Blue-white main-sequence star · Perseus

Algol

Also known as: β Persei (β Per), HIP 14576

mag 2.190 light-years

About

Algol (β Persei) is a blue-white main-sequence star of magnitude 2.1 in Perseus, about 90 light-years away.

Algol is in the constellation Perseus.
Best evenings: around late December it is highest at about 9 pm (10 pm in summer time); a month earlier, two hours later.
Where on Earth: it is seen well, at least 10° up, from north of 39° S.

When it rises and sets tonight, how high it climbs and how much the Moon gets in the way are worked out in your browser for your place.

EyesEasy, even from town.
Binoculars (10×50)A sharp point; binoculars bring out its colour and the fainter stars around it.
Telescope (6–8 inch)Still a point of light at any magnification — stars are too far away to show a disc. Low in the sky, bright stars twinkle and flash colours.

Stars look the same in any instrument: brighter and sharper, but never bigger.

Proper name	Algol
Designation	β Persei (β Per)
Hipparcos number	HIP 14576
Type	Blue-white main-sequence star
Spectral type	B8V
Colour	WhiteB−V colour index 0.00
Magnitude	2.1The smaller the number, the brighter.
Distance	90 light-yearsThe light you see left it around 1936.
Proper motion	0.003″ per year across the sky
Constellation	Perseus
Right ascension (J2000)	03h 08m 10.1s
Declination (J2000)	+40° 57′ 20″