investigated M40

Did some research for Sue. She asked, "Is there a reasonably accurate measurement of the distance in light years between the 'double stars' in M40?"

I found notes at wikipedia on Messier 40 (M40): In 1991 the separation between the components was measured at 51.7", an increase since Messier's time. Data gathered by astronomers Brian Skiff (2001) and Richard Nugent (2002) strongly suggested that M40 is merely an optical double star rather than a physically connected system.

I found other interesting details on SEDS: The position angle has also changed since first report in 1863.

The Lick Observatory Index Catalog lists the spectrum of the primary as G0, while SIMBAD lists them as A (HD 238107), spectrum G0 and B (HD 238108), spectrum F8. Skiff gives their spectra as K0III and G0V (Skiff 2001).

If the primary is a main sequence star, then Skiff said the distance was approx. 300 light years.

In 1998, Feltz evaluated the Hipparcos data to yield a distance of 510 light years.

Nugent in 2002 reevaluated the spectral types provided by Skiff to derive spectroscopic distances of 1900 +/- 750 and 550 +/- 230 light-years, respectively.

He published this, in fact, Journal of the Royal Astronomical Society of Canada, Vol. 96, p.63, in 04/2002. Huh!