Rafferty Was Rong

You’ve been as constant as a Northern Star
The brightest light that shines

Right Down The Line
Gerry Rafferty

Back when the song was popular I used to use that lyric as an example of “Bad Astronomy”TM. (Yeah, yeah – I know. Dating myself.) The Northern Star, Polaris, is neither the brightest star, nor is it “constant”. It’s light varies over a period of 4 days.

I had to stop using that line because Polaris seemed to be on the verge of stopping that kind of activity. It was becoming more constant.

Polaris is a well known Cepheid variable, but its periodic brightness variations have been steadily decreasing in amplitude for the last hundred years. Around the beginning of the 20th Century, Polaris’ brightness fluctuated every four days by 10%. Only ten years ago this variation had dropped to 2%, leading astronomers to believe this steady decline in the variability of the star was about to end.

Guess what. It’s started up once more.

That was until recent observations uncovered an increase in variability to 4%. Polaris is an odd star in that it is a Cephid variable with a declining variability, and now astronomers are baffled as to why the brightness fluctuation has been revived.

One wishes it would make up it’s mind!

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