# What Is Apparent Magnitude?

> Why is a magnitude-1 star brighter than magnitude 5? And why does smaller mean brighter?

Apparent magnitude measures how bright a star looks from Earth: the smaller the number, the brighter the star. Magnitude 1 is brilliant, magnitude 6 is about the naked-eye limit, and none of it depends on the star’s actual distance.

URL: https://astarnamed.com/guides/apparent-magnitude · Category: astronomy · Published: 

## A ruler that runs backwards

Magnitudes trace back to the ancient Greek ranking (brightest = 1st, faintest = 6th) and were later made mathematical: one magnitude step equals about 2.5× in brightness. The scale now extends negative — Sirius, the brightest star in the night sky, is about magnitude −1.5.

- **Magnitude 1** — very bright — e.g. Regulus at 1.36
- **Magnitude 3** — bright, visible from the city
- **Magnitude 5** — fainter — needs a decent dark sky
- **Magnitude 6** — naked-eye limit under dark skies

## What it does not tell you

Apparent magnitude is not intrinsic brightness. A far, blazing star can look identical to a close, dim one. Once you own a star, its magnitude tells you how easy it will be to spot: the lower the number, the brighter the star — roughly magnitude 3 and brighter is visible from a city. Your certificate and star page carry its true value.

**Browse Stars by Brightness ✦** — https://astarnamed.com/stars/

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

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# 视星等(Apparent Magnitude)是什么?

> 为什么 1 等星比 5 等星亮?为什么数字越小越亮?

视星等衡量一颗星从地球上看有多亮:数字越小越亮,1 等为亮星,6 等约是肉眼极限。它只描述"看起来"的亮度,与恒星真实距离无关。

## 一把倒过来的尺子

视星等源自古希腊的星等划分(最亮 1 等、最暗 6 等),后来被数学化:每差 1 等,亮度差约 2.5 倍。数值范围也扩展到负数——全天最亮的恒星天狼星约 −1.5 等。

- **1 等** — 很亮,如轩辕十四(1.36 等)
- **3 等** — 明亮,城市夜空中也能看见
- **5 等** — 较暗,需要较好的夜空
- **6 等** — 肉眼极限,需无光害环境

## 它不告诉你的

视星等 ≠ 绝对亮度。一颗远而亮的星(如某些超巨星)看起来可能和一颗近而暗的星差不多。收到一颗星之后,它的星等能告诉你"夜空中容不容易找到它":数字越小越亮,城市夜空也能看见的约在 3 等以内——证书与星页上都会标注这颗星的真实星等。

**按亮度浏览恒星 ✦** — https://astarnamed.com/stars/

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