Smaug is the star around which Ancalagon orbits.

In the Exile's navigational catalogues, it goes by the designation GSC ZH101159.2+152219.6. It is located at a distance of 662 pc from Sol. The star is currently positioned 1.12 degrees further spinwards around the disc; the extra distance is accounted for by Smaug's slight elevation above the median galactic plane. The star's space velocity components are classically thin-disc in character, which is consistent with its relatively young age. (From Earth, it would be seen in the region of the sky associated with the constellation of Bootes. However, due to its distance, Smaug is not visible to the naked eye from Sol.)

In classification terms, it's basically a textbook example of an F2 Main Sequence object.

It has an effective temperature of 7,050 K. It weighs in at 1.45 solar masses. Its diameter is 1.4 solar radii. It has a luminosity of 3.8 solar luminosities. As is typical of F stars, Smaug's spectrum peaks at shorter wavelengths than Sol's - Smaug is substantially more luminous in the ultraviolet than Sol is.

(This, of course, had an impact on the ADC's genetic adaptation program - old-style skin struggled with Smaug-light. The early colony suffered extensively with maladies ranging 'merely' from sunburn, all the way through to malignnant melanomas. This is, incidentally, how the star acquired its draconically-inspired name - after all, its light burns!)

Smaug has a rotation period of 35 terrestrial days. It is moderately prone to sunspots and flares, although its chromospheric activity is well within safe ranges. Similar to Sol, Smaug has a cycle of varying sunspot activity, although in Smaug's case, this cycle runs for 8 years rather than Sol's 11-year period.

In terms of chemical composition, it is somewhat more enriched with heavy elements than Earth's Sun. (For the cognoscenti, it has [M/H] = +0.12.) The star itself is 2.2 billion years old - interestingly, this actually means that Smaug is approaching the end of its main sequence lifetime. It is expected to begin expanding into a red giant in less than 500 million years. Given the relatively-short time that the star has left to live, had circumstances been more normal, Ancalagon would never have been settled. However, the climate collapse of Old Earth forced a lot of hands, with historic consequences.

(Technical note: I've depicted Smaug as a lot more blue than it would probably look. It would probably be much more white than I've shown it here. However, I like pale blues, and also I wanted to emphasise that Smaug's surface and light is hotter/bluer than the Sun's.)