Pole Star Pulses

[Andy Nimmo]

Hi Fraser,

I’ve written a book called "Universal Detectives" on the history of cosmology from the merest potential microbe 4.4 billion years ago up to human knowledge at 31st March this year and am making it available on CD to those interested, however one paragraph has had to read:

1990 Changes in the Pole Star
Our Pole Star is a Cepheid Variable that astronomers believe has been pulsing for 40,000 years. It was found to pulse in 1896 and did so from then until the mid 1970s at about 5 kms in and out per second. By 1987 this had slowed to 1.5 kms per second and by 1990 to only 0.5 kms per second. At this rate of slowing it was forecast it would cease to pulse altogether by 1992. Does anyone know if it still pulses? If so, do let me know and I'll put this in the next Update of Universal Detectives.

---as I not only don’t know the answer, but have been unable to find it. Perhaps one of your question-answerers knows? If so, I shall certainly acknowledge their help in my update, probably around the end of September.

Best wishes, Andy Nimmo.

[Andy Nimmo]

It seems the answer to this question was published by space writer Neil English, in the February issue of Astronomy Now, that I missed. The Pole Star is still pulsing but by such a small magnitude as to be invisible to the human eye. At 430 ly away it is the nearest Cepheid Variable star to us, and seems to be in the process of changing from one kind into another. In 1997 a team of African and American theoreticians forecast that it ought to have a diameter of 46 solar radii, and in 2000 Dr Tyler F. Nordgren of the US Naval Observatory near Flagstaff, Arizona, and colleagues combined 3 telescopes into a sensitive interferometer and found that they were correct. Its diameter is 32 million kms. The African and American astronomers’ theory says it should now develop to pulse over around 5.7 days. It is a member of a group of at least three stars, possibly as many as 7, orbiting each other. - Andy. :)

[VanderL]

Thanks Andy,

Fascinating stuff, that would make it a very strange star in a very strange environment. Do you have any references where I could see why they think it is possibly part of a seven star "ensemble".
It has always puzzled me why there are so many multiple star systems, because these systems should be very unstable. Success with your writing,

Cheers.

[Guest_Andy Nimmo]

Hi VanderL,

I understand that Sky Catalogue 2000.0 lists seven stars, but that 4 may turn out not to be associated with the main 3, perhaps just in the line of sight.

The only actual reference I have is the article, "Pole Position" by Neil English in this February's Astronomy Now magazine - for as you'll gather I didn't know the answer myself when I posed the question. Indeed, it was as a result of having done so that a friend in ASTRA - the Association in Scotland To Research into Astronautics - was kind enough to bring the article to my attention.

Best wishes, Andy. :rolleyes: