Whenever a municipality or territory is endangered as specified in Section 7-5-1, upon written petition, describing the property sought to be acquired, and signed by not less than three-fourths of the electors of that municipality or territory, and by the owners in fee simple of not less than one-half in value of the remaining territory within the limits of that municipality or territory, the corporate authorities of that municipality, or the trustees of the lands held as a common, by ordinance, may authorize acquisition of the title to the real estate described in the petition.
     Upon the passage of the ordinance, that municipality or the inhabitants of that territory may acquire the title to the real estate described in the petition and ordinance, either by gift or by purchase. A deed of conveyance to the municipality by its corporate name, or to the trustees of the land held as a common, shall vest the title to this real estate for the purposes of this article.