有多快?

- **1 秒** — 299,792 公里——绕地球 7.5 圈
- **8 分 20 秒** — 从太阳到达地球
- **4.24 年** — 从最近的恒星(比邻星)到达地球
- **1 光年** — 约 9.46 万亿公里

## 为什么用光年

对恒星而言,公里这个单位会变成一串读不完的零。光年把"天文数字"变回可感的尺度,还附带一层浪漫含义:你看到的星光,是它在 N 年前离开恒星表面时发出的——看星即回望过去。

## 你的星有多远

我们星库里的恒星大多在几十到几百光年之间。例如狮子座的轩辕十四(Regulus)距地球 79.3 光年——你现在看到它的样子,是 79.3 年前的样子。每颗星的资料页都会标注真实距离。

## FAQ

**光年与年的区别?**

年是时间单位;光年是距离单位——光一年内走过的路程。

**回看那一刻的星空 ✦** — https://astarnamed.com/find

> 看每一颗纪念星背后的真实星表数据 → https://astarnamed.com/our-data