Star profile

Alfirk

Beta Cepheus · Cepheus

Variable star

3D likeness based on its real data · class B · ~15,000 K

What is Alfirk

Alfirk, beta Cephei, is the prototype of an entire class of variable stars —the 'Beta Cephei' variables— that pulse on hourly scales through contractions of their own atmospheres. She is blue, hot and immense, 685 light-years away: her light set out at the close of the Middle Ages, when Constantinople was still Byzantine. The name comes from the Arabic «al-firq», 'the flock'.

Where it is and when to see it

Alfirk lies in the northern celestial hemisphere. It is visible to the naked eye under a dark sky. Its best month of the year is October, when it culminates around midnight.

From London it never sets and culminates about 71° up.
From New York it never sets and culminates about 60° up.
From Sydney it never rises above the horizon.

It can be seen from anywhere north of 19° S.

It ranks no. 3 in brightness among the 95 stars of Cepheus in our catalogue. To find it, start from Alderamin, the brightest: it lies about 8° away (a fist at arm's length covers about 10°).

The light you see today left it about 690 years ago.

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Astronomical data for Alfirk

Constellation: Cepheus
Apparent magnitude: 3.23
Distance: 685.3 light years
Coordinates (J2000): RA 322.165° · Dec 70.561°
Catalogue: HIP 106032 · HD 205021

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Other stars in Cepheus

Cepheus has 95 stars in Stelvia's catalogue. Here are a few of them.

See all 95 stars in Cepheus