Meet a star / Perseus

Atik

Atik is a blue-white star, far hotter than the Sun, in the constellation Perseus. It is a giant: a star that has used up the hydrogen in its core and swollen up.

A drawing in the star's own colour, worked out from its measured colour index. It is not a photograph.

How far

1,100 light years

The light you see from Atik tonight set off about 1,100 years ago. Everything we know about it is that much out of date.

Distances this great are hard to measure, and this one could be out by a fifth or more.

How bright

3,000 Suns

It gives out 3,000 times as much visible light as the Sun. It can be seen by eye away from bright lights.

Astronomers put its brightness in our sky at magnitude 3.84. Smaller numbers are brighter, and the faintest stars the eye can see are about 6.

How hot

About 26,000 K

That is the temperature of its surface, worked out from its spectral type, B1III, with a standard table of how hot stars of each type are. It is a guide and not a measurement, and could be out by a tenth or so. Its colour alone would suggest only about 9,900 K. Dust lying between us and the star reddens its light, the way the air reddens the setting Sun, so for this star the type is the better guide. The Sun's is 5,772 K. Hotter stars are bluer and cooler stars are redder, the same way a poker in a fire goes from red to white.

Atik, as it looks through the dustThe Sun

In your sky now

Working it out…

Its names

Its own name
Atik
By constellation (Bayer)
Omicron Persei
Hipparcos catalogue
HIP 17448
Henry Draper catalogue
HD 23180
Spectral type
B1III

Where this comes from

Distance, brightness, colour and spectral type are from the HYG star database, version 4.4, by David Nash, shared under a Creative Commons Attribution-ShareAlike 4.0 licence. Its distances are those measured by the Hipparcos satellite. The temperature is read from the spectral type with the table of Pecaut and Mamajek (2013), and the words are written for this site.

To read more: Colour and brightness, How stars live and die, Measuring distance.