# Caph (Beta Cassiopeiae)

Caph (Beta Cassiopeiae) is a star in the constellation Cassiopeia, magnitude 2.3.

**The tip of Cassiopeia’s W — a fast-spinning white giant that pulses every two and a half hours.**

Caph is Arabic for “palm”. Long ago the whole W of Cassiopeia was al-Kaff al-Khadib, “the stained hand”, a hand dyed with henna, belonging to a vast figure whose head was the Pleiades. Over time the name shrank to this one star.

Caph is a yellow-white giant that has just finished burning hydrogen in its core. Once an A-type star of about twice the Sun’s mass, it is cooling and expanding on its way to becoming a red giant — a brief stage, so stars like it are uncommon. It pulses every 2.5 hours, a Delta Scuti [variable star](https://astropilot.space/glossary/variable-star), and the fourth-brightest of its kind after Denebola, Vega and Altair.

It also spins fast, at about 92 per cent of the speed that would break it up, turning more than once a day. Its equator bulges about 24 per cent wider than its poles, and the poles are some 1,000 kelvin hotter. We see it almost pole-on.

Caph (Beta Cassiopeiae) is 55 light-years away: the light we see from it set off in 1971, around the time Apollo 11 landed on the Moon.

## Did you know?

- **The first Guide.** With Alpheratz and Algenib it is one of the “Three Guides”: a line from Caph through Alpheratz runs south to where the Sun crosses the celestial equator at the equinoxes.
- **Tycho’s Star.** In 1572 a brilliant new star — the supernova now called Tycho’s Star — blazed out about five degrees north-west of Caph.
- **The charioteer himself.** In China Caph is the legendary charioteer Wang Liang himself, and the other stars of his asterism are his four horses.

A white 2nd-magnitude star at the western end of Cassiopeia’s W. Draw a line south from it: you reach Alpheratz and then Algenib at the edge of the Great Square, all three almost exactly in a row.

## When and where to see it

It is best placed in the evening sky around October, when it crosses the meridian at about 10 pm local time (around midnight in September). It can be seen from everywhere north of 31°S and never sets north of 31°N.

At its highest it stands 81° up from 50°N, 66° up from 35°N, 31° up from the equator, below the horizon from 35°S.

## Facts

- Type: Star
- Constellation: Cassiopeia
- Designations: Beta Cassiopeiae, β Cas, 11 Cas, HR 21, HD 432, HIP 746
- Magnitude: 2.3
- Position: RA 0h 9.2m, Dec +59° 9′ (J2000)
- Spectral type: F2III
- Colour: yellow-white (B−V 0.34)
- Distance: 55 light-years
- Discovered: Known since antiquity

Open AstroPilot to see when Caph (Beta Cassiopeiae) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view. https://astropilot.space/object/caph