Seven Stars and Seven Stones

[Iargwath]

Unfinished Tales has a chapter called A Description of The Island of Numenor. This chapter states that the island of Numenor itself is shaped like a five-pointed star (hence the five pointed stars in the emblem of Elendil).

The land of Numenor resembled in outline a five-pointed star, or pentangle with a central portion some two hundred and fifty miles across, north and south, and east and west, from which extended five large peninsular promontories.

Futher research indicates that the seven stars represent each of the Palantir that Elendil brought from Numenor.
This page has good information on the Emblem of Elendil.
Note: scroll down to sub-headding THE THIRD AGE: ARNOR AND GONDOR
Quote from 'Unfinished Tales' Part 2: ch 1